Insect Pollination and Experimental Warming in the High Arctic

Samuel Victor Joseph Robinson

B.Sc., The University of British Columbia, 2006

A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF

MASTER OF SCIENCE

The Faculty of Graduate and Postdoctoral Studies

(Geography)

THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver) April 2014 c Samuel Victor Joseph Robinson 2014 Abstract

As climate change causes retreats in Arctic glaciers, it is important to understand the mechanics of growth and community change in Arctic plant communities. Arctic plants have been shown to respond to observed and experimental changes in temperature by altering their reproductive strategies, growth, and phenology. Researchers have used open-top chambers (OTCs) to experimentally alter the near-surface air temperatures of tundra plant communities over long periods of time, but these devices may exclude insect pollinators to flowers during crucial periods of pollen reception. Insect pollination in the context of OTCs and Arctic plants is therefore important to understand, but has been poorly researched. I altered pollination of Salix arctica, Dryas integrifolia, and Papaver radicatum inside and outside of OTCs in a High Arctic shrub community, and conducted targeted insect netting to understand the dynamics of the visiting insect community. I also conducted bowl trapping inside and outside of OTCs to gauge their effect on insect availability to receptive flowers. OTCs altered the timing of flowering in Arctic plants, and significantly reduced the availability of pollinators to available flowers. However, I found that while both warming and pollination can alter flower and seed production in the study species, pollination is largely independent of OTC warming. Early-flowering species have the potential to be most affected by OTC-induced insect exclusion. The most common visiting insects were flies of the families Syrphidae and Muscidae, with occasional bumblebees (Bombus polaris). Papaver radicatum was by far the most heavily-visited flower, and I showed that the Syrphidae visit the flower preferentially at low temperatures, likely for warmth as well as pollen. I discuss these results in context with the current literature on Arctic plant and insect communities, and make recommendations for future research.

ii Preface

• Chapters 2 and 3 are based on work conducted by Samuel Robinson and supervised by Dr. Greg Henry. I was responsible for ﬁeld work, lab work, statistics, and writing.

• No publications have yet arisen from this.

• No approval was required from the UBC Research Ethics Board.

iii Table of Contents

Abstract ...... ii

Preface ...... iii

Table of Contents ...... iv

List of Tables ...... vi

List of Figures ...... vii

Acknowledgements ...... viii

Dedication ...... ix

1 Introduction ...... 1 1.1 History of Pollination Ecology ...... 1 1.1.1 Pollination in General ...... 1 1.1.2 Studies in Arctic Pollination Biology ...... 2 1.2 Plant-Pollinator Interactions ...... 2 1.2.1 Benefits for Plants ...... 2 1.2.2 Benefits for Insects ...... 3 1.3 High Arctic Ecosystems and Climate Change ...... 3 1.3.1 The ITEX Program ...... 3 1.4 Review of Arctic Pollination and Insect Studies ...... 4 1.4.1 Confounding Effects of OTCs ...... 4 1.4.2 Insect Community Composition ...... 6 1.4.3 The Effects of Seasonality and Temperature . . . . . 6 1.5 Conclusions ...... 7 1.6 Objectives ...... 7

2 Pollen Limitation in Open-Top Chambers ...... 9 2.1 Introduction ...... 9 2.2 Methods ...... 11

iv Table of Contents

2.2.1 Site Description ...... 11 2.2.2 Plant Species ...... 11 2.2.3 Experimental Design ...... 12 2.2.4 Statistical Analyses ...... 14 2.3 Results ...... 16 2.3.1 Flower Response ...... 16 2.3.2 Seed Response ...... 17 2.4 Discussion ...... 18 2.4.1 Salix arctica ...... 18 2.4.2 Dryas integrifolia ...... 19 2.4.3 Papaver radicatum ...... 20 2.5 Conclusions ...... 22 2.6 Figures and Tables ...... 24

3 Eﬀects of Open-Top Chambers on Flowering Patterns and Potential Insect Visitation ...... 39 3.1 Introduction ...... 39 3.2 Methods ...... 41 3.2.1 Flowering Community ...... 41 3.2.2 Insect Community ...... 41 3.2.3 Statistical Analyses ...... 42 3.3 Results ...... 44 3.3.1 Flower Availability ...... 44 3.3.2 Insect Community ...... 45 3.3.3 Interaction Rates ...... 46 3.4 Discussion ...... 47 3.4.1 Flower Availability ...... 47 3.4.2 Insect Community ...... 49 3.5 Conclusion ...... 54 3.6 Figures and Tables ...... 56

4 Conclusions ...... 68

Bibliography ...... 72

Appendix

A Model Fitting ...... 90

v List of Tables

1.1 Summary of studies ...... 5

2.1 Experimental Design ...... 37 2.2 Flower Response ...... 38 2.3 Seed Response ...... 38

3.1 Tests for flower response to warming ...... 65 3.2 Differences in OTC and contol catches ...... 66 3.3 Ranking of Visitors ...... 66 3.4 Total flower-insect interactions ...... 67

A.1 Model Parameters ...... 90 A.2 Flower Model Selection ...... 91 A.3 Seed Model Selection: Part 1 ...... 92 A.4 Seed Model Selection: Part 2 ...... 93

vi List of Figures

2.1 Location Map ...... 25 2.2 Site Photo ...... 26 2.3 Salix arctica (Pall) ...... 27 2.4 Dryas integrifolia (Vahl) ...... 28 2.5 Papaver radicatum (L.) ...... 29 2.6 Flower output from hand-pollinated and warmed plants . . . 30 2.7 Flower output from pollen-manipulated plants outside warming treatments ...... 31 2.8 Flower output from warmed and control D. integrifolia . . . . 32 2.9 Seeds per flower and seed mass per flower from hand-pollinated and warmed plants ...... 33 2.10 Seeds per flower and seed mass per flower from pollen-manipulated plants outside warming treatments ...... 34 2.11 Average seed mass and germinability from hand-pollinated and warmed plants ...... 35 2.12 Average seed mass and germinability from pollen-manipulated plants outside warming treatments ...... 36

3.1 Stellaria longipes Goldie ...... 56 3.2 Ordination of OTC and control ﬂower communities ...... 57 3.3 Flower densities ...... 58 3.4 Ordination of OTC and control insect communities ...... 59 3.5 Bowl trap catches (Time Series) ...... 60 3.6 Bowl trap catches (Total) ...... 61 3.7 Net catches (Time Series) ...... 62 3.8 Net catches (Total) ...... 63 3.9 Factors inﬂuencing Papaver radicatum interaction rate . . . . 64

vii Acknowledgements

This work was funded by the National Science and Engineering Research Council of Canada (NSERC), ArcticNet, Polar Continental Shelf Program (PCSP), the Northern Scientific Training Program (NSTP), the Canadian International Polar Year (IPY - CiCAT), and the University of British Columbia. Permission for research was granted from the Nunavut Depart- ment of Environment, and the use of the buildings at Alexandra Fiord was granted by the Royal Canadian Mounted Police (RCMP). I foremost wish to thank Dr. Greg Henry for his help, advice, and encouragement during the last three years. Thank you to all of my field assistants who have helped me during the summers of field work, notably Christo- pher Greyson-Gaito, Doug Curley, Darcy McNicholl, Meagan Grabowski, and Matt Huntley. I thank Anne Bjorkmann for her statistical help and practical advice. Thank you to Fred Stride, for letting me continue to play in UBC Jazz Ensemble I throughout the past three years, and exercise a completely different part of my brain! I thank my committee members, Dr. Elizabeth Elle and Dr. Roy Turk- ington, for their support and direction. I also thank Dr. Marwan Hassan for his support and encouragement. Finally, I wish to thank my parents and my brothers for all of their love and support during my M.Sc. I can never thank you enough for how you’ve supported me.

viii Dedication

This work is dedicated to the memory of the people killed during the crash of First Air Flight 6560 on August 20, 2011, in Resolute Bay, Nunavut.

ix Chapter 1

Introduction

Pollination of flowering plants by insects (entomophily) in Arctic ecosystems is poorly understood. Visitation of flowers is beneficial for both the insects that visit them, as well as the plants, and is essential for fertilization and production of seeds in many plants. Climate change has already begun to alter plant community composition in the Arctic, and will continue to alter it into the next centuries. Understanding the speed and extent of these changes partially depends on their seed production. However, very few studies have been conducted that have identified changes in insect communities that the plants are associated with. In this literature review, I will examine the research that has currently been conducted on Arctic pollination biology, and the study of climate change effects on plant and insect communities. Finally, I will outline my specific research goals.

1.1 History of Pollination Ecology

1.1.1 Pollination in General Pollination of plants has been examined since antiquity by natural philoso- phers such as Virgil (and certainly as much by agrarians), but Rudolf Cam- erarius (1665-1721) is generally credited with the first studies of the sexu- ality of plants (Faegri and Van der Pijl, 1979). However, Camararius only examined self-fertilization, and Joseph Kölruter(1733-1806) and Christian Sprengel (1750-1816) were the first to examine pollination of flowers by insects (Proctor et al., 1996), and found that many plants required insect pollinators to obtain full seed set (fully-formed, fertile seeds). Charles Dar- wins work built on the concepts laid down by Kölruterand Sprengel in his observations of numerous floral structures and pollination techniques, and suggested a mechanism (natural selection) by which the structure of flowers could ultimately be controlled by their interactions with pollinators (Darwin, 1859, 1862). His work also lead to the general thesis that “nature abhors self- fertilization” (Waser and Ollerton, 2006). This hypothesis (“Darwins Law”) continued to dominate literature on plant-pollinator interactions until the

1 1.2. Plant-Pollinator Interactions early 1900s.

1.1.2 Studies in Arctic Pollination Biology After Darwins publication of Species and Orchids, naturalists in the High Arctic such as Aurivillius noted that flowers such as Pedicularis lanata and P. hirsute appeared to be completely self-pollinating in stark contrast to “Darwins Law (Kevan, 1973a). Other authors continued this trend into the 20th century (Warming, 1888; Mathiesen, 1921), and the hypothesis that stressed environments, such as the High Arctic, favoured self-fertilization continued. This was generally accepted until the work of Chernov (1966, 1985) and Hocking (1968) revealed that insect pollination was far more common than previously thought. Kevan (1972b) examined this in even greater detail by using acetate cones and netting to exclude pollinators, demonstrating dependence (and independence) of several pan-Arctic flowering plants on insect visitation. In recent years, plant-pollinator interactions in the High Arctic have seen an even greater interest in the scientific community, in the face of global climate change and an increased interest in networks and “connectivity in species interactions (Elberling and Olesen, 1999; Lundgren and Olesen, 2005; Hegland et al., 2009).

1.2 Plant-Pollinator Interactions

1.2.1 Benefits for Plants It is well known that plants benefit from insect visitation. Visitation of flowers by insects, particularly bees and flies, has been shown to be essential to fertilization and fruit formation in many species. Many families of plants have self-incompatibility mechanisms that do not allow pollen from the same plant to fertilize itself (autogamy, or selfing). Transfer of pollen between individuals (heterogamy or outcrossing) can be facilitated either by wind or by pollinating animals such as insects. This outcrossing increases genetic variation within populations, meta-populations, and contributes to ongoing process of natural selection by allowing gene transfer. This is also important in the development of resilient genotypes which can withstand environmental change, and to avoiding the pairing of deleterious alleles (in- breeding) (Proctor et al., 1996). Pollinating insects are often a much more efficient mechanism because they direct pollen transfer directly to flowers, often to individuals of the same species, thus reducing the amount of pollen required by a plant to produce a successful mating. This has been found

2 1.3. High Arctic Ecosystems and Climate Change to be essential in pollen-limited Arctic plants such as Saxifraga oppositifolia (Stenstr¨omand Molau, 1992; Gugerli, 1998).

1.2.2 Benefits for Insects Plants are not the only beneficiary in this relationship. It has been argued that the pollen would have served as an attractant to the first pollinating insects, because it pre-dates angiosperm plants. It is one of the most nutrient- rich parts of a plant, and is commonly used by bees and other insects to rear their broods (Simpson et al., 1983). However, since it is energetically expen- sive to produce, many orders of plants have evolved nectaries to serve as an alternative attractant. The nectar produced by flowers represents a major source of energy for flower-visiting insects. Kölruter was arguably the first to study its significance (and to discover that this was the source of honey) (Proctor et al., 1996), followed by (Darwin, 1862). More recently, Hock- ing (1968) compared nectar concentrations between the high and low Arctic (Churchill, NWT and Lake Hazen, NU) and found that northern flowers produce smaller quantities of high-concentration nectar. He also found that unlike more southern ecosystems, flowers compete for insect visitors rather than insects competing for nectar. Energetics also play a significant role in the plant-pollinator relationship. Heinrich (1983) writes about the role that optimal foraging plays in nectar and pollen feeding, and also how shel- ter by the flower contributes to the energy balance of pollinators. Hocking and Sharpin (1965) as well as Kevan (1975) show the corolla of heliotropic flowers such as Dryas integrifolia and Papaver radicatum act as parabolic reflectors, and suggest that added heat from this is an added attractant to pollinating insects.

1.3 High Arctic Ecosystems and Climate Change

1.3.1 The ITEX Program Global climate change has been shown to have altered air temperatures and precipitation patterns over the past twenty years (Hinzman et al., 2005; Alexeev et al., 2012), and is predicted to have even larger eﬀects on mean temperatures in Arctic regions over the next twenty years (Hassol, 2004; Stocker et al., 2013). This will have large eﬀects on the structure and function of future plant communities (Walker et al., 2006), and has already been shown to be occurring (Hudson and Henry, 2009; Hill and Henry, 2011; El- mendorf et al., 2012a). It is well known that both insects (Downes, 1964;

3 1.4. Review of Arctic Pollination and Insect Studies

Danks et al., 1994) and plants (Chapin, 1983; Jones et al., 1997; Klady et al., 2011) can dramatically change their behaviour and growth under higher temperatures. The International Tundra Experiment (ITEX) was created to monitor the changes in plant phenology, growth and reproduction across the Arctic resulting from passive warming using Open-Top Chambers (OTCs) (Marion et al., 1997; Henry and Molau, 1997). Part of the ITEX program also involves monitoring populations of larval Gynaephora groenlandica and G. rossii (Mølgaard and Morewood, 1996), but unlike the plant communities, no long term sampling scheme has been undertaken for other land-dwelling arthropods. Insects are also key indicators of environmental change (Danks, 1992), and as their populations should be expected to change with a warming Arctic, so should their interactions (both negative and positive) with Arctic plants.

1.4 Review of Arctic Pollination and Insect Studies

Table 1.1 provides a summary of some of the major works in Arctic pollination ecology to date. Below, I will brieﬂy review the most recent work, and identify knowledge gaps that this work will operate in.

1.4.1 Confounding Effects of OTCs Researchers have shown that OTCs can alter seed production in both high and low Arctic sites for Dryas octopetala (Alatalo and Totland, 1997; Welker et al., 1997). Stenströmet al. (1997) noted latitudinal differences in the effect of experimental warming on seed set in Saxifraga oppositifolia, and suggest that warming by OTCs may reduce pollinator activity. Jones et al. (1997) also note that reduced seed set in OTC-warmed Salix arctica may be due to either reduced wind or insect pollination. However, the confounding effects of the OTCs on seed set are not well understood, and the confounding effect may alter predictions made for seed production in flowering plants in a warming High Arctic. To quantify changes, observed pollination rates within the OTCs should be compared with control plots, but rates of background pollination are not well known across high Arctic plants. Bocher (1996) suggested that understanding this was necessary for the ITEX experiment to understand the degree of wind pollination and insect pollination that occurs within the OTCs. It has not been demonstrated that OTCs directly create a pollina-

4 1.4. Review of Arctic Pollination and Insect Studies

Table 1.1: Summaries of some key studies that have contributed to the modern study of Arctic pollination ecology Author Year Location Findings Y. Chernov 1963 Yugorski Found that many flowering plants depend Peninsula, on insect pollination for seed-set Russia B. Hocking 1968 Lake Hazen, Examined differences in pollination strate- Nunavut gies between low and high Arctic flowering plants; found that high Arctic pollination networks tend to be pollinator-limited L. Bliss 1971 Various Reviewed all literature on plant reproduction in tundra ecosystems; described the characteristics of plant reproductive systems P. Kevan 1972 Lake Hazen, Examined dependence on pollination in 13 Nunavut Arctic flower plants; identified pollination deficits present as well as dependence on insect pollination in 5 species H. Elberling & 1999 Latnajaurje, Examined the composition of an Arctic J. Olesen Sweden pollinating community; identified the pre- dominance of Diptera as pollinators R. Ring 2001 Alexandra Examined abundance of insects inside and Fiord, outside of OTCs in the context with the Nunavut ITEX program; found differences in abundance in some insect families R. Lundgren & 2005 Uummannaq, Conducted a network study on an Arctic J. Olesen Greenland pollinating community; found that insect and plant species were very closely linked

5 1.4. Review of Arctic Pollination and Insect Studies tion deficit, but it is implied any pollination deficit created is due to altering flowering phenology in relation to emergence of pollinating insects (Alatalo and Totland, 1997). Bliss (1958) showed historical rates of seed germination within Arctic plants, and other authors have shown that OTCs can change seed germination rates (Wookey et al., 1995; Klady et al., 2011). The mechanism for this is not understood, but has been suggested to be a combination of temperature alteration and changes in pollination rates.

1.4.2 Insect Community Composition Ring (2001) completed pit-trap surveys that indicate lower numbers of insects are trapped in OTCs than in control plots, and has shown how this varies between taxa. However, actual visitation to flowers by insect taxa is not known, so it is difficult to say whether or not all pollinating taxa are excluded from OTCs (or attracted to them). Also, the temporal scale of measurement (collections were made weekly) was not appropriate for the scale of the ecosystem, which can undergo large changes in a phenology in only a matter of days. Identifying visitors to Family (or Genus) will help to assign degrees of pollination-importance to different taxa of insects, and ultimately help to better understand rates of seed set and plant establishment within OTCs. Some of this work has already been done at the ITEX site at Alexandra Fiord, Nunavut, and indicates that Hoverflies (Order: Diptera, Family: Syrphidae) may be responsible for a majority of the pollination in the High Arctic (Robinson, 2011), which was also observed by both Hocking (1968) and Kevan (1972b) at Lake Hazen Camp, Nunavut.

1.4.3 The Effects of Seasonality and Temperature Levels of seed set have been found to be higher in late-blooming alpine flowers due to higher numbers of pollinators (Kudo, 1993). Earlier snowmelts, and hence earlier flowering times, in the High Arctic may have a similar effect on seed set, but this depends on the synchrony between insect emergence and flower emergence. Besides snowmelt timing, other environmental variables such as wind speed, cloud cover, and ambient temperature can control day-to-day variation of insect visitation in alpine zones (Kudo, 1993), and operates similarly in Arctic zones (Totland, 1994; Bergman et al., 1996). Typically, pollinating insects minimize their energy consumption by only visiting under energetically favourable conditions (Heinrich, 1975, 1983), which is usually visible in a diurnal cycle in mid-latitude ecosystems, but may not exist in the High Arctic where insects may be more opportunistic with re-

6 1.5. Conclusions gards to visitation. It has also been noted that smaller insects are more aﬀected by changes in temperature and insolation (Gilbert, 1985), and may be “released from summer limitations on feeding and growth as the High Arctic undergoes warming. Bergman et al. (1996) found that activities of bumblebees and butterﬂies were highly correlated with air temperature and incoming radiation, and that seed-set in bumblebee-pollinated plants was reduced during colder periods due to lack of visitation.

1.5 Conclusions

Other than the work of Bergman et al. (1996), almost nowhere else in the Arctic ecological literature has such a direct connection been made between weather, insects, and seed production in flowering plants. The shortness of the flowering season makes these connections very important for both flowering plants and theirassociated pollinators. There are few studies examining the diversity and numbers of insects during the flowering season (Ring, 2001), but few examining pollinating insects (Høye et al., 2013). Changes in pollination have been inferred in some species (Chapin, 1983; Stenström et al., 1997; Jones et al., 1997), but very few studies have explicitly deter- mined levels of pollination (Kevan, 1972b), and none have examined pollination in the context of the ITEX program. Finally, long-term changes in the plant community have been observed (Walker et al., 2006; Hudson and Henry, 2009), but only recently has the importance of their respective pollination strategies been realized (Lundgren and Olesen, 2005). Insect communities may exhibit unpredictable responses because of individualistic changes in behaviour due to rising temperatures and lengthening growing seasons (Danks, 2004), highlighting the need for research that emphasizes how insect communities have changed along with plant communities. Insect communities, in general, are poorly sampled across the Canadian Arctic, and while changes in other ecosystem components (such as sea ice and snow melt) have been documented, changes in insect populations have not been studied.

1.6 Objectives

The work I have undertaken has multiple goals. Brieﬂy: • it aims to understand how OTCs interact with rates of pollination, in order to understand how reproductive changes within OTCs represent future warmed ecosystems.

7 1.6. Objectives

• it aims to understand the specific nature of a High Arctic insect community, with reference to insect taxonomy, seasonal timing, and its structure over the flowering season. This includes ambient bowl trapping and targeted netting, which will help to gauge the importance of specific groups of flower visitors.

• it aims to provide more accurate estimates of insect availability inside and outside of OTCs, and relate those to the dominant visitors found in the surrounding community.

These goals will provide a more accurate picture of how OTCs aﬀect the ﬂying insect community, the pollination regimes of Arctic plants, and how those two factors interact in the context of global change experiments.

8 Chapter 2

Pollen Limitation in Open-Top Chambers

2.1 Introduction

During the past decades, northern residents and the scientific community have witnessed large changes in Arctic plant communities (Hinzman et al., 2005; Elmendorf et al., 2012a). They have seen expansion into previously unoccupied areas (Tape et al., 2006; Morton et al., 2012), as well as changes in dominance and abundance within monitored communities (Elmendorf et al., 2012a). Climate change is predicted to bring greater changes to Arc- tic regions compared to mid-latitude regions, with mean air temperatures increasing 7-9◦ C by 2100, along with an increase in rainfall (Stocker et al., 2013). Many of these changes are already occurring (Graversen et al., 2008; Serreze et al., 2009; Alexeev et al., 2012). Plant community responses to climate change in the Arctic are not well understood, and vary highly depending on the region (Elmendorf et al., 2012b; Brochmann et al., 2013). Arctic plant communities can influence feedbacks to climate change (Wookey et al., 2009), such as CO2 flux from the soil (Oechel et al., 2000; Lund et al., 2012) and the near-surface radiation budget (Blok et al., 2010; Myers-Smith et al., 2011). Climate change in the High Arctic is predicted to be even more severe (Hassol, 2004; Stocker et al., 2013). Because of their isolation, sparse plant cover, and short growing season (8-12 weeks), High Arctic plant communities are studied far less than other ecosystems, and represent an area of large future changes and great uncertainty. For example, early snowmelt may result in an increased length of growing season, but only if mid-season droughts are offset by rain. Since its inception in 1990, members of the International Tundra Ex- periment (ITEX) have studied the effects of climate warming on Arctic and alpine plant communities. The main experimental technique used by the ITEX is open-top chambers (OTC), which rely on a passive heating ef-

9 2.1. Introduction fect by trapping incoming solar radiation and limiting convective heat loss (Marion et al., 1997; Hollister and Webber, 2000). OTCs increase the near- surface temperature over the snow-free season, and have been shown to drive changes in plant communities over a wide range of latitudes (Walker et al., 1999; Klanderud and Totland, 2005; Walker et al., 2006; Hudson and Henry, 2010; Klady et al., 2011). OTCs have also been shown to change the reproductive effort (flower numbers, seed numbers per flower) of Arctic plants (Stenströmet al., 1997; Klady et al., 2011). These changes have usually been attributed to the effect of increased air temperature, but some authors have empirically found that OTCs decrease natural insect and wind pollination (Molau and Shaver, 1997; Stenströmet al., 1997; Hollister and Webber, 2000). Asexual reproduction plays a major role in the maintenance of Arctic plant communities (Billings and Mooney, 1968; Bell and Bliss, 1980), but dispersal into unvegetated areas is accomplished by sexual reproduction and seed dispersal. As glaciers recede due to prolonged warming, the process by which plants make and disperse their seeds is important to understand (Stenströmet al., 1997; Bjorkman et al., 2013). Most Arctic plants have fairly robust pollination systems and are capable of producing at least some viable seeds by self-pollination. However, most of these plants increase seed- set when hand-pollinated or exposed to insect visitors, indicating that insect pollination is beneficial to plants (Stenströmand Molau, 1992; Molau, 1993; Totland and Eide, 1999). The relative importance of wind, insect, and self- pollination in sexual reproduction are not well studied in the High Arctic. In light of this, it is important to understand how pollination influences seed production and viability in Arctic plants, and hence, their ability to colonize new areas. The understanding of the mechanisms behind Arctic plant reproduction is at this point, mainly speculative. There are relatively few studies in- vestigating the flower and seed production of Arctic plants under different pollination regimes, and even fewer examining how these regimes interact with warming. There are equally few studies examining how OTC warming and pollination interact with seed viability. Most studies use passive methods such as seed size, but few conduct actual germination trials because of the tedious nature of the experiment. To make accurate predictions about the state of plant reproduction and spread, it is necessary to quantify how the effect of warming interacts with any induced changes in the pollination regime. In this study, I investigate how pollination changes interact with OTC warming in three Arctic flowering plant species.

10 2.2. Methods

2.2 Methods

2.2.1 Site Description The study was conducted at Alexandra Fiord, Ellesmere Island, Nunavut, in the Canadian High Arctic (Map in Figure 2.1). Alexandra Fiord is described as an “oasis in a polar desert” (Svoboda and Freedman, 1994a), and there are ITEX experimental sites located at seven distinct community types within the valley (Svoboda and Freedman, 1994b). For this study, I used the Xeric Shrub site, which is characterized by early snowmelt, peaty and sandy soils, and a deep active layer(Muc et al., 1989; Svoboda and Freedman, 1994a; Jones et al., 1997, 1999). Salix arctica is the most dominant plant at the site, followed by graminoids such as Poa arctica and Festuca brachyphylla.

2.2.2 Plant Species Arctic Willow (Salix arctica (Pall)) is a woody, prostrate shrub present in the circumpolar tundra, and can be found across a large range of latitudes and ecological conditions (Dawson and Bliss, 1989b; Jones et al., 1997). Individual plants are dioecious and can exhibit differing growth patterns between sexes (Dawson and Bliss, 1989a; Jones et al., 1999). Inflorescences are dull red vertical catkins, with nectaries present on both male and female catkins. Catkins can have hundreds of individual flowers, and because flowers can produce multiple seeds a single female catkin can produce well over 500 seeds (this work). In the High Arctic S. arctica set their next year’s flower buds at the end of the snow-free season (late July-August), and bud break commences a few days after snow melt the following year. Along with Saxifraga oppositifolia, they are some of the earliest flowering plants at Alexandra Fiord (Kevan, 1990). Warming has been shown to advance their flowering phenology and their seed development (Jones, 1995; Jones et al., 1999). Both male and female plants produce nectar, and male plants also produce copious amounts of bright yellow pollen. The pollination strategies of other species in the genus Salix tend to be a mixture between wind and insect pollination (ambophily) (Tamura and Kudo, 2000; Totland and Sottocornola, 2001; Culley et al., 2002). Salix arctica is able to be wind-pollinated, but requires insect visitation for full seed-set (Kevan, 1972b; Peeters and Totland, 1999). Mountain Avens (Dryas integrifolia (Vahl)) is a semi-evergreen dwarf shrub forming prostrate cushions, present in northern North America and Greenland (Porsild and Cody, 1980). It is closely related to its widespread sister species, Dryas octopetala, and there is some evidence of hybridization

11 2.2. Methods between the two species (Philipp and Siegismund, 2003). Like S. arctica, it produces flower buds during the autumn of the previous flowering season, but bud burst occurs later than S. arctica (Philipp et al., 1990). It produces white, 8-11 petalled perfect (bisexual) flowers with deep nectaries. Small proportions of male-only or female-only (unisexual) flowers have been noted by some workers (Molau and Mølgaard, 1996; Wada and Kanda, 2000). Some of the recorded unisexual flowers may be also due to flower herbivory by noctuid caterpillars such as Sympistis nigrita (Greg Henry, pers. comm.). The flowers are often visited by insects, and (Kevan, 1972b) has shown it to be dependent on insect pollination for full seed set. The flowers of D. integrifolia are heliotropic, and temperatures can be elevated in the flower corolla by 6-8◦C, which can benefit both reproductive development within the flower as well as insects that bask or feed within the corolla (Hocking and Sharpin, 1965; Kevan, 1975; Krannitz, 1996). I used hand-held thermo- couples to test temperature differences. Arctic Poppy (Papaver radicatum (L.)) is an annual flowering forb, present across the circumpolar tundra and alpine zones. It produces yellow, cup- shaped perfect flowers in which the female parts are fused into a capsule which swells after fertilization. Warming has been shown to increase both plant biomass and flower production in P. radicatum, as well as acceler- ate flowering phenology (Lévesque et al., 1997; Mølgaard and Christensen, 1997). These changes are thought to be caused by an increased length of growing season rather than elevated temperature (Mølgaard and Chris- tensen, 1997). Kevan (1975) found that air temperatures within the corolla could be elevated by approximately 7◦C compared to ambient temperatures, but I found that temperatures were elevated by an average to 5◦C.

2.2.3 Experimental Design To test how OTCs interact with pollination, I manipulated pollen levels inside and outside of OTCs using the three aforementioned plant species. Treatment factors included Warming (2 levels: Warmed, Control) and Pol- lination (4 levels: Hand-pollinated, Net Excluder, Cloth Excluder, Control; explained below), with 10 replicates within each combination of factors. I tagged individual plants in both OTC and Control treatments, then randomly assigned Pollination treatment to them. The population size of flowering plants within OTCs at the Xeric Shrub site was limited, I could not conduct a 4-by-2 complete cross with sufficient replication, so I removed some levels of the experiment (Table 2.1). Because finding sufficient flowering plants outside of OTCs was not an issue, I was able to use all 4 levels of

12 2.2. Methods pollination (Hand pollinated, Net Excluder, Cloth Excluder, Control) outside the Warming treatments. The final structure of the experimental design is shown in Table 2.1. Hand-pollination was conducted by taking pollen from the anthers of the same species of flowering plants using a small, soft paintbrush and transfer- ring it to the receptive pistils of fully emerged flowers on treatment plants. I made an attempt to use pollen from plants both within and outside of OTCs randomly where possible, but this was sometimes limited because of advanced flowering phenology within OTCs or site characteristics. Net Excluders were used to exclude pollinators from individual flowers, using a 1mm nylon mesh attached using thin twist-ties. This mesh was intended to exclude pollinators without causing large changes to any wind-borne pollen load. Cloth Excluders were used to gauge the importance of self-pollination, using bags of 10µm cloth to exclude any wind-borne pollen from D. integrifolia and P. radicatum flowers. All Excluder bags were attached before the flowers were receptive to pollen, and removed once the flowers had senesced and were dispersing seeds. Cloth Excluders were not used on S. arctica because the species is dioecious and cannot be self-fertilized. Rain may have created some problems later in the season by washing pollen from late-season flowers (mainly P. radicatum), but this was confined to only a few days in late July to early August when most flowers were beyond pollen receptivity and had begun to senesce. OTCs are hexagonal, plexiglass chambers approximately 1.5m across, designed to contain a 1-m2 plot, and have been found to raise the ambient air temperature by 1-3◦C. Molau and Mølgaard (1996) and Jones (1995) describe the use of OTCs used by the ITEX group, including construction and design of the chambers, and the efficacy of OTCs has been evaluated by Marion et al. (1997). In general, OTCs increase the near-surface air temperature during sunny days, and cause the date of snowmelt to advance. Hollister and Webber (2000) found that OTCs mimic an above-average warm summer, and during the summer of 2012, I found that the temperature was elevated by 1.79◦C within the OTCs. During the summer of 2012, the temperature was elevated by 1.79◦C. Ten OTC/control plot pairs were randomly assigned in 1992 when the treatments began, and four extra pairs were later added for monitoring CO2 flux from the tundra. To control for plant size, I sampled random plants from the site, collected size metrics (described in Equation 2.1,2.2 and 2.3), dried and weighed the sampled plants, and developed regression models to estimate above-ground biomass (AGB). Size metrics measured include: length of longest branch, width of largest leaf, mat length and width, rosette length and width.

13 2.2. Methods

In order to apply the Excluder bags before the flowers were receptive, plants were checked and pollination treatments were applied every day during the early growing season. After the majority of flowering was underway for each species and Excluder bags were in place, the plants were checked and pollinated using a paintbrush every 2 days. Once flowers had senesced and had begun to disperse their seeds, the entire floral head was collected and stored in individual envelopes. Some of the flowers failed to produce seeds, either due to flower abortion or being damaged by caterpillars. In some cases, I was able to see insect frass or the actual larvae, but this was not always the case. Upon return from the field site in late August, seeds were stored in a freezer at -4◦ C for 27 weeks (September-March). Batches of seeds were weighed to the nearest 0.001g, counted, and a random sample from each flowering head was taken for germination, as numbers permitted (up to 100 seeds for S. arctica, 50 for D. integrifolia and P. radicatum). Germination trials took place in a greenhouse which provided 20 hours of light daily, and maintained temperatures from 15-25◦ C. Seeds were placed on filter paper in 10 cm petri dishes and kept moist with distilled water. Seeds were checked every 2 days from May 15 - June 14, 2013, and germinated seeds were removed from each dish and counted. I defined “germinated” as showing exposed cotyledons (S. arctica) or an exposed rootlet of >5mm (D. integrifolia and P. radicatum).

2.2.4 Statistical Analyses To compare numbers of flowers produced per plant, I used Generalized Lin- ear Models (GLM) with a Zero-Truncated Negative Binomial (ZTNB) distribution and a log-link function. This was necessary because the data did not fit assumptions of normality and heteroskedasticity for a traditional ANOVA model. Overdispersion in the data was too large to use a Poisson GLM, so I used a Negative Binomial GLM (Hilbe, 2011). A Zero-Truncated distribution (sometimes referred to as a “hurdle” model) was necessary because plants that failed to produce flowers could not receive pollination treatments, making it impossible for a treated plant to have zero flowers. Such models are described in Zuur et al. (2009) and Hilbe (2011). I selected the “best” model using Akaike’s Information Criteria (AIC), using second-order bias- corrected AIC to account for sample size (Burnham and Anderson, 2002; Anderson, 2008). AIC is considered a predictor of information entropy in a model, and is used to select the most parsimonious model (Anderson, 2008). To examine the AGB:flower production relationship, I used Zero-Truncated

14 2.2. Methods

Negative Binomial GLMs. I included inferred AGB as a predictor to reduce any confounding eﬀect of plant biomass on ﬂower production. All predictor metrics were included in the original model, then AIC was used to determine the “best” model. Inferred biomass was calculated as follows for each species:

log Bsalix = b0 log W + b1 log L + b2 log LB + b3 log L × log LB + (2.1)

Where B = Above-ground biomass, W = Mat Width (cm), L = Mat Length (cm), LB = Longest Branch Length (cm), and = error

log Bdryas = b0 + b1 log W + b2 log L + (2.2) Where B = Above-ground biomass, W = Mat Width (cm), L = Mat Length (cm), and = error

log Bpapaver = b0 log W + b1 log L + b2 log LW + b3 log W × log LW + (2.3)

Where B = Above-ground biomass, W = Rosette Width (cm), L = Rosette Length (cm), LW = Width of largest Leaf(cm), and = error To model the seed response across treatments, I used generalized linear mixed-effects models (GLMM), with seed response for each harvested flower nested within plant. GLMMs are relatively new in statistical literature, and are sensitive to the same assumptions that underlie both GLMs (Hilbe, 1994; Neuhaus and McCulloch, 2011) and linear mixed-effects models (LMM) (Laird and Ware, 1982; Pinheiro and Bates, 2000; Zuur et al., 2009). Bolker et al. (2009) gives an excellent overview of assumptions and fitting methods associated with GLMMs. For each model, seed response was modeled using Pollination and Warm- ing as Fixed Effects, with each individual plant as a Random Effect (necessary to avoid pseudoreplication). This structure of mixed model was repeated for the following responses:

• Seed Number

• Total Seed Mass (g)

• Average Seed Mass (Total Seed Mass/Seed Number) (g)

• % Germinability (Number Germinated/Number Sampled) x 100

15 2.3. Results

All statistical analyses were done using R 3.0.2 (R Core Team, 2013). Bi- nomial GLMs were fit using the base stats library, the zero-truncated GLMs were fit using the VGAM library (Yee, 2013), negative binomial GLMMs were fit using the glmmADMB library (Fournier et al., 2012), Gaussian, Pois- son and binomial GLMMs were fit using the lme4 library (Bates et al., 2013). The seed germination data were found to be highly overdispersed, and was modelled using a Markov-Chain Monte Carlo (MCMC) approach through the MCMCglmm library (Hadfield, 2010), which allows for overdispersion and is more robust than likelihood-based methods of parameter estimation. Wald z-tests or t-tests of significant effects (i.e. p<0.05) are not reliable for small sample sizes in GLMs and are not defined for LMMs or GLMMs. Likelihood-ratio tests are also unreliable for small sample sizes, and their performance in a GLMM context is not well studied (Pinheiro and Bates, 2000; Bolker et al., 2009). I cite differences between the nested candidate models using ∆AIC, which is a measure of model parsimony. For citations of differences between candidate models, a negative ∆AIC indicates that adding the term improves the model (Anderson, 2008). Table 2.6 contains an overview of flower response to pollination and warming.

2.3 Results

Using a handheld thermocouple probe, I found that temperatures were elevated by only 1◦C on average within the corolla of D. integrifolia. However, the temperature within the corolla of P. radicatum was elevated by an average of 5◦C.

2.3.1 Flower Response Salix arctica exhibited no response in flower number to warming treatment (∆AIC = 1.23). The effect of pollen was negligible both inside (∆AIC = 2.08, Figure 2.6.1) and outside the warming treatments (∆AIC = 2.64, Figure 2.7a). AGB was an important predictor of flower number (∆AIC = -6.22), but the model was not improved by adding warming, pollination, or any higher-order combination of the terms. Dryas integrifolia forms flower buds the previous year similar to S. arctica, but responded completely differently to warming treatment. Out- side the warming treatments, pollen did not alter flower numbers (∆AIC 2.73, Figure 2.7b). Flower number within warming treatments responded to pollen and showed an interaction between warming and pollination (∆AIC = -6.88), where plants that were warmed but unpollinated produced the

16 2.3. Results greatest number of flowers per plant (Figure 2.6b). However, when I used inferred AGB as a covariate to correct for the size of the Dryas mats, a warming term improved the model (∆AIC = -5.70), but pollination did not (∆AIC = 0.69). This can be seen in Figures 2.6e and Figure 2.8 which shows that biomass influences flower production, but only if the plant is warmed. Papaver radicatum also exhibited no response in flower number to pollination (∆AIC = 12.56) or warming (∆AIC = 1.95). AGB was found to improve AIC the most (∆AIC = -15.36), but the model was not improved any further by adding warming, pollination, or any higher-order combination of the terms. Figures 2.6 and 2.7 show that the flower numbers and flower numbers per unit AGB for P. radicatum are very similar.

2.3.2 Seed Response Salix arctica exhibited a dramatic response to pollination manipulation, increasing the number of seeds produced (∆AIC = -4.28) and total biomass of seeds (∆AIC = -1.2) when pollinated, while not increasing the overall seed size (∆AIC = 22.40). Pollinated catkins produced an average of 100 more seeds inside and 145 more seeds outside the OTCs, compared to their unpollinated counterparts (Figures 2.9a, 2.10a). OTC warming did not affect seed number (∆AIC = 2.02), nor did the interaction between warming and pollination, indicating that S. arctica may be generally subject to pollen limitation, but that this is not altered by OTCs (Figure 2.9a). Pollination and OTC warming appears to have not altered germination in any important way, but this is difficult to interpret because of the very low germinability of S. arctica seeds (Figures 2.11, 2.12). I found a marginal effect of warming, pollen, and a warming:pollen interaction on seed germination in S. arctica using a MCMC approach to model fitting (∆DIC = 1.08). However, the Deviance Information Criteria (DIC), a Bayesian analogue of AIC, showed very little difference between the full model (Warming + Pollen + Warming:Pollen) and the null model, indicating that the difference between candidate models is very small. Warming was only significant if high-order combinations of terms were included. Dryas integrifolia did not change total seed number or biomass in response to OTC warming or pollination. For seed germination, warming, pollination, and a warming:pollen interaction were identified as being important (∆DIC = -3.35). ∆DIC values between candidate models were small, but a MCMC modelling framework also identified the full model as having the best DIC score, although the interaction term was not significant (pmcmc = 0.136). Outside the OTC treatments, pollen was important in predicting

17 2.4. Discussion germinability (∆DIC = -1.84), with hand-pollinated treatments producing more viable seeds (pmcmc = 0.026). Papaver radicatum also did not change seed number or biomass with OTC warming or pollination. I found a marginal effect of warming, pollen, and a warming:pollen interaction on seed germination using a MCMC approach (∆DIC = -1.08), but the DIC differences between models was very small. This is most likely due to small number of control plants used, as well as the low overall germination values. Similar to S. arctica, this makes the results difficult to interpret, but in general there was very little effect on germinability by OTC warming (∆DIC = 3.17) or pollination (∆DIC = 0.47). Within the “best” (full) model, no terms were found to be significantly different from 0 (pmcmc >0.2). However, outside the OTC treatments, I found that the selfing treatment caused a decrease in germinability (pmcmc < 0.001), but hand pollination and insect exclusion did not. See Table 2.3 for an overview of the seed response. For detailed tables of AIC values for all candidate models, see Tables A.2, A.3, and A.4

2.4 Discussion

2.4.1 Salix arctica Neither warming nor pollination altered flower production did not change in S. arctica. This is not surprising given that S. arctica produces flower buds the previous season. Pollen addition was the main factor constraining production of seeds in S. arctica. I did not find evidence to suggest that OTCs alter seed production, or that they alter the pollination of S. arctica flowers. Jones et al. (1997) found that the ratio of seeds:flower in individual Salix catkins was decreased by OTCs, which they used to imply that pollination was reduced within the treatments. While not directly counting flower numbers per catkin, I recorded growth of the terminal shoot (length of catkin + length of stem) for each catkin, which has been shown to be a linear predictor of flower number (Jones, 1995). I found that neither warming nor pollination had any effect on the length of the terminal shoot (i.e. number of flowers per catkin), but Jones et al. (1999) has shown that this can vary from year-to- year and habitat-to-habitat. Pollen treatment did not alter the total number of catkins produced by S. arctica, because flower buds are grown at the end of the previous season. Salix arctica germination was not largely affected by either pollination

18 2.4. Discussion or OTC warming. Both inside and outside the OTCs, I found that all nested models had a very similar DIC, indicating that the effects of pollination and OTC warming are not largely important in germination. Much of this is probably due the inherently low germinability of S. arctica seeds. This also may be due to the sample size used, as well as the structure of the binomial GLMM required to analyze nested, overdispersed, binomial data. In the future, larger numbers of plants per level of treatment (>15) should be used if analyzing germination under a GLMM framework. My low recorded germination rates for Salix arctica are consistent with other studies on germination (Bliss, 1958; Billings and Mooney, 1968; Daw- son and Bliss, 1989a). However, Klady et al. (2011) tested seed germination across sites in the Alexandra Fiord Lowland, and recorded much higher germination rates for S. arctica (23%) than what were found in my study. This may have occurred for a few reasons: Klady et al. (2011) used a much shorter cold stratification period (1 month) before testing germinability, and used a longer photoperiod (24hrs). The length of stratification is more likely the cause of the difference between my treatments, because Dawson and Bliss (1989a) used a similar cold stratification period (-30◦ C. for 18-24 weeks) to ours, and reported similar overall germination (2%). Salix seeds are also very small, on the order of 0.001 g per seed. The very small amount of endosperm along with each fruit means that viability decreases very quickly over time (Densmore and Zasada, 1983).

2.4.2 Dryas integrifolia As a species, the reproductive responses of D. integrifolia have not been studied as much as its more widespread sister taxa D. octopetala. I found that OTC warming increased flower production per unit AGB in D. integrifolia. This is most likely caused by a decreased rate of bud abortion in warmed plants. Wookey et al. (1993) also found that artificial warming treatments can stimulate flower production in D. octopetala, despite the fact that Dryas sets reproductive buds the previous year. They attribute this to a decreased rate of flower abortion and unsuccessful bud- burst within warmed treatments. Similarly, I found that warming treatments increased the Flower Production:AGB ratio for individual plants, whereas control plants produced approximately the same number of flowers per plant regardless of the biomass. Pollination treatments did not alter this relationship. Although flower number responded to warming, I did not find any changes in seed number or seed mass resulting from OTC warming or pollination

19 2.4. Discussion treatment. In this respect, my findings differ from the results of Welker et al. (1997) who found that OTCs increased both seed number and seed mass in D. octopetala . However, their between-site findings were very different, indicating that D. octopetala has a strong dependence on local environmental conditions. I found that that germinability of D. integrifolia was affected by OTC warming, pollination, as well as their interaction. Because I also found increased germinability in hand-pollinated plants outside OTCs, it is likely that seed viability is related to both warming and pollination. Because I found lower seed viability outside of the OTCs, it is not likely that OTCs are interfering with pollination in any significant way, and that the increased viability is caused by the elevated air temperatures. My pollen treatments outside of the OTCs revealed that pollen addition increases germinability in D. integrifolia, but that exclusion of insect pollinators or wind has no large effect on germinability. Kevan (1972b) found that insect exclusion caused a reduction of seed-set in D. integrifolia, and that emasculated flowers were still capable of producing some seeds in an insect-free environment, although his sample size was small (1 plant, 5 flowers). I also found that D. integrifolia can produce seeds in the absence of pollinators. A possible explanation for this is that the flowers require small quantities of pollen relative to the amount of pollen they produce. Philipp et al. (1990) found that in D. integrifolia only 1% of the total pollen produced by a single flower was necessary to pollinate all of the stigmas on the flower. In this way, D. integrifolia can be thought of as a pollination “opportunist”: extra pollen enhances germinability, but it is not dependant on these external vectors.

2.4.3 Papaver radicatum I found that experimental warming did not increase flower production, or flower production per unit AGB in P. radicatum. AGB was also not different between control and OTC for P. radicatum. Seed number and seed mass were unaffected by either warming or pollination treatments. This indicates that the mating system of P. radicatum is fairly resistant to changes in pollination rates and ambient temperature. Kevan (1972b) found that P. radicatum exhibited no response in seed production to exclusion of pollinators, meaning that self-pollination is common in this system. At the level of the flower, the temperature effect of OTCs may be relatively small, because P. radicatum are capable of maintaining a high-temperature microclimate within their corolla by tracking the sun (Kevan, 1975).

20 2.4. Discussion

The germination response ofPapaver radicatum is difficult to analyze. Because I did not exclude insects from hand-pollinated blossoms, I cannot exclude the possibility that the action of hand-pollination either imperfectly deposited pollen or damaged the stigmas, confounding a change in overall germinability. However, I believe that my treatments were not overly unrealistic, and conclude that the pollination system of P. radicatum is robust enough to not require large amounts of cross-pollination. Given that many plants at the edge of their range retain some degree of self-pollination, this is not surprising. I exclude germination conditions as a possible factor, because Olson and Richards (1979) found that final germination rates were not largely affected by temperature conditions. Karlsson and Milberg (2007) found that the time of seed collection was an important factor in seed germination. I did not find any effect of the day of seed collection through the season, most likely due to the short range of collection days late in the season. In the control plants, germinability was reduced strongly by the selfing treatment (pmcmc <0.001), but not strongly altered by either hand- pollination or insect exclusion (pmcmc¡0.1). This is more likely due to changes in temperature caused by the selfing treatments, rather any kind of self- incompatibility mechanism. Papaver radicatum is heliotropic, and temperatures can be strongly elevated within the corolla (Hocking, 1968; Kevan, 1975). Corbett et al. (1992) found that obstruction of flower petals can cause the blossoms to not track the sun, and have lower ovary temperatures, lead- ing to smaller and fewer seeds. I suspect that this may have been the case with the selfing treatments, as the cloth required to exclude any wind-borne pollen necessarily covered the entire corolla, which probably caused a drop in temperature. While I did not find smaller seeds within the selfing treatment, it is conceivable that it may have altered germinability. The exclusion treatment (1mm net) is probably a more realistic estimate of self-fertilized seed production in P. radicatum, given that wind-pollination events are rare in Papaver. OTCs do not strongly alter the magnitude of (seed) reproductive response of P. radicatum. Other species of Papaver, such as P. somniferum, are generally insect-pollinated or self-pollinated because of their sticky, dense pollen (Patra et al., 1992; Miller et al., 2005). Papaver radicatum is similar, but has much higher rates of self-pollination than lower-latitude Papaver species (Nordal et al., 1997). Papaver radicatum can be considered to be a complex of different subspecies (Solstad et al., 1999), so it is possible that individual subspecies could have slightly different responses to temperature and pollination. Year-to-year variability was also not considered within this

21 2.5. Conclusions study, but can strongly influence both the timing and magnitude of flower production (Lévesque et al., 1997).

2.5 Conclusions

Many studies have shown that OTC warming can have variable eﬀects on sexual reproduction in Arctic and alpine plants, but I found that OTC warming and changes in pollination are generally independent. Of the three plant species I examined:

• Salix arctica altered seed production in response to pollen levels, producing more seeds when hand-pollinated, and fewer when insect visitors were excluded.

• Dryas integrifolia produced more ﬂowers per unit of AGB in OTC warming treatments, and displayed higher germinability in both warmed and pollinated treatments.

• Papaver radicatum reproductive output was not largely altered by OTC warming or pollen manipulation.

Seedling establishment is very rare in the Arctic, mainly due to low summer temperatures and low water availability for seedlings (Bell and Bliss, 1980). Establishment typically happens in climatic “windows” for long-lived species (Bliss, 1958; Eriksson and Fröborg, 1996). Almost all High Arctic plants can be thought of as stress tolerant C -selected species, sensu Grime (1977), or highly competitive K -selected species, sensu MacArthur (1967). Molau (1993) re-defined the systems of MacArthur (1967) and Grime (1977) in the context of tundra communities, which can be described in terms of their flowering phenology alone. Rather than r and K -selected, he defined “pollen-risking” and “seed-risking” strategies, which exist along a continuum of early-flowering to late-flowering, with corresponding rates of low selfing to high selfing. Examples of “pollen risking” strategists include S. arctica and Saxifraga oppositifolia, while “seed-risking” strategists include P. radicatum With Papaver radicatum, a conflicting pattern emerges: a mid-season flowering plant that is apparently unaffected by selfing or pollination. This may be more of an artifact of the treatments used rather than an actual reflection of how the plants reproduce. Papaver radicatum is highly dependent on insolation to produce seeds (Corbett et al., 1992), and assumedly, to produce viable seeds. Kjellberg et al. (1982) found a similar pattern in D. octopetala. The 10µm cloths that I used to exclude wind-borne pollen

22 2.5. Conclusions from the flowers of P. radicatum would also have had a shading effect within the corolla, which may have caused temperature to be confounded with selfing. This does not appear to have had a large effect in D. integrifolia. Unfortunately, there are relatively few methods to directly test rates of self- pollination aside from genetic analysis. If rates of insect visitation were to be continuously monitored over the season, it may be possible to indirectly assess how rates of visitation influence germination for Papaver radicatum. Because of the tedious nature of germination studies, there is a lack of studies of seed germinability related to warming in the Arctic. Many studies simply use seed size as a proxy for germinability, but my results show that seed size is generally independent of germinability. Cooper et al. (2004) and Mülleret al. (2011) suggest that greenhouse germination alone is insufficient to demonstrate germinability, and that field trials are necessary to measure the actual germination probabilities. To my knowledge, there are no studies on field trials of seed germination inside OTCs in the Arctic. Even though seedling establishment is rarer in the Arctic, it is still an important factor in many Arctic ecosystems (Freedman et al., 1982; Nordal et al., 1997), and its importance will continue to increase as glaciers retreat, creating new habitats for establishment.

23 2.6. Figures and Tables

2.6 Figures and Tables

24 2.6. Figures and Tables

Figure 2.1: Location of Alexandra Fiord, Ellesmere Island (78.882◦N, 75.782◦W). Source: James Hudson.

25 2.6. Figures and Tables catkins Salix arctica (white, fluffy flowers) are dispersing seeds. Figure 2.2: The Xeric Shrub site at Alexandra Fiord, with several ITEX OTCs visible. Many

26 2.6. Figures and Tables . Plants are dioecious, with male plants maturing earlier and producing copious ♂ (Pall) Salix arctica Figure 2.3: amounts of pollen. Both male and female forms produce nectar.

27 2.6. Figures and Tables (Vahl). Their flowers are mainly complete (hermaphrodidic), but some flowers are Dryas integrifolia Figure 2.4: entirely staminate or pistillate.of All nectar forms of of all flowers have high deep Arctic nectaries, flowers and (Hocking, produce 1968). some The of flowers the are largest moderately volumes heliotropic.

28 2.6. Figures and Tables spp. (Diptera: Muscidae) Phaonia (L.) All Papaveraceae lack nectaries, but produce large amounts of sticky, dense Papaver radicatum Figure 2.5: pollen. Their flowers are highlyhigher heliotropic, and than the the temperature surrounding within the air. bowl-shaped corolla The can fly be basking significantly in the corolla is a male

29 2.6. Figures and Tables P. , b) , and f) S. arctica D.integrifolia , e) S. arctica 2 between candidate models. > . Flowers per gram AGB shown for d) indicates ∆AIC P. radicatum a, b , and c) . Letters Figure 2.6: FlowerD.integrifolia output fromradicatum hand-pollinated and warmed plants. Flowers per plant for a)

30 2.6. Figures and Tables , e) S. arctica indicates indicates a . Flowers per gram AGB shown for d) P. radicatum , and c) . Pollination treatments are described in Methods. Letter D.integrifolia , b) P. radicatum S. arctica , and f) 0 between candidate models. ≈ Figure 2.7: Flowershown output for from a) pollen-manipulatedD.integrifolia plants outside warming treatments. Flowers per plant are ∆AIC

31 2.6. Figures and Tables

Figure 2.8: Flower output from warmed and control D. integrifolia plants as a function of above-ground biomass (AGB). All measurements are per plant.

32 2.6. Figures and Tables , S. arctica 2 between candidate models. > . Mass of seeds per flower is shown for d) indicates ∆AIC P. radicatum a, b , and c) . Letters D.integrifolia P. radicatum , b) , and f) S. arctica D.integrifolia Figure 2.9: Seeds pershown flower and for seed a) mass pere) flower from hand-pollinated and warmed plants. Seeds per flower is

33 2.6. Figures and Tables 2 between candidate models. > . Flowers per gram AGB shown P. radicatum indicates ∆AIC a, b , and c) . Letters D.integrifolia , b) P. radicatum S. arctica , and f) D.integrifolia , e) S. arctica Figure 2.10: Seeds per ﬂowerFlowers and per seed plant mass are per shown ﬂower fromfor for pollen-manipulated d) a) plants outside warming treatments.

34 2.6. Figures and Tables , e) S. arctica 2 between candidate models. > . Seed germinability is shown for d) P. radicatum indicates ∆AIC a, b , and c) . Letters D.integrifolia , b) P. radicatum S. arctica , and f) Figure 2.11: Average seedis mass shown for and a) germinabilityD.integrifolia from hand-pollinated and warmed plants. Average seed mass

35 2.6. Figures and Tables 2 between candidate > . Seed germinability is P. radicatum indicates ∆AIC a, b , and c) . Letters D.integrifolia , b) P. radicatum S. arctica , and f) D.integrifolia , e) S. arctica models. shown for d) Figure 2.12: Averagements. seed Average mass seed and mass germinability is from shown for from a) pollen-manipulated plants outside warming treat-

36 2.6. Figures and Tables

Table 2.1: Factors used in final design of experiment. A complete cross between Warming and Pollination was not possible due to the small number of plants available within the Warmed (OTC) treatments. Pollination treatments: Control plants were not altered. Pollinated plants were hand- pollinated. Excluded plants had 1mm mesh net Excluder bags placed over flowers to exclude pollinators. Selfed plants had 10µm cloth Excluder bags placed over flowers to exclude all external pollen. Selfing treatments were not applied to S. arctica because the plants are dioecious. Salix arctica Pollination Control Pollinated Excluded Selfed Total Control 10 Plants 10 Plants 10 Plants - 30 Warming OTC 10 Plants 10 Plants - - 20 Total 20 20 10 0 50

Dryas integrifolia Pollination Control Pollinated Excluded Selfed Total Control 10 Plants 10 Plants 10 Plants 10 Plants 40 Warming OTC 10 Plants 10 Plants - - 20 Total 20 20 10 10 60

Papaver radicatum Pollination Control Pollinated Excluded Selfed Total Control 10 Plants 10 Plants 10 Plants 10 Plants 40 Warming OTC 10 Plants 10 Plants - - 20 Total 20 20 10 10 60

37 2.6. Figures and Tables

Table 2.2: Models explaining flower number in response to warming and pollen manipulation. - indicates no important effect by any treatment factors. For specific AIC values, see Table A.2. F lower# Treatment Flower# Biomass Salix -- OTC∗pollen Salix pollen -- Dryas Warming +Pollen Warming OTC∗pollen +Warming:Pollen Dryas pollen -- Papaver -- OTC∗pollen Papaver pollen --

Table 2.3: Models explaining seed number, mass, and germination in response to warming and pollen manipulation. - indicates no important effect by any treatment factors, while subscripted text indicates marginal effect (∆AIC<2). For specific AIC values, see Table A.3 and A.4. Treatment Seed# Total Mass per Proportion Seed Seed Germination Mass Salix Pollen P ollen -- OTC∗pollen Salix pollen Pollen Pollen - Pollen Dryas --- W arming+P ollen OTC∗pollen +P ollen:W arming Dryas pollen --- P ollen Papaver ---- OTC∗pollen Papaver - - - Pollen pollen

38 Chapter 3

Eﬀects of Open-Top Chambers on Flowering Patterns and Potential Insect Visitation

3.1 Introduction

Insects are key components of nearly all terrestrial ecosystems worldwide, acting as consumers, predators, parasites, and decomposers (Price, 1997; Schowalter, 2006), and their activities are well-known to contribute to ecosystem function (Holling, 1973; Losey and Vaughan, 2006). Arctic insects are no less important (Strathdee and Bale, 1998), and act as consumers (More- wood and Ring, 1998), decomposers, predators (Oliver, 1963), parasitoids (Kukal and Kevan, 1987), and pollinators (Kevan, 1972b). Some authors indicate that the importance of insects in Arctic ecosystems is understated (Roslin et al., 2013; Gillespie et al., 2013). Insects represent the bulk of the total animal diversity of the Arctic (Chernov, 1995), but in general are not well studied. As climate change increases air temperature and advances summer snow and ice melt in the Arctic, the structure and function of most ecosystems will be altered. This will be seen in a variety of ways, including increased net ecosystem production (Welker et al., 2000; Oberbauer et al., 2007; Lund et al., 2012), nutrient cycling (Epstein et al., 2000), changes in plant biomass (Hill and Henry, 2011), and timing of reproductive events (Wookey et al., 1993; Oberbauer et al., 2013). Animals will alter the timing of their reproduction, migration, and hibernation, notable examples being birds (Gas- ton et al., 2005), ungulates (Post and Forchhammer, 2008), and insects (Franz´enand Ockinger,¨ 2012).Niche-based models of range expansion are likely insuﬃcient to represent actual transition, and experimental methods are necessary to predict responses to climate change (MacDonald, 2010;

39 3.1. Introduction

Van der Putten et al., 2010). Warming experiments such as those done by researchers involved in the International Tundra Experiment (ITEX) are an attempt to study the effect of climate change on plant communities, mainly using open-top chambers (OTCs). While these methods are generally sufficient to represent climate change scenarios in plant communities (Marion et al., 1997; Hollister and Webber, 2000), their effects on animals, specifically insects, are not well-quantified. Some authors have found that OTCs change the activity of soil and plant-dwelling insects (Ring, 2001; Dollery et al., 2006; Gillespie et al., 2013). It is generally assumed that the greater air temperatures within OTCs accelerates the growth and reproduction of these insects, given that the activities of insects are highly dependent on temperature (Danks et al., 1994; Danks, 2004). However, Moise and Henry (2010) suggest that plot-based manipulations are unrealistic for estimating animal effects within global change experiments, and others have implicated that OTCs exclude pollinating insects from plants during crucial parts of their flowering period (Jones et al., 1997; Stenströmet al., 1997). The detailed composition of plant-pollinator networks in the Arctic is not well known, except for a few studies (Mosquin and Martin, 1967; Ke- van, 1972b; Olesen et al., 2008; Franzénand Ockinger,¨ 2012). Changes to the network over the growing season are often unstudied, as the continuous monitoring of flowering plants and insects is tedious work. Most studies focus only on a single species of plant (Philipp et al., 1990, 1996; Sten- strömet al., 1997) or a single group of visiting insects (Kevan and Kevan, 1970; Richards, 1973; Pont, 1993). There are very few studies examining how climate change has altered plant-pollinator networks, and even fewer in the Arctic (Franzénand Ockinger,¨ 2012; Høye et al., 2013). Dipterans (true flies) are often the dominant pollinator in Arctic plants (Mosquin and Martin, 1967; Elberling and Olesen, 1999; Robinson, 2011), but bumblebees (Bombus spp.) are often cited as being important pollinators (Richards, 1973; Lundberg and Ranta, 1980), as they can withstand fluctuations in air temperature, wind, and precipitation more readily. Furthermore, there have been no studies other than Ring (2001) that attempt to systematically quantify the effect of OTCs on ambient insect populations. In this study I quantify the structure of a High Arctic plant-pollinator network, and examine the evolution of the interactions over the growing season. In particular, I examine how OTCs alter both the level of available flowers and the levels of available visiting insects over the course of the growing season. I discuss how well these OTC-induced changes may represent future ecological interactions, particularly plant-pollinator interactions. Fi- nally, I examine the plant-visitor interaction rates, and show how differences

40 3.2. Methods in resource availability between Arctic ﬂowers can change the magnitude of interaction.

3.2 Methods

3.2.1 Flowering Community The site and location are described in Chapter 2. The flowering plant community (non-graminoid) is composed primarily of Salix arctica, Dryas integrifolia, Stellaria longipes and Papaver radicatum, with a small number of Draba lactea, Saxifraga oppositifolia, Saxifraga cernua, Saxifraga tricuspidata, Cassiope tetragona, and Pedicularis capitata individuals. Salix arctica, D. integrifolia, and P. radicatum are described in Chapter 2. Stellaria longipes Goldie subsp. longipes is a long-lived perennial that grows in a variety of habitats, and is a successful colonizer (Chinnappa et al., 2005). In primary successional sequences in the Arctic, S. longipes is often one of the first colonizers, along with Salix arctica and Saxifraga oppositifolia (Breen and Lévesque, 2006), but is also present in undisturbed communities. Flowers are small, 10-petaled, 5-7mm white flowers (Figure 3.1), and plants can be gynodioecious (female-only as well as bisexual flowers). Often their ratio of bisexual to female-only flowers changes from year-to- year or within the flowering season, depending on environmental conditions (Philipp, 1980). They are phenotypically very plastic, and can adapt to a large variety of environmental conditions due to their polyploidy and large genotypic variability (Dang and Chinnappa, 2007). To gauge flower availability to insect visitors, I monitored flowers in plots over the growing season (14 Control, 14 OTC plots), counting all open blossoms with non-withered anthers and stigmas, where the petals had not yet begun to wither. This was done in both control and OTC plots, on the same days that insect sampling was conducted. Any receptive, open, non-graminoid flower was counted. Individual catkins of Salix arctica were counted as a single blossom.

3.2.2 Insect Community To sample the overall ﬂying insect community, I followed the CANPOLIN (2009) bowl trap protocol using sets of white, yellow, and blue bowls. These 15 cm plastic bowls were attached to the ground using metal tent pegs. Tent pegs were necessary because wind storms of up to 80 km/h occasionally occur in the valley. For the 15 treatment bowl traps, a single bowl was

41 3.2. Methods placed in each of the 14 OTCs (one of the OTCs contained 2 bowls), the colour of the bowl being systematically assigned along the length of the site. For the control bowl traps, 5 of each colour was placed outside the OTCs in a 140 m transect along the site, where bowl colour was repeated systematically along the transect. This sampling procedure took place at the xeric shrub community described in Muc et al. (1989) and Svoboda and Freedman (1994a). I conducted insect sampling every two days, reducing this to three days during the latter part of the season when insect activity was visibly decreased, and no receptive flowers were available. The bowls were filled with (unscented) soapy water during the morning of the sampling days. The morning following the sampling day, the contents of the bowls were poured through a 0.5 mm mesh strainer to catch arthropods present in the bowls. Mites and Collembola may have escaped through this size of mesh, but these were not the focus of my study. Bowl traps do not give any information about taxa of insects that visit flowers, so I conducted targeted netting of visiting insects along the site outside the OTCs. Field workers walked a patrol route across the site, capturing any visiting insects they saw on flowers. The length of time during the patrol was recorded, and patrols were repeated over the course of the day by different workers. Insects I failed to capture were identified as far as visually possible (usually to Family). All arthropods were stored in 70% ethyl alcohol and transported to the lab at UBC in mid-August. Insects were pinned, identified, and labeled as precisely as possible, usually to Genus (Chironomidae, Mycetophillidae, Sarcophagidae, Tachinidae, and Ichneumonidae were only identified to Fam- ily). Soft-bodied insects, minute insects, or arthropods such as spiders were not identified, as they were rarely encountered on flowers, their abundances were low, and their populations were considered to be beyond the scope of the project.

3.2.3 Statistical Analyses To test if the composition of flowers was different inside and outside of the OTCs, I used non-metric multi-dimensional scaling (NMDS) to reduce the dimensionality of my flower count data and a multivariate analysis of variance (MANOVA) to test for differences between OTC and control “flower communities”. This was done using a permutation test of Bray-Curtis sim- ilarity, which partitions variance between variables. For my analysis, I used warming treatment and day of year as factors. Because there were many plots that had no flowers and NMDS techniques are ill-suited for dealing

42 3.2. Methods with “empty communities”, flower density for OTC and control was taken as an average of the 14 warmed and control plots. Days where no flowers were recorded in any plots were not used. To test whether OTCs influence overall flower density at the plot scale, I used Generalized Estimating Equations (GEE). GEEs are described in Liang and Zeger (1986) and Hardin and Hilbe (2003), and are essentially a version of Generalized Linear Models (GLM) that allow for more elaborate correlation structures, such as between subject or between measurement period. In this case I used Plot as a grouping structure, and used an auto- regressive model of order 1 (AR-1) to model correlation between the same plot on different days. Tests for day of maximum flowering were done in the following man- ner: the days of peak flowering for all non-zero plots were tallied, then a Student’s T-test of equal means was used to compare between warmed and control days. If the data did not meet the assumptions of a T-test, a non- parametric Kruskal-Wallis test of parameter equal distribution was used. I tested induced changes in day of first flower, the day of last flower, and the length of the flowering season (Day of Last Flower − Day of First Flower). If the day of first flower for a plot was on first day of observations, that plot was not used, and similarly if the day of last flower was on the last day of observations, that plot was also not used. Similar to the examination of the flower community, I used MANOVA to test changes in insect catches between OTC and Control plots. All community analyses were done at the taxonomic level of Family, because this was the common level to which I was able to identify all specimens. I used counts of bowl-trapped insects as the “community” data, and compared change in catches from OTC and Control plots, between bowl colours, and across the length of the season. To examine the effect of OTCs on bowl-trap catches within a single family, I also used GEEs, with an AR-1 structure to model correlation between catch rates on different days. Even though patterns of preference appear clear in terms of catch rates, these catch rates may be conflated by flower and insect abundance. In other words, if there were a higher number of receptive flowers available, or a larger number of insects present on that day, I would expect a higher catch rate. This can also be viewed in light of MacArthur’s “principle of equal opportunity”, where limited resources are used in proportion to their abundance (MacArthur, 1972). In order to examine the preference of flower visitors in relation to abundance, I scaled the catch rate by insect availability to examine the interaction rate (catch rate/bowl trap catches, used as an estimate of population size) for each group of pollinators. Interaction rates are

43 3.3. Results not directly comparable between groups of pollinators because individual groups of pollinators will be differentially attracted to bowl traps, but they are roughly comparable within each group. The data met the assumptions of simple linear regression once transformed, so I modeled interaction rates using flower availability, insolation and wind speed (air temperature was found to be collinear with insolation). No Bombus polaris were caught in the bowl traps, so I could not get any general estimates of abundance throughout the season, so I used the catch rate instead of the interaction rate. I could not transform the data to meet the assumptions of a linear model, so I compared catch rates to individual variables using a Kendall rank-correlation test. I realize that interspecific competition (Hocking, 1968) or facilitation (Heg- land and Totland, 2005; Ghazoul, 2006) may occur between simultaneously flowering plants, but a network study of this nature is complex and beyond the scope of this work. GEE computations were done using the geepack library (Halekoh et al., 2006), NMDS and community analysis were done using the vegan library (Oksanen et al., 2013), rank-order tests were done using the Kendall library (McLeod, 2011), and the remainder was done in the base library in R (R Core Team, 2013).

3.3 Results

3.3.1 Flower Availability The flower community was significantly altered by OTC warming (p=0.05) and date (p=0.004), but OTC warming explained only 4.4% of the variation, while date explained 50.3%. This indicates that OTCs do alter the overall composition of the flowering communities, but not nearly as much as day- to-day changes over the season. Warming was only a significant predictor if permutation tests were constrained by day of year, indicating that while there are differences between OTC and control plots, these differences are largely not detectable at the scale of the entire growing season. Figure 3.2 shows how the flower community changes over the course of the flowering season using NDMS scores, which represents the composition of available flowers in a multi-species space. The composition follows a clockwise arc as the community progresses from Salix to Dryas to Papaver-Stellaria. Both communities generally follow the same progression, but the warmed community progresses faster. Similar to other phenological studies (Wookey et al., 1993; Alatalo and Totland, 1997; Jones et al., 1997), the timing of flower phenology was altered

44 3.3. Results by the OTC treatments. The Day of First Flower (DFF) was significantly earlier in both S. longipes (p=0.05) and P. radicatum (p=0.0007) (Table 3.1), similar to the results of Mølgaard and Christensen (1997). Based on my past observations, and the findings of Hocking (1968) and Jones et al. (1997), I suspect that the day of first flower for S. arctica would also have been significantly earlier, but I was unable to begin surveys early enough in the season to formally test this. In S. arctica (p=0.0005), and D. integrifolia (p=0.004), I found that experimental warming♀ accelerated the Day of Peak Flowering (DPF) (Table 3.1). In P. radicatum and S. arctica , I found changes in peak flowering were only marginally significant (p=0.09).♂ In S. longipes, it was not shifted at all (p=0.41), but the senescence period was reduced. In other words, senescence occurred more quickly, but at approximately the same time of the season. The Day of Last Flower (DLF) was not altered in any species except for S. arctica (p=0.0008) and D. integrifolia (p=0.0002), in which it occurred earlier. ♂ I found that the length of the flowering season of warmed plots was significantly shortened in D. integrifolia, and lengthened for S. longipes (marginally), and P. radicatum. Warmed plots had similar densities of S. arctica catkins (p=0.7, p=0.41) and D. integrifolia flowers (p=0.8) throughout the season. However, I found that warmed plots had a significantly higher flower density of S. longipes (p=0.002) and P. radicatum (p=0.02) (Figure 3.3).

3.3.2 Insect Community General The flying insect community was altered by OTC warming (p<0.001), bowl trap colour (p<0.001), and Day of Year (p<0.001). However, warming and bowl trap colour only accounted for only 3.2% and 2.8% of the variation, respectively, while day accounted for 50.4%. This indicates that while OTCs have an effect on the insect community composition, it is not very large in comparison to day-to-day variation over the growing season (see Figure 3.4a). To illustrate the seasonal trend better, I roughly divided the communities found in Control and OTC bowl traps into Early, Mid, and Late season (Figure 3.4b). In general, the insect community follows a clockwise pattern, but the variance is much more constrained during the peak of flowering (“Mid-Season”). The pattern becomes much more variable after the “Late Season”, especially in the OTC bowl traps.

45 3.3. Results

Using the bowl-trap data over the entire season, I found that OTCs tended to reduce bowl catch rates of all insect families sampled, including the dominant floral visitors (pmcmc <0.001), but not by a large amount on a per-bowl basis. However, this gives only a general sense of decreases, and does not address differences between families or genera. When I tested day-to-day bowl catch rates using a GEE, I found that OTCs significantly reduced the bowl catch rates (p<0.0001) for the five main families of insects observed, particularly for the Ichneumonidae, Noctuidae, and Syrphidae. This can be seen in Figures 3.5, 3.6, and Table 3.2, which show lower catches of all the dominant families of flying insects. In particular, Syrphidae catches were reduced by 80%. Ichneumonidae and Noctuidae were reduced by 70% and 50%, respectively. Finally, Dolichopodidae and Musidae were reduced by 25% and 20%, respectively.

Flower visitors The most dominant flower visitors were flies (Diptera) in the families Syr- phidae and Muscidae, followed by Bombus polaris (Hymenoptera: Apidae). Eupeodes curtus and Phaonia spp. were by far the most common visitors, followed by Platycheirus spp. and Drymeia spp. Bombus polaris, Melang- yna arctica, and Eupeodes nigroventris were also found in abundance (Table 3.3). In terms of hourly visitation rates, Muscidae were the dominant flower visitors during the early part of the flowering season (June to mid-July), while Syrphidae appeared more frequently during the late season (mid-July to August). Figure 3.7 displays the peaks in catch numbers graphically, and Muscidae seem to show a preference for D. integrifolia while Syrphidae seem to show a preference for P. radicatum (Table 3.4).

3.3.3 Interaction Rates Syrphidae Net catch rates (Catches/hr) of both Syrphidae and Muscidae on Dryas integrifolia were correlated with Muscid population (Kendall τ=0.24, p=0.02) and Syrphid population (Kendall τ=0.55, p<0.0001). The catch rate on all other flowering plants showed no relationship with insect population. Inter- action rates (Net Catch Rate/Bowl Catch Rate) for Syrphidae were largely unaffected by overall floral density, except for P. radicatum (p<0.0001) and Stellaria longipes (p=0.03), which showed an increase in interaction rates at higher flower densities.

46 3.4. Discussion

I also found that increased insolation tended to decrease Syrphidae interaction rates with P. radicatum (p=0.02), implying that the Syrphidae seek out blossoms of P. radicatum when insolation is lower, possibly for basking (Figure 3.9). Insolation and air temperature are correlated (r2=0.39, p<0.0001), but I found that the model involving insolation was superior to the one involving air temperature (∆AIC -4.1).

Muscidae For the Muscidae, interaction rates were unaffected by overall floral availability, and tended to show comparable interaction rates at any surrounding density of flowers. Their interaction rates were also largely unaffected by wind speed and insolation.

Bombus polaris For Bombus polaris, relatively few numbers of insects were netted in comparison to other pollinator clades (Figure 3.8). However, I found that similar to the Syrphidae, B. polaris catches on P. radicatum were positively influenced by overall flower density (p=0.02), but not by wind speed or insolation. I had too few observations to examine S. longipes visitation by B. polaris, and B. polaris was not netted on the other dominant flower species, D. integrifolia or S. arctica. Figure 3.9 shows the interaction rate for Papaver radicatum against flower density and insolation for both the Syrphidae and for Bombus polaris.

3.4 Discussion

3.4.1 Flower Availability During the summer of 2012, the OTC plots at the xeric shrub site were in their 21st year of continuous warming treatment. 2012 also represented one of the warmest years on record for the Canadian High Arctic, and also for Alexandra Fiord. Despite fairly consistent results across warmed Arctic sites (Klady, 2006; Elmendorf et al., 2012b; Oberbauer et al., 2013), interannual variability is an important component of studying Arctic ecosystems (Jones, 1995; Henry and Molau, 1997; Jones et al., 1997; Høye et al., 2007). Some authors have examined “snapshot phenology” of plots during the peak ﬂowering season (Wookey et al., 1995). Others have examined it at the plant scale over the season (Wookey et al., 1995; Stenstr¨omet al., 1997;

47 3.4. Discussion

Totland, 1999), but to my knowledge, there are no other Arctic studies that have examined flower availability at a plot scale continuously across an entire flowering season. However, several mid-latitude studies have examined flower availability at varying time scales (Holzschuh et al., 2007; Elliott, 2009). I found that OTCs altered flower availability in a variety of ways, but that generally differences between OTC and control plots were associated with the timing of flowering, and sometimes with overall density of flowers. Because we did not arrive soon enough to begin measurements of S. arctica, I could not observe changes in the day of first flower or length of season. Hocking (1968) found that male plants tended to flower earlier than female plants. Other authors have found that OTC warming did not increase the day of first mature flower in plants of either sex of S. arctica (Jones et al., 1997), but this is subject to much interannual variation. I found that the OTC warming accelerated the day of peak flowering significantly in both male and female plants, which suggests that the day of first flower may also be earlier. The day of last flower was not altered, and overall flower density (per plot) was not altered, indicating that OTC warming affects the timing of flower production, but does not influence overall flower production in S. arctica. OTC warming accelerated the phenological development of Dryas integrifolia. Other authors have reported similar results in Dryas octopetala (Wookey et al., 1993, 1995; Welker et al., 1997). My results were similar to results of the authors mentioned, in that the timing of first flower was not affected, but that advances in flowering became apparent soon after the early season. I also found that the day of last flower was advanced by six days in OTCs, and that overall flowering season was shortened by four days, indicating that visiting insects that rely on D. integrifolia may be forced to alter their diet under future scenarios. OTC warming increased the per-meter flower density of Stellaria longipes, but did not alter the timing of flower production. Stellaria longipes has never been studied in the context of OTC warming, so these can be taken as pre- liminary predictions of future S. longipes flower densities, at least at similar xeric sites. This is relevant for the pollinator community, as S. longipes appears to be an important food source for the Syrphidae. Although I did not specifically examine feeding habits, I did observe large numbers of Dipter- ans drinking nectar in the corolla of S. longipes. It produces large amounts of sweet nectar (Hocking, 1968), and Kevan (1973b) has shown that their nectar is a food source of parasitic wasps in the Arctic (Chalcididae, Bra- conidae, Ichneumonidae). To my knowledge, there is currently no literature on how S. longipes responds phenologically, structurally, or reproductively

48 3.4. Discussion to induced warming, but this is an indication that it will likely respond positively under future warmed climates. Warmed plots significantly shifted the flowering in Papaver radicatum earlier by six days on average, and showed an increased length of the overall flowering season by eight days. I also found that the overall density of Papaver radicatum flowers was increased in the warmed plots, but without measurements of plants per plot it is impossible to know whether this is from increased P. radicatum establishment, or rather increased reproductive effort. Klady et al. (2011) found that P. radicatum did not increase per- plant reproductive effort when experimentally warmed, which I also found in Chapter 2. My measurements were in flowers/m2 while Klady et al. (2011) measured flower biomass/plant, but I suspect that some of the increase in flower density during the growing season is due to greater establishment in the warmed plots.

3.4.2 Insect Community Insects and OTCs While OTCs have been found to drive changes in Arctic plant communities by passive warming (Hudson and Henry, 2010; Elmendorf et al., 2012a), these changes are not expected to be seen to the overall insect community, because any accelerated emergence or feeding patterns of insects within OTCs would be dwarfed by the greater population of “unwarmed insects” from outside the chambers. Some authors have studied the behaviour of Hemiptera and larval Lepidoptera within OTCs, but this was only possible through use of a corral which confined the insects within the OTCs , and is essentially impossible to do with flying insects. Bocher (1996), Stenström et al. (1997), and Jones et al. (1997) all recognized that passive warming experiments such as OTCs may exclude insects from plants, and I have pre- sented quantitative evidence to suggest that they were correct. Primarily this affects low-flying, medium-sized insects such as wasps and flies. I have observed flies and wasps encounter the angled plexiglass of the OTCs, right themselves after the collision, and fly away in a different direction after a short period. This appears to cause substantial reductions in catch rates, with an 80% reduction in Syrphidae catches and a 70% reduction in Ich- neumonidae catches (see Results, and Table 3.2). However, the impacts of this exclusion are not well known. Of the five dominant insect families, I will review possible confounding effects found within OTCs that may be unrepresentative of future Arctic plant communities.

49 3.4. Discussion

The reduction of Muscidae and Syrphidae is significant mainly in terms of reduction to pollination within OTCs. Both families of Diptera have been shown to be the dominant floral visitors in most Arctic regions (Ke- van, 1972b; Pont, 1993), and their reduction in availability to plants within OTCs may provide unrealistic estimates of pollination rates within future ecosystems (Alatalo and Totland, 1997). However, reduction in visitation is more likely to affect the early season pollen-risk strategists such as Saxifraga oppositifolia (Molau, 1993), as plants that flower later tend to be associated with lower rates of self-incompatibility. I report similar results in Chapter 2, which indicates that late-flowering plants such as P. radicatum are fairly robust to changes in pollination. The behaviour of other Arctic insects within warmed environments has been studied relatively little. Because Arctic insects are highly dependent upon their surrounding for thermoregulation (Danks, 1996, 2004), ground- dwelling invertebrates, particularly Arachnids, Collembola, Hemiptera, and larval Lepidoptera can be found in greater densities within OTCs (Richard- son et al., 2002; Gillespie et al., 2013). They will stay inside of OTCs when given the opportunity, and Ring (2001) has found evidence that smaller Dipterans (Nematocera, Chironomidae, Empididae) also prefer OTCs. I found that OTCs influence the composition of the insect community on a day-to-day basis. In particular, larger insects such as Muscidae, Ichneu- monidae, and Dolichopodidae are found less within OTCs. This is particularly important because Ichneumonidae and Dolichopodidae are ecologically important in many ecosystems as parasitoids and predators, respectively (Jervis and Kidd, 1986; Gelbi˘cand Olejn´ı˘cek,2011). In Arctic insect communities this is no less true. For example, at the Alexandra Fiord site, the dominant Lepidopteran grazer Gynaephora groenlandica is subjected to mortality rates of up to 95% due to Ichneumonid and Tachinid parasitoids (Kukal and Kevan, 1987). From this, I imply that OTCs likely cause artificial trophic imbalances by excluding ambient predatory or parasitic insects, while promoting the activity of smaller soil, plant, or ground-dwelling insects. Because I was primarily interested in pollinating insects within OTCs, smaller unidentified arthropods such as Nematocera, small Braconidae, and Acari (Mites) were largely overlooked for the purpose of this study, but may be highly influential on the Hemiptera (Aphids) that feed on the plants within the OTCs. Dollery et al. (2006) have shown that OTC warming increases populations of soil- dwelling mites, Chironomid larvae, and plant-feeding aphids, while reducing Hymenopteran parasitoids. While not explicitly sampling for parasitoids, Gillespie et al. (2013) also found that aphids increased dramatically in the

50 3.4. Discussion

ﬁrst years that OTCs were present, but then were reduced to normal levels in later years. They attribute this to a corresponding increase in soil-dwelling predators such as mites and spiders, but it is uncertain if ﬂying predators would increase their growth and phenology in the same way in future climate scenarios. Much of the emergence and life history of Dolichopodidae and other predatory Arctic insects is essentially unknown, and should be a topic of future study.

Flower-visiting Insects Arctic flowering plants have relatively robust pollination strategies, and can produce seeds in absence of pollinating insects (Chapter 2). I suspect that the insects are more heavily dependent on the food and energy gained from flowers. I found that the dominant visitors of flowers are overwhelmingly Diptera of the family Muscidae and Syrphidae, followed by the Bombus polaris (Hy- menoptera: Apidae). While B. polaris is well-noted as an Arctic and alpine pollinating species (Bergman et al., 1996; Philipp et al., 1996), it is relatively uncommon in terms of actual catch rates. The per-visit efficacy of B. polaris compared to the common Arctic Syrphidae and Muscidae such as Eupeodes curtus or Phaonia spp. is not known, but is assumed to be higher in B. polaris simply due to body size and foraging behaviour (Sahli and Conner, 2007). While it is generally accepted that bees are more effective pollinators than flies (Herrera, 1987), visitation by flies can provide ample pollination, provided enough visitors are available (Mesler et al., 1980; Berenbaum et al., 2007), and this appears to be the case here. Other authors have identified that flies are often an over-looked component of many pollination systems (Larson et al., 2001; Kearns, 2001; Lundgren and Olesen, 2005), and I suggest that further study should be devoted to them, especially in Arctic and alpine ecosystems that are relatively free of bee pollinators. I did not find evidence to suggest that S. arctica are dependent on insects for pollination, as I observed very low rates of visitation to female S. arctica plants. The female catkins are also capable of making seeds (albeit lower numbers) when insects are excluded from them (Chapter 2). However, insects may be more dependent on them for a source of food, as queens of Bombus polaris were observed gathering pollen from male S. arctica early in the season when no other pollen sources were available. The queens made no systematic attempt to visit female catkins, and concentrated their foraging on pollen-laden male catkins (>30 consecutive male catkins were visited, and approximately equal numbers of male/female catkins were available;

51 3.4. Discussion personal observation). By the time that Muscidae and Syrphidae emerge, S. arctica are largely senesced and non-receptive to pollen. It is possible that early-season visits are important for S. arctica (Molau, 1993), but I did not find large numbers of insects present that would facilitate pollination other than the occasional B. polaris. I observed Syrphidae and Muscidae feeding from the deep nectaries of D. integrifolia, as well as feeding directly on the pollen from stamens. These represent an important food source for insect visitors, especially because they have some of the most nutrient-rich nectar of all Arctic flowering plants (Hocking, 1968), but without detailed observations it is difficult to assess whether pollen or nectar is the main attractant for the visiting insects. Hock- ing (1968) found that within the same plant species, nectar in Arctic flowers is much more concentrated at high latitudes, and that equal quantities were present in covered and uncovered flowers at high latitudes. He used this to show that between-plant competition for pollinators is higher in Arctic plants than in mid-latitude plants (Hocking, 1968). Kevan (1973a) views nectar in Arctic flowers as more of an attractant for Lepidoptera, and Chi- ronomidae, but has noted that about 40% of the insects in the Arctic have been found imbibing nectar. Catch rates on D. integrifolia scaled with insect abundance (bowl trap catches) for the Syrphidae and Muscidae. Large numbers of Muscidae visited D. integrifolia, most likely to forage for nectar and pollen reserves, as well as for warmth. However, I found that for both catch rates and interaction rates were not related to flower abundance for D. integrifolia, implying that their resources are not critical for their insect visitors. The more likely attractant for most flower visitors is pollen and warmth. Papaver radicatum, does not produce nectar, yet I caught almost twice the number of visitors on P. radicatum than D. integrifolia. Some of this is due to timing of insect and flower emergence, but even at low densities, P. radicatum appear to be the most attractive blossom for insect visitors, especially the Syrphidae. Pollen production and availability in D. integrifolia and P. radicatum has not been quantified, but corolla temperatures of D. integrifolia are much less than P. radicatum (Kevan, 1972b, 1975). Kevan (1973a) discussed floral attraction in Arctic plants, and indicated that flower size is a key feature of insect attraction in Arctic plants because it is linked to both visual attraction and to the thermal regime within the corolla. I also found that interaction rates of P. radicatum with the Syrphidae decreased at higher rates of insolation, indicating that they likely visit the flowers at lower temperatures to gain thermal energy. This is contrary to the results of Totland (1994) who found that visitation rate was correlated with temper-

52 3.4. Discussion atures. This is likely due to climatic differences between Alexandra Fiord, Nunavut and Mount Sandalsnut, Norway. Alexandra Fiord is in the High Arctic (78.9◦ N), and diurnal insolation and temperature are more constant than southern latitudes, even during the “night time”, whereas Mt. Sandal- snut (60.4◦ N) is subject to large variation in solar radiation and temperature over the course of the day. I also found that interaction rates for Syrphidae and the catch rate for Bombus polaris tended to scale with abundance for flowers of P. radicatum, implying that they are limiting resources (sensu MacArthur (1972)) for these insects. Syrphidae are known to feed on pollen during the time of egg formation (Kevan, 1973a). Bombus polaris queens and workers forage for nectar pollen to provide for their brood, and have been shown to feed on all the flowers regarded in this study (Richards, 1973). Richards (1973) reported that the queens of B. polaris tended to visit Salix arctica and Saxifraga oppositifolia, while the workers visited Dryas integrifolia, Pedicularis capitata and Cassiope tetragona. Interaction rates for the Syrphidae with Stellaria longipes also scaled with floral abundance, implying they are also limiting resources. S. longipes is known to produce large amount of sweet-smelling nectar and pollen. However, the flowers are much smaller and shorter than the flowers of P. radicatum, making them less attractive. They also provide very little thermal benefits in comparison to P. radicatum. In this case, it is most likely that pollen (and possibly nectar) are limiting resources for the Syrphidae. One of the reasons for the lack of B. polaris visits to anything but P. radicatum at my site may have been that the composition of available flowers at other sites was more attractive to B. polaris, but this is beyond the scope of my study. Other authors have found that insolation and air temperature tended to increase visitation in other Arctic species of Bombus (Lundberg, 1980; Bergman et al., 1996), but I failed to find any trend, possibly because I focused on overall patterns rather than diurnal patterns in visitation, as well as climatic differences between study sites. Both Bergman et al. (1996) and Richards (1973) found that Bombus queens were able to forage for longer at lower temperatures, simply because of the higher internal temperatures associated with their larger body size. I did not catch any queens of B. polaris. Because of the relatively small sample size of B. polaris netted (18 total), and the lack of overall population estimates, the relationship of between overall visitation and flower density is tenuous, and merits further study.

53 3.5. Conclusion

3.5 Conclusion

Flower production at a per-plot basis was altered strongly for most flowering plant species, and has implications for the structure of future plant- pollinator interactions. I demonstrate that: • OTCs significantly change the structure of the flowering plant community on a day-to-day basis.

• The day of peak ﬂowering for Salix arctica and Dryas integrifolia tended to be earlier in the warmed plots.

• The length of the overall ﬂowering season was shorter for Dryas integrifolia and longer for Papaver radicatum in the warmed plots.

• Flower density was higher for Stellaria longipes and Papaver radicatum in the warmed plots. Insect activity was also altered within OTCs, particularly for the dominant visitors. I show that: • OTCs signiﬁcantly change the structure of the ﬂying insect community on a day-to-day basis, and likely exclude insect predators and parasites.

• Bowl-trap catches of nearly all groups of ﬂying insects were signiﬁ- cantly reduced over the growing season in the warmed plots.

• The most dominant insect visitors were Syrphidae and Musicidae, with a few Bombus polaris.

• Syrphid flies and Bombus polaris demonstrated temperature and availability- dependent visitation to Papaver radicatum. They tended to be caught at higher rates when flower density was high and temperatures were low. OTCs have been shown to strongly alter the dynamics of flowering in Arctic plants (Wookey et al., 1993; Welker et al., 1997; Mølgaard and Chris- tensen, 1997; Stenströmet al., 1997; Alatalo and Totland, 1997; Klady et al., 2011), and similarly I found that OTCs alter the timing and magnitude of flowering in Arctic plants. While this is of interest in the context of future growth and range extensions, it is also of interest in the context of future ecological interactions. Climate change is expected to result in trophic mismatches (Post and Forchhammer, 2008; Post et al., 2009), including insect

54 3.5. Conclusion outbreaks (Jepsen et al., 2008, 2011). It has been suggested that changes in insect emergence may result in plant/pollinator mismatches (Donnelly et al., 2011; Straka, 2012) and it is possible that mismatches could occur across the Arctic (Høye and Forchhammer, 2008; Hegland et al., 2009; Høye et al., 2013). However, the extent of this is not known, given that both insect and flower phenology in the Arctic tends to be related to snowmelt (Danks et al., 1994; Høye and Forchhammer, 2008; Avila-Jiménezand´ Coul- son, 2011; Oberbauer et al., 2013). Long-term records of insect emergence and phenology are lacking, especially in the Arctic, but Høye et al. (2013) have recently demonstrated that a phenological mismatch between Arctic plants and pollinators is indeed occurring, and show that the consequences are more severe for late-emerging flower visitors. Their observations do not include actual visitor observations, but are still valuable in terms of community data. I found that Papaver radicatum flowers are a limiting resource to visiting Bombus polaris and Syrphidae. Additionally, I found evidence that Syrphi- dae visit flowers for warmth, as well as pollen resources. This adds quantitative evidence to the observations of Hocking and Sharpin (1965), Kevan (1975), Totland (1996), and others (Philipp et al., 1996; Danks, 2004) who identified flower microclimate as an important insect attractant along with scent, colour, and food resources. Considering that the corollas offer insects a food-laden microclimate on par with that of an OTC, it is no wonder that they seek out these blossoms! Löve (1969), Kevan (1972a), and Mølgaard (1989) and have studied how flower colour, temperature, and heliotropism are related in P. radicatum, but have not explicitly linked their studies to insect attraction. Papaver radicatum, and other similar heliotropic cup-shaped flowers, should be further studied at additional Arctic and alpine sites to understand how selection operates on warmth and colour.

55 3.6. Figures and Tables

3.6 Figures and Tables

Figure 3.1: Stellaria longipes Goldie subsp. longipes produce 5-7mm 10- petaled bisexual white ﬂowers. They produce sweet smelling nectar and yellow pollen. The are visited by Diptera and occasionally Bombus polaris.

56 3.6. Figures and Tables

Figure 3.2: NDMS ordination of ﬂower communities over the growing season in warmed and control plots.

57 3.6. Figures and Tables

Figure 3.3: Daily ﬂower densities for a) Salix arctica male, b) Salix arctica female, c) Dryas integrifolia, d) Stellaria longipes, and e) Papaver radicatum, in both warmed and control plots. 14 warmed and 14 control plots were monitored. 3.6. Figures and Tables

Figure 3.4: NDMS ordination of insect communities showing a) changes in NMDS scores over the season in warmed and control plots, and b) grouped into early, mid and late season communities. Abundances were averaged for each day between bowl colours, and split by warming treatment. 59 3.6. Figures and Tables

Figure 3.5: Daily bowl catches of a) Muscidae, b) Ichneumonidae, c) Dolichopodidae, d) Noctuidae, and e) Syrphidae over the ﬂowering season in warmed (OTC) and control plots. 3.6. Figures and Tables Figure 3.6: Total catch of all insects over the growing season in warmed (OTC) and control plots.

61 3.6. Figures and Tables

Figure 3.7: Hourly catch rate of a) Musidae, b) Syrphidae, and c) Bombus vistors on ﬂowers of the four main plant species.

62 3.6. Figures and Tables Figure 3.8: Total net catches of insect visitors outside of OTCs over the entire ﬂowering season.

63 3.6. Figures and Tables not deﬁned). 2 uses a Kendall rank-test (r B. polaris interaction rate (Netting Catch Rate/Population Estimate) . P-value for Papaver radicatum Bombus polaris Figure 3.9: Factors inﬂuencing the for the a,b) Syrphidae and c)

64 3.6. Figures and Tables ), ). For DLF 2 m p 0.002 0.02 (flowers/ Dens. -0.97 0.80 1.51 ), last flower ( Dens DPF p 0.04 0.006 Len. n/a n/a-4.2 -0.70 0.70 ), peak flower ( p 0.0008 0.0002 DFF DLF -6.0 -1.1-6.0 0.37 n/a n/a -3.22 0.41 p 0.0008 0.0005 0.004 DPF -2.7 0.09 1.8 0.61 7.7 p 0.0007 DFF n/an/a n/a-1.7 n/a-4.8 0.18 -3.7 -5.9 0.05 -4.6 -3.7 -1.6 0.41 0.3 0.63 5.1 0.09 4.79 ) of all species are shown, as well as overall changes in density ( Len. ) ) ♂ ♀ ( ( Plant Species Salix arctica Salix arctica Dryas integrifolia Stellaria longipes Papaver radicatum Table 3.1: Results of(Student’s T tests or for Kruskal-Wallis). Changes flowerand in response season the to day length of warming, ( firstDFF, along flower DPF, ( with and p-values DLF, foran numbers earlier tests indicate date. of how many Len. significant days difference represents the the event change was in shifted, length with of negative the numbers flowering indicating season.

65 3.6. Figures and Tables

Table 3.2: Diﬀerences in average catches between Control and OTC Bowl Traps over the ﬁve most abundant insect families (all other families had overall numbers too low to test using a GEE). Numbers under Treatment are in catches per pay over the entire growing season. Treatment Group p-value Total Catches Control OTC Diptera: Muscidae 58.33 47.25 <0.0001 2188 Hymenoptera: Ichneumonidae 25.27 7.14 <0.0001 661 Diptera: Dolichopodidae 4.56 3.38 <0.0001 189 Lepidoptera: Noctuidae 5.86 2.91 <0.0001 135 Diptera: Syrphidae 2.18 0.42 <0.0001 56

Table 3.3: Abundance of netted insect species over the entire growing season. Order: Family Species Total Diptera: Syrphidae Eupeodes curtus (Hine, 1922) 180♀ ♂ 0 180 Diptera: Muscidae Phaonia spp. 37 63 100 Diptera: Syrphidae Platycheirus spp. 34 0 34 Diptera: Muscidae Drymeia spp. 27 5 32 Hymenoptera: Apidae Bombus polaris Curtis, 1835 19 0 19 Diptera: Syrphidae Melangyna arctica (Zetterstedt, 1838) 12 0 12 Diptera: Syrphidae Eupeodes nigroventris (Fluke, 1933) 11 0 11 Diptera: Empididae Rhamphomyia spp. 3 1 4 Diptera: Culicidae Aedes spp. 1 2 3 Diptera: Syrphidae Eupeodes lapponicus (Zetterstedt, 1838) 3 0 3

66 3.6. Figures and Tables

Table 3.4: All ﬂower-insect interactions observed throughout the ﬂowering season, ranked by frequency. Flowering Plant ♂ ♀

Insect Visitor Papaver radicatum Dryas integrifolia Stellaria longipes Salix arctica Salix arctica Saxifraga tricuspidata Cerastium alpinum Draba lactea Saxifraga nivalis Total Eupeodes curtus 126 11 35 1 2 3 2 0 0 180 Phaonia spp. 25 72 0 1 1 0 1 0 0 100 Platycheirus spp. 27 6 0 0 0 0 0 1 0 34 Drymeia spp. 23 9 0 0 0 0 0 0 0 32 Melangyna arctica 11 0 0 0 1 0 0 0 0 12 Eupeodes nigroventris 8 0 2 0 0 0 0 0 1 11 Rhamphomyia spp. 1 3 0 0 0 0 0 0 0 4 Eupeodes lapponicus 3 0 0 0 0 0 0 0 0 3 Aedes spp. 0 2 0 0 1 0 0 0 0 3 Diptera Dolichopus spp. 1 0 0 0 0 0 0 0 0 1 Helophilus groenlandicus 1 0 0 0 0 0 0 0 0 1 Helophilus lapponicus 1 0 0 0 0 0 0 0 0 1 Platycheirus groenlandicus 0 0 0 1 0 0 0 0 0 1 Mycetophilidae 1 0 0 0 0 0 0 0 0 1 Scathophagidae 0 0 0 1 0 0 0 0 0 1 Chironomidae 0 0 0 1 0 0 0 0 0 1 Bombus polaris 17 0 1 0 0 0 0 0 0 18 Ichneumonidae 0 1 0 0 0 0 0 0 0 1 Hym. Psychophora sabini 0 2 0 0 0 0 0 0 0 2 Agriades glandon 0 0 0 1 0 0 0 0 0 1 Lycaena phlaeas 0 1 0 0 0 0 0 0 0 1 Sympistis nigrita 0 1 0 0 0 0 0 0 0 1

Lepidoptera Boloria chariclea 0 1 0 0 0 0 0 0 0 1 Total 245 109 38 6 5 3 3 1 1 411

67 Chapter 4

Conclusions

Experimental studies on flower pollination in the High Arctic are rare (Ke- van, 1972b), and very few of them deal explicitly with the topic of warming and pollination changes (Stenströmand Molau, 1992). In this study, I experimentally altered pollination of flowering plants, and demonstrated that any pollination deficits induced by open-top chambers (OTCs) are likely to be insignificant in an Arctic ecosystem. Salix arctica demonstrated increased seed production with hand-pollination, and decreased seed production when insects were excluded, but OTCs do not appear to alter this in any significant way. Warming and pollination did not alter S. arctica germination rates significantly. Dryas integrifolia altered its flower production under warmed conditions, producing more flowers/g of above-ground biomass (AGB) when warmed. I also found that germination rates of D. integrifolia increased when pollinated outside of the warming treatments, or when warmed by an OTC, but that pollination and warming effects are not additive. Papaver radicatum proved resilient to changes in pollination and OTC warming, and did not alter its flower production, seed production, or germination rates in response to any treatment. By demonstrating this, I further validate the use of OTCs as a technique for studying climate change effects on reproduction in Arctic plant communities, and suggest that reproductive data from OTC-warmed Arctic plant communities are likely representative of future warmed climates. The only exception to this may be early flowering self-incompatibly plants such as Saxifraga oppositifolia. (Stenströmet al., 1997) showed that even minor changes in S. oppositifolia reproductive phenology occur at such early periods that pollination is reduced due to mismatches between pollinator emergence and flowering time. Other authors have implied that other early-flowering plants may be subjected to artificial pollen limitation within OTCs (Stenströmand Molau, 1992; Jones et al., 1997). Both insect and flower emergence in Arctic ecosystems is generally tied to snowmelt rather than temperature (Molau, 1993; Walker et al., 1999; Totland and Alatalo, 2002; Dollery et al., 2006; Høye et al., 2007; Høye and Forchham- mer, 2008), but Høye et al. (2013) identified that climate-induced changes in

68 Chapter 4. Conclusions phenology tend to shift phenology in late-flowering populations more than early-flowering populations. I also examined the temporal structure of an Arctic plant-pollinator network, showing that the Syrphidae and the Muscidae constituted the most common floral visitors at the site, and that Bombus polaris plays a much reduced role (in terms of catches/hr). I showed that Dryas integrifolia does not appear to constitute a limiting resource for insect visitors, while Papaver radicatum is much more important to insect visitors, especially the Syrphi- dae. Using bowl-trapping, I demonstrated that OTCs significantly reduced catches of visiting insects, as well as other common flying insects. However, in the context of the results of experimental pollination manipulation, this reduction is probably not ecologically significant (except for early-flowering plants). Finally, I showed that OTC warming tended to shorten the flowering season for D. integrifolia, while lengthening the flowering season and increasing the flower density of P. radicatum. This implies that insect visitation could be enhanced later in the season under a future warmed climate, but much of this depends on the timing and duration of pollinator emergence. Whether shifts in plant phenology will actually decouple Arctic plant- pollinator networks has yet to be seen, as most previous studies did not conduct actual netting or visitor observations, but used bowl or pit trap catch rates as a proxy for visitation. Bowl-trapping and pit-trapping are relatively easy ways to collect insects but yield no actual information on plant-insect interactions, and are more useful as a measure of relative population size. I did not find that insect population was a proxy of catch rates for any species except Dryas integrifolia, implying that visitation rates depend on other factors such as floral availability and environmental variables. Thus, future studies should examine actual visitation rates to better understand pollination rates, and avoid using bowl trapping rates as a “proxy of a proxy of pollination”. Netting was not conducted inside of OTCs because of the danger it posed to the long-term study plants, the instrumentation present in the plots, as well as the inherent inaccuracy in comparing large area captures to small area captures. Measuring the actual visitation rate of insects to flowers inside and outside of OTCs is highly tedious work involving manually observ- ing clusters of flower for long periods of time, recording visit rates of various insects. Video capture of visiting insects is a relatively new field, but has been used by some authors to investigate detailed insect visitation patterns (Steen and Thorsdatter, 2011; Lortie et al., 2012). I conducted time-lapse photography (5-second interval) of groups of flowers both inside and outside

69 Chapter 4. Conclusions the OTCs, using GoPro R HERO 1 cameras with an attached battery pack. These cameras were able to capture 12 hours of continuous data, and I conducted observations over the span of the growing season, concurrently with netting and bowl trapping. I have also devised an image-processing program that is able to determine threshold ed changes in intensity associated with dark-coloured insects landing on a brightly-coloured flower. The problem of flower motion due to wind is difficult to handle, but there are several classi- fication schemes that may be able to handle this process. However, due to time constraints I was not able to complete an analyses of this method, and it is not part of this thesis. In addition to monitoring plant-pollinator interactions, an effort should be made to further understand the ecology of Arctic insect communities, rather than solely descriptive studies. Aphids, midges, gall-wasps, stem- borers, leaf-miners, thrips, and caterpillars are all part of the Arctic herbiv- orous insect community, but their role has been far less studied than that of ungulate or avian grazers. Predatory flies and parasitic wasps most likely play a large role in regulating their populations (Kukal and Kevan, 1987). Spiders, in particular, are well-noted in Arctic arthropod collections (Leech and Ryan, 1972), but their ecological role has been studied to a very small extent. Hodkinson et al. (2001) links their activities to establishment and early plant community development, they form the base of the food web for many Arctic birds, and they are seen hunting insects throughout all parts of the snow-free season (personal observation). Clearly they play a role in the overall community, but this role is almost completely unstudied. The effects of OTCs on plant growth and development are fairly well- established (Wookey et al., 1995; Jones et al., 1997; Welker et al., 1997; Mølgaard and Christensen, 1997; Stenströmet al., 1997), along with changes in community structure (Wookey et al., 1993; Hudson and Henry, 2010; Elmendorf et al., 2012a). However, changes in life history and population dynamics are not well understood in the context of OTC warming. As suggested by Cooper et al. (2004) and Mülleret al. (2011), germination should be examined in the context of OTC warming to examine how induced warming changes rates of establishment. This is a key piece of ecological knowledge that has heretofore been unstudied. Seed germination studies in the context of Arctic warming often yield dissimilar results, which can be dependent on year-to-year and site-to-site variation (Molau and Shaver, 1997; Welker et al., 1997; Molau, 1997; Mølgaard and Christensen, 1997; Mülleret al., 2011; Klady et al., 2011). Milbau et al. (2009) found that seed germination occurred earlier, but not at higher rates, in warmed soils, implying that future seed establishment will take place earlier in the year.

70 Chapter 4. Conclusions

Depending on local moisture conditions, this has the potential to increase or decrease survival, as most seedling mortality occurs due to summer drought (Bliss, 1958; Bell and Bliss, 1980). While changes to established plant communities are of great importance, new habitats will become available for colonization by plants as the Arctic warms, especially in the High Arctic. How these ranges will be colonized depends on reproduction and establishment by adjacent plants. In this way, it is important to understand the mechanisms that lead to establishment, including pollination, seed formation, and dispersal. Insects have the potential to alter patterns of pollination, especially in early-ﬂowering plants. Thus, the continued study of plant-pollinator relationships is important to understanding aspects of future Arctic ecosystems.

71 Bibliography

Alatalo, J. and Totland, O. 1997. Response to simulated climatic change in an alpine and subarctic pollen-risk strategist, Silene acaulis. Global Change Biology, 3(S1):74–79.

Alexeev, V. A., Esau, I., Polyakov, I. V., Byam, S. J., and Sorokina, S. 2012. Vertical structure of recent Arctic warming from observed data and reanalysis products. Climatic change, 111(2):215–239.

Anderson, D. R. 2008. Model based inference in the life sciences: a primer on evidence. Springer.

Avila-Jim´enez,M.´ and Coulson, S. 2011. Can snow depth be used to predict the distribution of the high Arctic aphid Acyrthosiphon svalbardicum (Hemiptera: Aphididae) on Spitsbergen? BMC Ecology, 11(1):25.

Bates, D., Maechler, M., Bolker, B., and Walker, S. 2013. lme4: Linear mixed-eﬀects models using Eigen and S4. R package version 1.0-4.

Bell, K. L. and Bliss, L. C. 1980. Plant reproduction in a high Arctic environment. Arctic and Alpine Research, 12(1):1–10.

Berenbaum, M., Bernhardt, P., Buchmann, S., Calderone, N., Goldstein, P., Inouye, D., Kevan, P., Kremen, C., Medellin, R., Ricketts, T., and others. 2007. Status of pollinators in North America. The National Academies Press.

Bergman, P., Molau, U., and Holmgren, B. 1996. Micrometeorological impacts on insect activity and plant reproductive success in an alpine environment, Swedish Lapland. Arctic and Alpine Research, 28(2):196–202.

Billings, W. D. and Mooney, H. A. 1968. The ecology of Arctic and alpine plants. Biological Reviews, 43(4):481–529.

Bjorkman, A., Henry, G., and Vellend, M. 2013. Migration potential of tundra plant species in a warming Arctic: responses of southern ecotypes

72 Bibliography

of three species to experimental warming in the high Arctic. In EGU General Assembly Conference Abstracts, volume 15, page 548.

Bliss, L. 1958. Seed germination in Arctic and alpine species. Arctic, 11(3):180–188.

Blok, D., Heijmans, M., Schaepman-Strub, G., Kononov, A., Maximov, T., and Berendse, F. 2010. Shrub expansion may reduce summer permafrost thaw in Siberian tundra. Global Change Biology, 16(4):1296–1305.

Bocher, J. 1996. Further insect studies. In The ITEX Manual, chapter 10, pages 37–38. Danish Polar Center, Copenhagen, 2nd edition.

Bolker, B. M., Brooks, M. E., Clark, C. J., Geange, S. W., Poulsen, J. R., Stevens, M. H. H., and White, J.-S. S. 2009. Generalized linear mixed models: a practical guide for ecology and evolution. Trends in ecology & evolution, 24(3):127–135.

Breen, K. and L´evesque, E. 2006. Proglacial succession of biological soil crusts and vascular plants: biotic interactions in the High Arctic. Cana- dian Journal of Botany, 84(11):1714–1731.

Brochmann, C., Edwards, M. E., and Alsos, I. G. 2013. The Balance of Nature and Human Impact, chapter The dynamic past and future of Arctic plants: climate change, spatial variation, and genetic diversity, pages 133– 152. Cambridge University Press.

Burnham, K. P. and Anderson, D. R. 2002. Model selection and multi-model inference: a practical information-theoretic approach. Springer.

CANPOLIN 2009. CANPOLIN Sampling Protocols.

Chapin, F. S. 1983. Direct and indirect eﬀects of temperature on arctic plants. Polar Biology, 2:47–52.

Chernov, Y. 1995. Diversity of the Arctic terrestrial fauna. In Chapin, F. S. and K¨orner,C., editors, Arctic and alpine biodiversity: patterns, causes and ecosystem consequences, volume 113 of Ecological Studies, chapter Diversity of the Arctic Terrestrial Fauna, pages 81–95. Springer Berlin Heidelberg.

Chernov, Y. I. 1966. Kompleks antoﬁl’nykh nasekomykh v tundrovoy zone [Complex of anthophilous insects in the tundra zone]. Voprosy geograﬁi, 69(1-2):279–307.

73 Bibliography

Chernov, Y. I. 1985. The Living Tundra. Studies in polar research. Cam- bridge University Press, Cambridge; New York.

Chinnappa, C., Donald, G. M., Sasidharan, R., and Emery, R. N. 2005. The biology of Stellaria longipes (Caryophyllaceae). Botany, 83(11):1367–1383.

Cooper, E. J., Alsos, I. G., Hagen, D., Smith, F. M., Coulson, S. J., and Hod- kinson, I. D. 2004. Plant recruitment in the high Arctic: seed bank and seedling emergence on Svalbard. Journal of Vegetation Science, 15(1):115– 124.

Corbett, A. L., Krannitz, P. G., and Aarssen, L. W. 1992. The inﬂuence of petals on reproductive success in the arctic poppy (Papaver radicatum). Canadian Journal of Botany, 70(1):200–204.

Culley, T. M., Weller, S. G., and Sakai, A. K. 2002. The evolution of wind pollination in angiosperms. Trends in Ecology & Evolution, 17(8):361–369.

Dang, T. T. T. and Chinnappa, C. 2007. The reproductive biology of Stel- laria longipes Goldie (Caryophyllaceae) in North America. Flora - Mor- phology, Distribution, Functional Ecology of Plants, 202(5):403–407.

Danks, H., Kukal, O., and Ring, R. 1994. Insect cold-hardiness: insights from the Arctic. Arctic, 47:391–404.

Danks, H. V. 1992. Arctic Insects as Indicators of Environmental Change. Arctic, 45(2):159–166.

Danks, H. V. 1996. The wider integration of studies on insect cold-hardiness. European Journal of Entomology, 93:383–404.

Danks, H. V. 2004. Seasonal Adaptations in Arctic Insects. Integrative and Comparative Biology, 44(2):85 –94.

Darwin, C. 1859. The origin of species by means of natural selection. John Murray.

Darwin, C. 1862. The various contrivances by which orchids are fertilised by insects. John Murray.

Dawson, T. E. and Bliss, L. 1989a. Intraspeciﬁc variation in the water relations of Salix arctica, an Arctic-alpine dwarf willow. Oecologia, 79(3):322– 331.

74 Bibliography

Dawson, T. E. and Bliss, L. 1989b. Patterns of water use and the tissue water relations in the dioecious shrub, Salix arctica: the physiological basis for habitat partitioning between the sexes. Oecologia, 79(3):332–343.

Densmore, R. and Zasada, J. 1983. Seed dispersal and dormancy patterns in northern willows: ecological and evolutionary signiﬁcance. Canadian Journal of Botany, 61(12):3207–3216.

Dollery, R., Hodkinson, I. D., and J´onsd´ottir,I. S. 2006. Impact of warming and timing of snow melt on soil microarthropod assemblages associated with Dryas-dominated plant communities on Svalbard. Ecography, 29(1):111–119.

Donnelly, A., Caﬀarra, A., and ONeill, B. F. 2011. A review of climate- driven mismatches between interdependent phenophases in terrestrial and aquatic ecosystems. International Journal of Biometeorology, 55(6):805– 817.

Downes, J. A. 1964. Arctic Insects and Their Environment. The Canadian Entomologist, 96:279–307.

Elberling, H. and Olesen, J. M. 1999. The structure of a high latitude plant- ﬂower visitor system: the dominance of ﬂies. Ecography, 22(3):314–323.

Elliott, S. E. 2009. Subalpine bumble bee foraging distances and densities in relation to ﬂower availability. Environmental entomology, 38(3):748–756.

Elmendorf, S. C., Henry, G. H., Hollister, R. D., Bj¨ork,R. G., Boulanger- Lapointe, N., Cooper, E. J., Cornelissen, J. H., Day, T. A., Dorrepaal, E., Elumeeva, T. G., et al. 2012a. Plot-scale evidence of tundra vegetation change and links to recent summer warming. Nature Climate Change, 2(6):453–457.

Elmendorf, S. C., Henry, G. H. R., Hollister, R. D., Bjrk, R. G., Bjorkman, A. D., Callaghan, T. V., Collier, L. S., Cooper, E. J., Cornelissen, J. H. C., et al. 2012b. Global assessment of experimental climate warming on tundra vegetation: heterogeneity over space and time. Ecology Letters, 15(2):164–175.

Epstein, H. E., Walker, M. D., Chapin III, F. S., and Starﬁeld, A. M. 2000. A transient, nutrient-based model of Arctic plant community response to climatic warming. Ecological Applications, 10(3):824–841.

75 Bibliography

Eriksson, O. and Fr¨oborg, H. 1996. ” Windows of opportunity” for recruitment in long-lived clonal plants: experimental studies of seedling establishment in Vaccinium shrubs. Canadian Journal of Botany, 74(9):1369– 1374.

Faegri, K. and Van der Pijl, L. 1979. The Principles of Pollination Ecology. Pergamon international library of science, technology, engineering and social studies. Pergamon Press, Oxford; New York, 3rd revised edition.

Fournier, D. A., Skaug, H. J., Ancheta, J., Ianelli, J., Magnusson, A., Maunder, M. N., Nielsen, A., and Sibert, J. 2012. AD Model Builder: using automatic diﬀerentiation for statistical inference of highly param- eterized complex nonlinear models. Optimization Methods and Software, 27(2):233–249.

Franz´en,M. and Ockinger,¨ E. 2012. Climate-driven changes in pollinator assemblages during the last 60 years in an Arctic mountain region in Northern Scandinavia. Journal of Insect Conservation, 16(2):227–238.

Freedman, B., Hill, N., Svoboda, J., and Henry, G. 1982. Seed banks and seedling occurrence in a high arctic oasis at Alexandra Fjord, Ellesmere Island, Canada. Canadian Journal of Botany, 60(10):2112–2118.

Gaston, A. J., Gilchrist, H. G., and Hipfner, J. M. 2005. Climate change, ice conditions and reproduction in an Arctic nesting marine bird: Brunnich’s guillemot (Uria lomvia L.). Journal of Animal Ecology, 74(5):832–841.

Gelbi˘c,I. and Olejn´ı˘cek,J. 2011. Ecology of Dolichopodidae (Diptera) in a wetland habitat and their potential role as bioindicators. Central European Journal of Biology, 6(1):118–129.

Ghazoul, J. 2006. Floral diversity and the facilitation of pollination. Journal of Ecology, 94(2):295–304.

Gilbert, F. S. 1985. Diurnal activity patterns in hoverﬂies (Diptera: Syrphi- dae). Ecological Entomology, 10(4):385–392.

Gillespie, M. A. K., J´onsd´ottir,I. S., Hodkinson, I. D., and Cooper, E. J. 2013. Aphid-willow interactions in a high Arctic ecosystem: responses to raised temperature and goose disturbance. Global Change Biology, 19(12):3698–3708.

76 Bibliography

Graversen, R. G., Mauritsen, T., Tjernström,M., Källén, E., and Svens- son, G. 2008. Vertical structure of recent Arctic warming. Nature, 451(7174):53–56. Grime, J. P. 1977. Evidence for the Existence of Three Primary Strategies in Plants and Its Relevance to Ecological and Evolutionary Theory. The American Naturalist, 111(982):1169–1194. Gugerli, F. 1998. Effect of elevation on sexual reproduction in alpine populations of Saxifraga oppositifolia (Saxifragaceae). Oecologia, 114(1):60–66. Hadfield, J. D. 2010. MCMC Methods for Multi-Response Generalized Lin- ear Mixed Models: The MCMCglmm R Package. Journal of Statistical Software, 33(2):1–22. Halekoh, U., Højsgaard, S., and Yan, J. 2006. The R package geepack for generalized estimating equations. Journal of Statistical Software, 15(2):1– 11. Hardin, J. W. and Hilbe, J. M. 2003. Generalized estimating equations. Wiley Online Library. Hassol, S. J. 2004. Impacts of a warming Arctic: Arctic Climate Impact Assessment. Cambridge University Press. Hegland, S. J., Nielsen, A., Lázaro,A., Bjerknes, A.-L., and Totland, Ø. 2009. How does climate warming affect plant-pollinator interactions? Ecology Letters, 12(2):184–195. Hegland, S. J. and Totland, Ø. 2005. Relationships between species floral traits and pollinator visitation in a temperate grassland. Oecologia, 145(4):586–594. Heinrich, B. 1975. Energetics of Pollination. Annual Review of Ecology and Systematics, 6:139–170. Heinrich, B. 1983. Insect Foraging Energetics, pages 187–214. Scientific and Academic Editions. Henry, G. H. R. and Molau, U. 1997. Tundra plants and climate change: the International Tundra Experiment (ITEX). Global Change Biology, 3(S1):1–9. Herrera, C. M. 1987. Components of Pollinator ”Quality”: Comparative Analysis of a Diverse Insect Assemblage. Oikos, 50(1):79–90.

77 Bibliography

Hilbe, J. M. 1994. Generalized linear models. The American Statistician, 48(3):255–265.

Hilbe, J. M. 2011. Negative binomial regression. Cambridge University Press.

Hill, G. B. and Henry, G. H. 2011. Responses of High Arctic wet sedge tundra to climate warming since 1980. Global Change Biology, 17(1):276–287.

Hinzman, L. D., Bettez, N. D., Bolton, W. R., Chapin, F. S., Dyurgerov, M. B., Fastie, C. L., Griﬃth, B., Hollister, R. D., Hope, A., Huntington, H. P., et al. 2005. Evidence and implications of recent climate change in northern Alaska and other arctic regions. Climatic Change, 72(3):251–298.

Hocking, B. 1968. Insect-ﬂower associations in the High Arctic with special reference to nectar. Oikos, 19(2):359–387.

Hocking, B. and Sharpin, C. D. 1965. Flower Basking by Arctic Insects. Nature, 206(4980):215.

Hodkinson, I. D., Coulson, S. J., Harrison, J., and Webb, N. R. 2001. What a wonderful web they weave: spiders, nutrient capture and early ecosystem development in the high Arctic some counter-intuitive ideas on community assembly. Oikos, 95(2):349–352.

Holling, C. S. 1973. Resilience and stability of ecological systems. Annual review of ecology and systematics, 4:1–23.

Hollister, R. D. and Webber, P. J. 2000. Biotic validation of small open-top chambers in a tundra ecosystem. Global Change Biology, 6(7):835–842.

Holzschuh, A., Steffan-Dewenter, I., Kleijn, D., and Tscharntke, T. 2007. Diversity of flower-visiting bees in cereal fields: effects of farming system, landscape composition and regional context. Journal of Applied Ecology, 44(1):41–49.

Høye, T. T., Ellebjerg, S. M., and Philipp, M. 2007. The Impact of Climate on Flowering in the High Arcticthe Case of Dryas in a Hybrid Zone. Arctic, Antarctic, and Alpine Research, 39(3):412–421.

Høye, T. T. and Forchhammer, M. C. 2008. High-arctic Ecosystem Dynam- ics in a Changing Climate, volume 40, chapter Phenology of High-Arctic Arthropods: Eﬀects of Climate on Spatial, Seasonal, and Inter-Annual Variation, pages 299–322. Academic Press.

78 Bibliography

Høye, T. T., Post, E., Schmidt, N. M., Trøjelsgaard, K., and Forchhammer, M. C. 2013. Shorter ﬂowering seasons and declining abundance of ﬂower visitors in a warmer Arctic. Nature Climate Change, 3(8):759–763.

Hudson, J. M. and Henry, G. H. 2010. High Arctic plant community resists 15 years of experimental warming. Journal of Ecology, 98(5):1035–1041.

Hudson, J. M. G. and Henry, G. H. R. 2009. Increased plant biomass in a High Arctic heath community from 1981 to 2008. Ecology, 90:2657–2663.

Jepsen, J., Kapari, L., Hagen, S., Schott, T., Vindstad, O., Nilssen, A., and Ims, R. 2011. Rapid northwards expansion of a forest insect pest attributed to spring phenology matching with sub-Arctic birch. Global Change Biology, 17(6):2071–2083.

Jepsen, J. U., Hagen, S. B., Ims, R. A., and Yoccoz, N. G. 2008. Climate change and outbreaks of the geometrids Operophtera brumata and Epir- rita autumnata in subarctic birch forest: evidence of a recent outbreak range expansion. Journal of Animal Ecology, 77(2):257–264.

Jervis, M. A. and Kidd, N. A. C. 1986. Host-feeding Strategies In Hy- menopteran Parasitoids. Biological Reviews, 61(4):395–434.

Jones, M. 1995. Experimental investigations into eﬀects of climate change on High Arctic plants. PhD thesis, University of Alberta, Edmonton.

Jones, M., Bay, C., and Nordenh¨all,U. 1997. Eﬀects of experimental warming on arctic willows (Salix spp.): a comparison of responses from the Canadian High Arctic, Alaskan Arctic, and Swedish Subarctic. Global Change Biology, 3(S1):55–60.

Jones, M. H., MacDonald, S. E., and Henry, G. H. 1999. Sex-and habitat- speciﬁc responses of a high arctic willow, Salix arctica, to experimental climate change. Oikos, 87:129–138.

Karlsson, L. M. and Milberg, P. 2007. A comparative study of germination ecology of four Papaver taxa. Annals of Botany, 99(5):935–946.

Kearns, C. A. 2001. North American dipteran pollinators: assessing their value and conservation status. Conservation Ecology, 5(1):5.

Kevan, P. 1990. Sexual diﬀerences in temperatures of blossoms on a dioecious plant, Salix arctica: signiﬁcance for life in the arctic. Arctic and Alpine Research, 22:283–289.

79 Bibliography

Kevan, P. and Kevan, D. 1970. Collembola as pollen feeders and ﬂower visitors with observations from the high Arctic. Quaestiones Entomologicae, 6:311–326.

Kevan, P. G. 1972a. Floral colors in the High Arctic with reference to insect-ﬂower relations and pollination. Canadian Journal of Botany, 50(11):2289–2316.

Kevan, P. G. 1972b. Insect pollination of High Arctic ﬂowers. Journal of Ecology, 60(3):831–847.

Kevan, P. G. 1973a. Flowers, insects, and pollination ecology in the Cana- dian High Arctic. Polar Record, 16(104):667–674.

Kevan, P. G. 1973b. Parasitoid Wasps as Flower Visitors in the Canadian High Arctic. Anzeiger fürSchädlingskunde, Pflanzen- und Umweltschutz, 46(1):3–7.

Kevan, P. G. 1975. Sun-tracking solar furnaces in High Arctic ﬂowers: sig- niﬁcance for pollination and insects. Science, 189(4204):723 –726.

Kjellberg, B., Karlsson, S., and Kerstensson, I. 1982. Eﬀects of heliotropic movements of ﬂowers of Dryas octopetala L. on gynoecium temperature and seed development. Oecologia, 54(1):10–13.

Klady, R. A. 2006. Long-term experimental warming eﬀects on tundra plant sexual reproduction in the high Arctic. Master’s thesis, University of British Columbia.

Klady, R. A., Henry, G. H. R., and Lemay, V. 2011. Changes in High Arctic tundra plant reproduction in response to long-term experimental warming. Global Change Biology, 17(4):1611–1624.

Klanderud, K. and Totland, Ø. 2005. Simulated climate change altered dominance hierarchies and diversity of an alpine biodiversity hotspot. Ecology, 86(8):2047–2054.

Krannitz, P. 1996. Reproductive ecology of Dryas integrifolia in the high Arctic semi-desert. Canadian journal of botany, 74(9):1451–1460.

Kudo, G. 1993. Relationships between ﬂowering time and fruit set of the en- tomophilous alpine shrub, Rhododendron aureum (Ericaceae), inhabiting snow patches. American Journal of Botany, 80(11):1300–1304.

80 Bibliography

Kukal, O. and Kevan, P. G. 1987. The inﬂuence of parasitism on the life history of a high arctic insect, Gynaephora groenlandica (W¨ocke)(Lepidoptera: Lymantriidae). Canadian Journal of Zoology, 65:156–163.

Laird, N. M. and Ware, J. H. 1982. Random-eﬀects models for longitudinal data. Biometrics, 38:963–974.

Larson, B., Kevan, P., and Inouye, D. 2001. Flies and ﬂowers: taxonomic diversity of anthophiles and pollinators. The Canadian Entomologist, 133(04):439–465.

Leech, R. and Ryan, J. 1972. Notes on Canadian Arctic spiders (Araneida), mainly from Devon island, NWT. The Canadian Entomolo- gist, 104(11):1787–1791.

L´evesque, E., Henry, G., and Svoboda, J. 1997. Phenological and growth responses of Papaver radicatum along altitudinal gradients in the Canadian High Arctic. Global Change Biology, 3(S1):125–145.

Liang, K.-Y. and Zeger, S. L. 1986. Longitudinal data analysis using generalized linear models. Biometrika, 73(1):13–22.

Lortie, C., Budden, A., and Reid, A. 2012. From birds to bees: apply- ing video observation techniques to invertebrate pollinators. Journal of Pollination Ecology, 6(0):125–128.

Losey, J. E. and Vaughan, M. 2006. The economic value of ecological services provided by insects. Bioscience, 56(4):311–323.

L¨ove, D. 1969. Papaver at high altitudes in the rocky mountains. Brittonia, 21(1):1–10.

Lund, M., Falk, J. M., Friborg, T., Mbufong, H. N., Sigsgaard, C., Soe- gaard, H., and Tamstorf, M. P. 2012. Trends in CO2 exchange in a high Arctic tundra heath, 2000–2010. Journal of Geophysical Research: Bio- geosciences, 117(G2).

Lundberg, H. 1980. Eﬀects of weather on foraging-ﬂights of bumblebees (Hymenoptera, Apidae) in a subalpine/alpine area. Ecography, 3(2):104– 110.

Lundberg, H. and Ranta, E. 1980. Habitat and food utilization in a subarctic bumblebee community. Oikos, 35(3):303–310.

81 Bibliography

Lundgren, R. and Olesen, J. 2005. The Dense and Highly Connected World of Greenland’s Plants and Their Pollinators. Arctic, Antarctic, and Alpine Research, 37(4):514–520. MacArthur, R. H. 1967. The theory of island biogeography, volume 1. Prince- ton University Press. MacArthur, R. H. 1972. Geographical Ecology. Harper and Row. MacDonald, G. M. 2010. Global warming and the Arctic: a new world beyond the reach of the Grinnellian niche? The Journal of Experimental Biology, 213(6):855–861. Marion, G., Henry, G., Freckman, D., Johnstone, J., Jones, G., Jones, M., Levesque, E., Molau, U., Mølgaard, P., Parsons, A., Svoboda, J., and Virginia, R. 1997. Open-top designs for manipulating field temperature in high-latitude ecosystems. Global Change Biology, 3(S1):20–32. Mathiesen, F. 1921. The structure and biology of arctic flowering plants. 15. Scrophulariaceae. Meddelelser om Gronland, 37:359–507. McLeod, A. 2011. Kendall rank correlation and Mann-Kendall trend test. R package version 2.2. Mesler, M. R., Ackerman, J. D., and Lu, K. L. 1980. The Effectiveness of Fungus Gnats as Pollinators. American Journal of Botany, 67(4):564–567. Milbau, A., Graae, B. J., Shevtsova, A., and Nijs, I. 2009. Effects of a warmer climate on seed germination in the subarctic. Annals of Botany, 104(2):287–296. Miller, J., Henning, L., Heazlewood, V., Larkin, P. J., Chitty, J., Allen, R., Brown, P. H., Gerlach, W., and Fist, A. 2005. Pollination biology of oilseed poppy, Papaver somniferum L. Crop and Pasture Science, 56(5):483–490. Moise, E. R. D. and Henry, H. A. L. 2010. Like moths to a street lamp: exaggerated animal densities in plot-level global change field experiments. Oikos, 119(5):791–795. Molau, U. 1993. Relationships between flowering phenology and life history strategies in tundra plants. Arctic and Alpine Research, 25:391–402. Molau, U. 1997. Responses to natural climatic variation and experimental warming in two tundra plant species with contrasting life forms: Cassiope tetragona and Ranunculus nivalis. Global Change Biology, 3(S1):97–107.

82 Bibliography

Molau, U. and Mølgaard, P., editors 1996. International tundra experiment (ITEX) manual. Danish Polar Center, Copenhagen, 2nd edition.

Molau, U. and Shaver, G. 1997. Controls on Seed Production and Seed Ger- minability in Eriophorum vaginatum. Global Change Biology, 3(S1):80–88.

Mølgaard, P. 1989. Temperature relations of yellow and white ﬂowered Papaver radicatum in north Greenland. Arctic and Alpine Research, 21(1):83–90.

Mølgaard, P. and Christensen, K. 1997. Response to experimental warming in a population of Papaver radicatum in Greenland. Global Change Biology, 3(S1):116–124.

Mølgaard, P. and Morewood, D. W. 1996. ITEX Insect: Gynaephora groenlandica/ G. rossii. In The ITEX Manual, page 85. Danish Polar Center, Copenhagen, 2 edition.

Morewood, D. W. and Ring, R. A. 1998. Revision of the life history of the High Arctic moth Gynaephora groenlandica (Wocke) (Lepidoptera: Lymantriidae). Canadian Journal of Zoology, 76(7):1371–1381.

Morton, D. C., Masek, J. G., Wang, D., Sexton, J. O., Nagol, J. R., Ropars, P., Boudreau, S., et al. 2012. Satellite-based evidence for shrub and graminoid tundra expansion in northern Quebec from 1986 to 2010. Global Change Biology, 18(7):2313–2323.

Mosquin, T. and Martin, J. 1967. Observations on the pollination biology of plants on Melville Island, NWT, Canada. Canadian Field Naturalist, 81:201–205.

Muc, M., Freedman, B., and Svoboda, J. 1989. Vascular plant communities of a polar oasis at Alexandra Fiord(79 degree N), Ellesmere Island, Canada. Canadian Journal of Botany, 67(4):1126–1136.

M¨uller,E., Cooper, E. J., and Alsos, I. G. 2011. Germinability of Arctic plants is high in perceived optimal conditions but low in the ﬁeld. Botany, 89(5):337–348.

Myers-Smith, I. H., Forbes, B. C., Wilmking, M., Hallinger, M., Lantz, T., Blok, D., Tape, K. D., Macias-Fauria, M., Sass-Klaassen, U., L´evesque, E., et al. 2011. Shrub expansion in tundra ecosystems: dynamics, impacts and research priorities. Environmental Research Letters, 6(4):045509.

83 Bibliography

Neuhaus, J. and McCulloch, C. 2011. Generalized linear models. Wiley Interdisciplinary Reviews: Computational Statistics, 3(5):407–413.

Nordal, I., Hestmark, G., and Solstad, H. 1997. Reproductive biology and demography of Papaver radicatum: a key species in Nordic plant geography. Opera Botanica, 132(132):77–87.

Oberbauer, S., Elmendorf, S., Troxler, T. G., Hollister, R. D., Rocha, A. V., Bret-Harte, M. S., Dawes, M. A., Fosaa, A. M., Henry, G. H. R., Høye, T. T., Jarrad, F. C., J´onsd´ottir,I. S., Klanderud, K., Klein, J. A., Molau, U., Rixen, C., Schmidt, N. M., Shaver, G. R., Slider, R. T., Totland, Ø., Wahren, C. H., and Welker, J. M. 2013. Phenological response of tundra plants to background climate variation tested using the International Tundra Experiment. Philosophical Transactions of the Royal Society B: Biological Sciences, 368(1624):20120481.

Oberbauer, S. F., Tweedie, C. E., Welker, J. M., Fahnestock, J. T., Henry, G. H., Webber, P. J., Hollister, R. D., Walker, M. D., Kuchy, A., Elmore, E., et al. 2007. Tundra CO2 ﬂuxes in response to experimental warming across latitudinal and moisture gradients. Ecological Monographs, 77(2):221–238.

Oechel, W. C., Vourlitis, G. L., Hastings, S. J., Zulueta, R. C., Hinz- man, L., and Kane, D. 2000. Acclimation of ecosystem CO2 exchange in the Alaskan Arctic in response to decadal climate warming. Nature, 406(6799):978–981.

Oksanen, J., Blanchet, F. G., Kindt, R., Legendre, P., Minchin, P. R., O’Hara, R. B., Simpson, G. L., Solymos, P., Stevens, M. H. H., and Wagner, H. 2013. Vegan: Community Ecology Package. R package version 2.0-10.

Olesen, J., Bascompte, J., Elberling, H., and Jordano, P. 2008. Temporal dynamics in a pollination network. Ecology, 89(6):1573–1582.

Oliver, D. R. 1963. Entomological Studies in the Lake Hazen Area, Ellesmere Island, including Lists of Species of Arachnida, Collembola, and Insecta. Arctic, 16(3):175–180.

Olson, A. R. and Richards, J. H. 1979. Temperature Responses of Germi- nation in Arctic Poppy (Papaver radicatum Rottb.) Seeds. Arctic and Alpine Research, 11(3):343–348.

84 Bibliography

Patra, N., Ram, R., Chauhan, S., and Singh, A. 1992. Quantitative studies on the mating system of opium poppy (Papaver somniferum L.). Theo- retical and Applied Genetics, 84(3-4):299–302.

Peeters, L. and Totland, Ø. 1999. Wind to insect pollination ratios and ﬂoral traits in ﬁve alpine Salix species. Canadian Journal of Botany, 77(4):556–563.

Philipp, M. 1980. reproductive biology of Stellaria longipes Goldie as revealed by a cultivation experiment. New Phytologist, 85(4):557–569.

Philipp, M., B¨ocher, J., Mattsson, O., and Woodell, S. R. J. 1990. A quantitative approach to the sexual reproductive biology and population structure in some arctic ﬂowering plants: Dryas integrifolia, Silene acaulis and Ranunculus nivalis. Meddelelser om Grønland, 34:1–60.

Philipp, M. and Siegismund, H. R. 2003. What can morphology and isozymes tell us about the history of the Dryas integrifolia–octopetala complex? Molecular Ecology, 12(8):2231–2242.

Philipp, M., Woodell, S. R. J., Bcher, J., and Mattsson, O. 1996. Repro- ductive Biology of Four Species of Pedicularis (Scrophulariaceae) in West Greenland. Arctic and Alpine Research, 28(4):403–413.

Pinheiro, J. C. and Bates, D. M. 2000. Linear mixed-eﬀects models: basic concepts and examples. Springer.

Pont, A. 1993. Observations on anthophilous Muscidae and other Diptera (Insecta) in Abisko National Park, Sweden. Journal of natural history, 27(3):631–643.

Porsild, A. E. and Cody, W. J. 1980. Vascular Plants of Continental North- west Territories, Canada. Ottawa: National Museums of Canada.

Post, E. and Forchhammer, M. C. 2008. Climate change reduces reproductive success of an Arctic herbivore through trophic mismatch. Philosophical Transactions of the Royal Society B: Biological Sciences, 363(1501):2367–2373.

Post, E., Forchhammer, M. C., Bret-Harte, M. S., Callaghan, T. V., Chris- tensen, T. R., Elberling, B., Fox, A. D., Gilg, O., Hik, D. S., Høye, T. T., et al. 2009. Ecological dynamics across the Arctic associated with recent climate change. Science, 325(5946):1355–1358.

85 Bibliography

Price, P. W. 1997. Insect ecology. John Wiley & Sons.

Proctor, M. C. F., Yeo, P., and Lack, A. 1996. The Natural History of Pollination. Timber Press, Portland, OR.

R Core Team 2013. R: A Language and Environment for Statistical Com- puting. R Foundation for Statistical Computing, Vienna, Austria.

Richards, K. 1973. Biology of Bombus polaris Curtis and Bombus hyper- boreus Schonherr at Lake Hazen, Northwest Territories (Hymenoptera: Bombini). Quaestiones Entomologicae, 9:115–157.

Richardson, S. J., Press, M. C., Parsons, A. N., and Hartley, S. E. 2002. How do nutrients and warming impact on plant communities and their insect herbivores? A 9-year study from a sub-Arctic heath. Journal of Ecology, 90(3):544–556.

Ring, R. A. 2001. Arctic Insects, Global Warming and the ITEX Program. Newsletter of the Biological Survey of Canada (Terrestrial Arthropods), 20(1):17–23.

Robinson, S. V. 2011. Plant-Pollinator Interactions at Alexandra Fiord, Nunavut. Trail Six: An Undergraduate Journal of Geography, 5:13 – 20.

Roslin, T., Wirta, H., Hopkins, T., Hardwick, B., and V´arkonyi, G. 2013. Indirect interactions in the high arctic. PloS one, 8(6):e67367.

Sahli, H. F. and Conner, J. K. 2007. Visitation, eﬀectiveness, and eﬃciency of 15 genera of visitors to wild radish, Raphanus raphanistrum (Brassi- caceae). American Journal of Botany, 94(2):203–209.

Schowalter, T. D. 2006. Insect ecology: an ecosystem approach. Academic Press.

Serreze, M. C., Barrett, A. P., Stroeve, J. C., Kindig, D. N., and Holland, M. M. 2009. The emergence of surface-based Arctic ampliﬁcation. The Cryosphere, 3(1):11–19.

Simpson, B., Neff, J., Jones, C., and Little, R. 1983. Evolution and diversity of floral rewards. In Handbook of Experimental Pollination Biology, pages 142–159. Scientific and Academic Editions.

Solstad, H., Elven, R., and Nordal, I. 1999. Are there too many species and subspecies in the Papaver radicatum complex? In Nordal, I. and

86 Bibliography

Razzhivin, V., editors, The Species Concept in the High North - a Panar- ctic Flora Initiative, volume 38, pages 281–294. Det Norske Videnskaps Akademi. I. Matematisk - Naturvitenskapelig Klasse, Skrifter, Ny Serie, Oslo, Sweden.

Steen, R. and Thorsdatter, A. 2011. Portable digital video surveillance system for monitoring ﬂower-visiting bumblebees. Journal of Pollination Ecology, 5:90–94.

Stenstr¨om,M., Gugerli, F., and Henry, G. H. R. 1997. Response of Saxifraga oppositifolia L. to simulated climate change at three contrasting latitudes. Global Change Biology, 3(S1):44–54.

Stenstr¨om,M. and Molau, U. 1992. Reproductive ecology of Saxifraga oppositifolia: phenology, mating system, and reproductive success. Arctic and Alpine Research, 24(4):337–343.

Stocker, T., Qin, D., and Platner, G. 2013. Climate Change 2013: The Phys- ical Science Basis. Working Group I Contribution to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Summary for Policymakers (IPCC, 2013).

Straka, J. 2012. Humming along or buzzing oﬀ? The elusive consequences of plant-pollinator mismatches and factors limiting seed set in the Coast Range of British Columbia. Master’s thesis, University of Victoria.

Strathdee, A. and Bale, J. 1998. Life on the edge: insect ecology in arctic environments. Annual review of entomology, 43(1):85–106.

Svoboda, J. and Freedman, B., editors 1994a. Ecology of a Polar Oasis: Alexandra Fiord, Ellesmere Island, Canada. Captus University Publica- tions, Toronto.

Svoboda, J. and Freedman, B., editors 1994b. Ecology of a Polar Oasis: Alexandra Fiord, Ellesmere Island, Canada, chapter Plant Communities on the Uplands in the Vicinity of the Alexandra Fiord Lowland, pages 97–110. In Svoboda and Freedman (1994a).

Tamura, S. and Kudo, G. 2000. Wind pollination and insect pollination of two temperate willow species, Salix miyabeana and Salix sachalinensis. Plant Ecology, 147(2):185–192.

87 Bibliography

Tape, K., Sturm, M., and Racine, C. 2006. The evidence for shrub expansion in northern Alaska and the Pan-Arctic. Global Change Biology, 12(4):686– 702.

Totland, Ø. 1994. Influence of climate, time of day and season, and flower density on insect flower visitation in alpine Norway. Arctic and Alpine Research, 26(1):66–71.

Totland, Ø. 1996. Flower heliotropism in an alpine population of Ranunculus acris (Ranunculaceae): eﬀects on ﬂower temperature, insect visitation, and seed production. American Journal of Botany, 83(4):452–458.

Totland, Ø. 1999. Eﬀects of temperature on performance and phenotypic selection on plant traits in alpine Ranunculus acris. Oecologia, 120(2):242– 251.

Totland, Ø. and Alatalo, J. M. 2002. Eﬀects of temperature and date of snowmelt on growth, reproduction, and ﬂowering phenology in the arctic/alpine herb, Ranunculus glacialis. Oecologia, 133(2):168–175.

Totland, Ø. and Eide, W. 1999. Environmentally-dependent pollen limitation on seed production in alpine Ranunculus acris. Ecoscience, 6:173–179.

Totland, Ø. and Sottocornola, M. 2001. Pollen limitation of reproductive success in two sympatric alpine willows (Salicaceae) with contrasting pollination strategies. American Journal of Botany, 88(6):1011–1015.

Van der Putten, W. H., Macel, M., and Visser, M. E. 2010. Predicting species distribution and abundance responses to climate change: why it is essential to include biotic interactions across trophic levels. Philosophical Transactions of the Royal Society B: Biological Sciences, 365(1549):2025– 2034.

Wada, N. and Kanda, H. 2000. Notes on ﬂoral traits and gender expres- sion of Dryas octopetala under a simulated environmental change. Polar Bioscience, 13:147–151.

Walker, M., Walker, D., Welker, J., Arft, A., Bardsley, T., Brooks, P., Fahnestock, J., Jones, M., Losleben, M., Parsons, A., et al. 1999. Long-term experimental manipulation of winter snow regime and summer temperature in arctic and alpine tundra. Hydrological Processes, 13(1415):2315–2330.

88 Walker, M. D., Wahren, C. H., Hollister, R. D., Henry, G. H. R., Ahlquist, L., Alatalo, J., Bret-Harte, M., Calef, M., Callaghan, T., Carroll, A., et al. 2006. Plant community responses to experimental warming across the tundra biome. Proceedings of the National Academy of Sciences of the United States of America, 103(5):1342–1346.

Warming, E. 1888. Biologiske optegnelser om gronlandske planter. 3. Scro- phulariaceae. Svensk Botanisk Tidskrift, 17:202–227.

Waser, N. M. and Ollerton, J. 2006. Plant-Pollinator Interactions: From Specialization to Generalization. University of Chicago Press, Chicago.

Welker, J., Fahnestock, J., and Jones, M. 2000. Annual CO2 ﬂux in dry and moist Arctic tundra: ﬁeld responses to increases in summer temperatures and winter snow depth. Climatic Change, 44(1-2):139–150.

Welker, J. M., Molau, U., Parsons, A. N., Robinson, C. H., and Wookey, P. A. 1997. Responses of Dryas octopetala to ITEX environmental manipulations: a synthesis with circumpolar comparisons. Global Change Biology, 3(S1):61–73.

Wookey, P., Robinson, C., Parsons, A., Welker, J., Press, M., Callaghan, T., and Lee, J. 1995. Environmental constraints on the growth, photosynthe- sis and reproductive development of Dryas octopetala at a high Arctic polar semi-desert, Svalbard. Oecologia, 102(4):478–489.

Wookey, P. A., Aerts, R., Bardgett, R. D., Baptist, F., Br˚athen,K. A., Cornelissen, J. H., Gough, L., Hartley, I. P., Hopkins, D. W., Lavorel, S., et al. 2009. Ecosystem feedbacks and cascade processes: understanding their role in the responses of Arctic and alpine ecosystems to environmental change. Global Change Biology, 15(5):1153–1172.

Wookey, P. A., Parsons, A. N., Welker, J. M., Potter, J. A., Callaghan, T. V., Lee, J. A., and Press, M. C. 1993. Comparative responses of phenology and reproductive development to simulated environmental change in Sub- Arctic and High Arctic plants. Oikos, 67(3):490–502.

Yee, T. W. 2013. VGAM: Vector Generalized Linear and Additive Models. R package version 0.9-2.

Zuur, A., Ieno, E., Walker, N., Saveliev, A., and Smith, G. 2009. Mixed eﬀects models and extensions in ecology with R. Springer.

89 Appendix A

Model Fitting

Table A.1: Model parameters used to infer Above-Ground Biomass (AGB). Model Parameters Equation 2.1 (Salix arctica) b0=-5.02, b1=0.82, b2=0.50, b3=0.98 Equation 2.2 (Dryas integrifolia) b0=-3.74, b1=1.39, b2=1.02 Equation 2.3 (Papaver radicatum) b0=-5.02, b1=0.82, b2=0.50, b3=0.98

90 Appendix A. Model Fitting c 0 ∆AIC c AIC 250.73248.50246.47 6.39 246.31 4.16 2.13 179.31 1.97 181.15 0.23 185.47 2.07 184.78138.41 6.39 136.38 5.70 134.57 4.42 135.76 2.39 133.99 0.58 195.40 1.77 220.16 1.11 125.54 2.48 2.48 Flower Number / Biomass 244.34179.08 0 0 194.28217.68 0 123.06 0 0 c ∆AIC c AIC is AIC corrected for ﬁnite sample sizes (Burnham 262.58260.88 5.10 258.71 3.40 259.57 1.23 2.08 185.25184.05 4.85 187.14 3.64 187.28 6.73 156.52 6.88 154.32 3.52 154.99 1.32 165.57 1.99 12.56 192.10 2.64 167.52 2.73 137.74 2.92 Flower Number 257.48180.41 0 0 153.00189.46 0 164.80 0 134.82 0 0 c Model Terms Warming * Pollen Warming + Pollen Warming Pollen - Warming * Pollen Warming + Pollen Warming Pollen - Warming * Pollen Warming + Pollen Warming Pollen - Pollen - Pollen - Pollen - OTC x Pollen OTC x Pollen OTC x Pollen Pollen Pollen Pollen Plant SpeciesSalix arctica Factors Dryas integrifolia Papaver radicatum Salix arctica Dryas integrifolia Papaver radicatum Table A.2: Likelihood criteria forand ﬂower production Anderson, models. 2002). AIC Terms in bold indicate the “best” model.

91 Appendix A. Model Fitting AIC ∆AIC -735.91-737.42-736.23 3.38 -738.09 1.87 -838.02 3.06 -847.46-859.02 1.20 29.89 -856.41 20.44 -509.77 8.89 11.49 -518.86-528.47 29.27 -529.36 20.18 10.58 -622.09 9.69 -743.38 21.44 -354.29 25.81 27.50 Seed mass per Flower -739.29 0 -867.91 0 -539.04-643.53-769.19 0 0 -381.79 0 0 AIC ∆AIC 887.97 3.66 884.31 0 3385.023383.01 4.03 3387.29 2.02 6.30 3385.261739.01 4.28 1737.47 5.49 1735.47 3.95 1735.52 1.95 2.00 1231.361229.32 4.63 1227.22 2.59 1228.76 0.48 2.03 2625.18 25.71 1506.00 0.39 Seed Number 3380.99 0 1733.52 0 1226.732599.48 0 1505.62 0 0 Model Terms Warming * Pollen Warming + Pollen Warming Pollen - Warming * Pollen Warming + Pollen Warming Pollen - Warming * Pollen Warming + Pollen Warming Pollen - Pollen - Pollen - Pollen - OTC x Pollen OTC x Pollen OTC x Pollen Pollen Pollen Pollen Plant SpeciesSalix arctica Factors Dryas integrifolia Papaver radicatum Salix arctica Dryas integrifolia Papaver radicatum Table A.3: Likelihood criteriamodel. for seed production and seed mass models. Terms in bold terms indicate the “best”

92 Appendix A. Model Fitting DIC ∆DIC 755.92 1.34 754.58 0 3932.773933.52 0.38 3934.15 1.13 3933.47 1.75 1.08 4729.094729.30 1.58 4730.46 1.78 4730.86 2.95 3.35 1540.101542.82 0.45 1540.12 3.17 1540.73 0.47 3260.62 1.08 1.12 3213.96 1.84 Germination Rate 3932.39 0 4727.51 0 1539.65 0 3259.513212.12 0 0 AIC ∆AIC -4500.28-4521.90 63.24 -4541.11 41.61 -4544.38 22.40 19.14 -2165.58-2184.89 56.80 -2205.52 37.49 -2201.82 16.86 20.56 -1653.04-1676.02 69.98 -1700.47 46.99 -1698.72 22.54 24.30 -4544.38 19.14 -2084.99 21.08 -1753.24 24.20 Average Seed Mass -4563.51 0 -2222.38 0 -1723.02-4563.51 0 -2106.08 0 -1777.44 0 0 Model Terms Warming * Pollen Warming + Pollen Warming Pollen - Warming * Pollen Warming + Pollen Warming Pollen - Warming * Pollen Warming + Pollen Warming Pollen - Pollen - Pollen - Pollen - OTC x Pollen OTC x Pollen OTC x Pollen Pollen Pollen Pollen Plant SpeciesSalix arctica Factors Dryas integrifolia Papaver radicatum Salix arctica Dryas integrifolia Papaver radicatum Table A.4: Likelihood criteriaMonte for Carlo seed Markov mass Chain and model germination selection. models. Terms DIC in is bold a indicate Bayesian the analogue “best” of model. AIC used in