Abundance and Diversity of pollinators and Orchid in Secondary and Primary forest habitats in East Amazon

Sara Hellström

Master thesis 30 credits

Supervisor: Dr. Yann Clough

Conservation Biology

Dept. of Biology

Faculty of Science

Lund University

2017

Abstract

The Brazil nut tree (Bertholletia excelsa) produces Brazil nuts, an economically important non-timber forest product.

As land-conversion from forest to field increases throughout the Brazil nut tree’s range, many trees end up being the only remaining mature tree in open fields or in secondary forest. The Brazil nut tree is dependent on a variety of large bees for pollination and fruit set. It is therefore essential to investigate how landscape changes affects the tree’s pollination services. In order to see if abundance and composition of the pollinator community differs between degraded, secondary forest and older, continuous forests where Brazil nut is harvested, the Orchid (Euglossinae) community together with other known Brazil nut pollinators were sampled using fragrance baits. Data on average per-tree fruit yield was gathered and compared between landscape types, and production was compared with pollinator abundance. The study suggests that both orchid bee and other Brazil nut pollinator abundance is higher in degraded sites compared to primary forest sites, while richness and composition remains unaffected. This may be due to a spike in pollen and nectar resources following slash-and-burn practices, leading to pollinators being more concentrated in degraded, secondary growth forests close to agricultural fields. There was no correlation between pollinator abundance and production. To further investigate how land conversion and fragmentation affects

Brazil nut pollination services, direct observational studies of pollinators as well as studies on foraging ranges, pollen and nectar resource availability and nest prevalence are warranted.

Contents Introduction ...... 1 Methods ...... 3 Study organisms ...... 3 Study sites ...... 5 Sampling method ...... 7 Per-tree fruit count ...... 8 Statistical analysis ...... 9 Results ...... 10 Orchid bee inventory ...... 10 Brazil nut pollinator abundance ...... 11 Production ...... 12 Discussion ...... 14 Acknowledgements ...... 17 References ...... 18

1

Introduction

The Amazon rainforest has seen large areas subjected to logging and land conversion, leading to biodiversity loss and impacting local and global climate (Ochoa‐Quintero et al., 2015, Barlow et al., 2016). The livelihood of people in rural areas is often dependent on detrimental practices such as logging, clear-cutting for cattle grazing or mining. As an alternative source of income that entails less negative impact on forest ecosystems, collecting so-called Non-Timber Forest Products (NTFPs) are presented as an opportunity (Nepstad and

Schwartzman, 1992, Clay, 1997). These are products such as fruits, nuts, reisins, leaves and bark that can be harvested directly from a mature forest without felling trees. For this reason, there has been an increased interest in promoting these products on international markets in order to provide a non-destructive means of income to forest holders. However, its long-term economic viability in the face of rapid modernization and global market fluctuations has been questioned (Terborgh and Peres, 2017, Arnold and Pérez, 2001). Nevertheless, as forest degradation increases, it is of great importance to investigate how this affects the productivity of NTFP species in order to guide optimal harvesting and management practices.

One of the most economically important NTFPs in the Amazon region is Brazil nuts. The Brazil nut tree

(Bertholletia excelsa Humboldt & Bomplant) is a signature species of the Amazon rainforest, often towering above the surrounding canopy. The edible seeds have been a food source for humans in the Amazon basin since prehistoric times, and there are indications of humans playing a role in dispersing the tree to its current range (Shepard and

Ramirez, 2011). Today, the Brazil nut tree can be found in lowland tropical humid forest from eastern Brazil to the

Andes in the west. The seed (called Brazil nut, Para nut, Amazon nut or castaña) is an important export product for

Peru, Bolivia and Brazil, as well as a locally traded commodity providing a supplementary income for small-time farmers (Coslovsky, 2014). The majority of nuts are harvested directly from wild trees, making it a prime example of a NTFP (Clay, 1997). The long-term economic value to forest owners has made it a subject of much legislation, and the trees are legally protected in Brazil, Bolivia and Peru (Guariguata et al., 2010, Cronkleton et al., 2012). Timber extraction, both legal and illegal, is an integral part of forest use in most areas where Brazil nut harvesting takes place, and it has been shown that selective logging can be combined with Brazil nut harvesting without significant productivity loss (Rockwell et al., 2015) nor decreased sapling regeneration (Soriano et al., 2012). However, since

Brazil nut trees are legally protected, they are often the only mature trees left after the rest of the forest has been logged or burned in favor of agriculture or cattle farming. Little research has been done on how these trees fare in 2 highly disturbed, fragmented landscapes. The Brazil nut tree is self-sterile, and fruit set is dependent on pollination by large bees. For pollinator-dependent species, isolation and fragmented populations will lead to reduced seed set due to pollen limitation (Ghazoul, 2005). Thus, for trees left in a fragmented landscape, the pollination services necessary for fruit set might be under threat.

Neotropical bees populations tied to forest habitats are most likely affected by deforestation and agricultural intensification, though lack of knowledge on range, food sources and life cycle traits makes predictions difficult for many species (Freitas et al., 2009). In tropical regions, 98% of plant species are dependent on pollination

(Ollerton et al., 2011) including most crop species. Yield is positively related to native wild bee species richness and abundance for important crops such as coffee (Klein et al., 2003), cashew (Freitas B. M. et al., 2014), and passion fruit (Yamamoto et al., 2012). Habitat fragmentation following deforestation threatens pollination services for many plant species, leading to decreased pollen deposit and fruit set (Rocha and Aguilar, 2001, Cunningham, 2000,

Ghazoul, 2005) as well as increased inbreeding frequencies (Lamont et al., 1993). Since the Brazil nut tree has very large and heavy seed pods that rarely get dispersed over long distances, clustered groups of trees are predicted to be related (Mori and Prance, 1990). For this reason, pollinators capable of traveling long distances are essential for genetic mixing. A key family of pollinators for Brazil nut and many other low-density plant species in tropical environment are orchid bees (Euglossinae). They are capable of flying long distances, and regularly visit the same resources within their home range, making them important vectors for long-distance gene transfer (Janzen, 1971,

Wikelski et al., 2010). A decrease in pollinator abundance and mobility could lead to lower rates of cross-individual pollen deposits, increasing inbreeding frequencies and thus pose a threat to the short-term productivity and long- term regeneration capabilities of Brazil nut trees.

In this study I investigate if there is a difference in pollinator abundance and diversity between degraded secondary forest and closed-canopy primary forest where Brazil nut is harvested from wild populations. I will focus on orchid bees (Euglossinae), together with other previously known Brazil nut pollinators.

Aims of this study are as follows:

i. To test if abundance, diversity and species composition of orchid bee males differ between degraded,

secondary forest and closed canopy primary forest.

ii. To test if abundance of known Brazil nut pollinators differs between degraded, secondary forest and closed

canopy primary forest. 3

iii. To see if pollinator abundance can be correlated with per-tree Brazil nut yield.

Methods

Study organisms

Brazil nut tree (B. excelsa) - The Brazil nut tree belongs to the neotropical family Lecythidaceae. It is an imposing tree, reaching up to 50 meters in height (Mori and Prance, 1990). It grows in terra firme forests with wet and dry seasonal pattern and flowers for extended periods during rainy season. Brazil nut trees are mainly allogamous, self- incompatible, and are dependent on vectors for pollination and seed dispersal. It has a patchy distribution with an average density of 1.3 trees per ha in what is considered Brazil nut-rich forest (Wadt et al., 2005, Peres and

Baider, 1997), sometimes distributed evenly (Wadt et al., 2005), but more often concentrated in groves of 50-100 trees, separated by up to a 1000 meters (Mori and Prance, 1990, Peres and Baider, 1997). The seeds grow within hard-cased round pods, “cocos”, that are dispersed over short distances (5-20 meters) by large rodents called agoutis

(Dasyprocta spp.)(Peres and Baider, 1997). Flowers grow in large clusters on terminal panicles, where each flower remains open for a few hours at dawn before dehiscing and dropping to the ground on the same day (Mori et al.,

1978). The flowers are zygomorphic with an inwards bending ligule, requiring a large-bodied bee to land on and fully enter the flower in order for pollination to occur (Maués, 2002, Cavalcante et al., 2012). Rewards consist of nectar and pollen. In observational studies based in plantations, it has been shown that large bees of the genera

Xylocopa, Centris, , Epicharis, Eufreisea and Bombus provide the vast majority of pollination services, though other families might harvest nectar from the flowers (Table 1.) (Nelson et al., 1985, Cavalcante et al., 2012,

Maués, 2002, Santos and Absy, 2010).

4

Table 1. All observed Brazil nut pollinators from plantation-based studies in Acre, Manaus and Amazonia states,

Brazil. Significant contributors to pollen deposition in bold. (Nelson et al., 1985, Cavalcante et al., 2012, Maués,

2002, Santos and Absy, 2010).

Tribe Species Tribe Species Bombini Bombus brevivillus Epicharis rustica Bombus transversalis Epicharis zonata Centridini Centris americana Euglossinae Eufriesea flaviventris Centris denudans Eufriesea purpurata Centris carrikeri Euglossa ignita Centris ferruginea Eulaema mocsaryi Centris dimidiata Centris flavifrons Eulaema bombiformis Centris flavilabris Eulaema cingulata Centris similis Eulaema nigrita Epicharis conica Xylocopini Xylocopa frontalis Epicharis flava Xylocopa aurulenta Epicharis umbraculata Xylocopa muscaria Epicharis affinis

Orchid bees (Euglossinae), - A diverse group of bees exclusive to the neotropics, occurring from southern Brazil to

Mexico. They are characterized by their very long tounge and often striking metallic coloration. The family contains five genera: Euglossa, Eulaema, Eufriesia and two parasitic genera Exaerete and Aglae. Euglossine bees are the primary pollinators of many orchid species, and among the most important pollinators in tropical forest ecosystems because of their ability to disperse pollen over long distances (Williams and Dodson, 1972, Janzen, 1971). A large number of orchid species are exclusively dependent on pollination by orchid bees (Ackerman, 1983a). Several species of the orchid bee genus Eulaema have been observed to be important pollinators of Brazil nut trees in plantations (Cavalcante et al., 2012, Maués, 2002, Santos and Absy, 2010). They are known to travel long distances

(5-10 km daily), making them important pollen vectors for plant species with patchy or widely spaced distribution

(Janzen, 1971). One particular trait that has simplified the study of this family is the tendency of males to be selectively attracted to certain aromatic compounds. In fact, many orchid species offer only scents as a reward instead of nectar or pollen. The odorous substances are stored in a special organ the hind tibia of male euglossine

(Adams, 1968), and are most likely used in courtship. Since the discovery of this phenomenon, many studies using scent baits have been performed concerning the seasonality abundance and diversity of this genera all over the neotropics (Janzen D. H. , 1982, Ackerman, 1983b, Dressler, 1985, Roubik and Ackerman, 1987, Armbruster, 1993, 5

Sandino, 2003, Rocha-Filho and Garofalo, 2014, Nemesio and Rasmussen, 2014, Knoll, 2016), leading to the discovery of many new species. This methodology can also be used to investigating the effects of landscape change and how it affects pollination networks, especially in tropical forests were direct observational studies of pollination can be complicated due to stratification and landscape complexity. The abundance of males have been shown to respond differently to forest degradation, sometimes appearing more abundant in small forest fragments (Becker,

1991, Rasmussen, 2009) or decreasing with level of human intervention (Oliveira and Campos, 1995).

Xylocopa frontalis (Olivier 1789)– A very large solitary bee of the family carpenter bees (Xylocopinae). X. frontalis is present in all of Amazonia and is an important pollinator for crops such as passion fruit (Yamamoto et al.,

2012). It nests in burrows chewed out of dead hardwood. Semi-social behavior can be observed among females(Camillo and Garófalo, 1989, Michener, 2000). It has been named the most important Brazil nut pollinator in terms of number of flower visitors and pollen load per visits in central Amazonian plantation-based studies.

Bombus transversalis – (Olivier 1789) The only species of bumble bee present in the Amazon basin. It forms subterranean colonies on the forest floor in terra firme humid forests with up to 400 adult individuals recorded

(Olesen, 1989, Taylor and Cameron, 2003).

Study sites

The study area was located in Loero and Jorge Chavez districts at the border of the Tambopata National Reserve,

Madre de Dios province, Peru. The area has tropical monsoon climate with distinct dry and wet seasonal pattern

(Köpper climate classification system). Mean annual temperature is 24.5 C and average annual rainfall is 2200-2500 mm (Climate-data.org, 2017). In Madre de Dios, 30% of the standing forest is considered Brazil nut-rich forests. The buffer zone of the Tambopata National Reserve is a mosaic of agricultural fields, cattle grazing grounds and forest fragments, bordering the Tambopata river. It is populated by farmer families whose main sustenance besides Brazil nut harvesting is yucca and papaya cultivation. Three of the study sites were located in the Tambopata National

Reserve, where Brazil nut harvesting is also permitted. Two forest types were investigated: secondary forest (purma:

P), consisting of 2-10 year old secondary forest on previously burned ground, in close proximity (max 50 m) to fields of yucca or papaya, and closed canopy forest (monte alto: M), were no disturbance such as burning or clear cutting 6 had taken place, although all sites were to some extent subjected to selective logging in the past. Each degraded site was coupled to a mature forest site nearby to prevent too much variation in factors like soil and forest type (Figure

1,2). Distance between paired sites ranged from 600-4000 m. To minimize edge effects, minimum distance from forest edge to sampling point for mature forest sites was 300 m. A total of eight sites in four pairs were selected as study sites for a larger research project on Brazil nut productivity.

Figure 1. Study site configuration and land-use map. First letter indicates pairing. Second letter indicates site type. M:“Monte”, closed-canopy continuous forest sites. P: “Purma”,secondary forest sites. (Map courtesy of D. Navarro-Perez, reproduced with permission). 7

Figure 2. Study point locations on a satelite image (Google, 2017)

Sampling method

In each study site, one study point was set up within 20 m radius from one of the Brazil nut trees previously selected for productivity measures. Study points were located as close as possible to the middle of the study site, where a suitable clearing could be found. Sampling was conducted for a total of 16 days between March 15th and April 18th,

2017. Each site was sampled in 3 hour blocks between 7.30 am and 11.30 am on two occasions, combining to a total sampling effort of 6 hours per site, since male activity is said to peak between 7-12 am (Ackerman,

1983b). Sampling was only initiated on days without rain, and was discontinued if there was persistent rain for more than ten minutes.

Euglossine males were attracted with the well-tested method of using scent baits (Adams, 1968, Ricklefs et al.,

1969). Three volatile fragrances were used: vanilin, eucalyptol (1,8-Cineole) and eugenol. According to Pearson &

Dressler (1985), the most attractive baits also include benzyl acetate and methyl salicylate, both of which I was unable to attain during the designated sampling period. One ml of each volatile was poured onto a cotton swab and hung with a cotton string 1.5 m above the ground, approximately 3 m apart. All euglossine males approaching the 8 baits were collected with a hand net. Larger species that were easily identified in the field were released after sampling had been terminated to avoid duplicates. Smaller males were collected and identified using various keys

(Bonilla-Gómez and Nates-Parra, 1992, Dressler, 1978, Dressler, 1984, Michener, 2000). All previously known

Brazil nut pollinators, active within a ten meter radius from the baiting station, were counted during the sampling hours regardless if they approached the baits or not. This included males and females of Xylocopa frontalis, Bombus transversalis and females of Eulaema spp.

Figure 3. Photo examples of Brazil nut trees growing in secondary forest sites (degraded, Purma) and closed canopy forest (primary, Monte).

Per-tree fruit count

In line with previous studies on Brazil nut productivity (Rockwell et al., 2015), fruit count (as opposed to seed count) was chosen an estimator of productivity. In each site, all Brazil nut trees were examined for suitability. Trees with 9 low liana load, entire crown and a DBH of >80 cm were considered for the study. Only trees 30 meters or more from its closest neighbor were chosen, to not risk mixing of fruits. From this pool, all suitable trees in a secondary forest was selected, and matched with a similar number trees selected at random from paired closed canopy forest site, ranging from 9-17 trees per site. All empty shells from the latest dropping season were counted. If there were any doubts about which cocos belonged to wich tree, or if fruits had been removed, the tree was excluded from further studies.

Statistical analysis

A linear mixed-effects model (Bates et al., 2014) was used to test for difference in abundance and species richness between forest types with site pairs as a nested factor, using a Likelihood-Ratio test to compare against a null model.

This was performed for all orchid bee males separately, and for all known Brazil nut pollinators. The species

El.cingulata, El.mocsaryi and El.meriana were included in both these data sets. Shannon-Wiener diversity index and evenness was calculated and compared in a similar mixed-effects model for the two forest types. Chao1 diversity estimate was used to compare predicted number of species for the two landscape types (Chao, 1984). For each landscape type, rank-abundance curves were calculated using R package Vegan (Oksanen et al., 2013). Jaccard index of similarity was used to compare paired sites. Per-tree yield was log-transformed and tested against pollinator abundance using Pearson correlation. All analyses were performed using R version 3.3.1 (REF).

10

Results

Orchid bee inventory

A total of 588 males of 19 species of Orchid bees of the genera Euglossa, Eulaema and Exaerete were recorded (Table 1.), representing nearly half of the 39 species known to be present in the Tambopata reserve

(Dressler 1985). The most common species in both habitats was Euglossa imperialis representing 45% of total catch. Eg. periviridis and Eg. singularis were both unique to degraded sites, but represented by one individual each.

The only species unique to the forest sites were Eg. townsendii, represented by two individuals.

Table 2. All species and individuals per site.

Species Forest sites Degraded sites Total MA MB MC MD PA PB PC PD Bombus transversalis 1 4 3 3 11 Euglossa bidentata 1 2 1 1 1 2 8 Euglossa allosticta 1 4 1 6 Euglossa amazonica 1 3 3 8 4 15 34 Euglossa augaspis 2 2 3 1 8 Euglossa chalybeata 5 6 13 3 1 6 1 35 Euglossa ignita 2 1 1 1 2 1 3 11 Euglossa imperialis 21 18 40 56 8 31 32 28 234 Euglossa intersecta 2 4 7 1 4 6 4 28 Euglossa modestior 6 1 2 6 5 1 4 25 Euglossa mourei 5 1 5 8 10 9 38 Euglossa periviridis 1 1 Euglossa securigea 1 2 1 2 5 5 14 30 Euglossa singularis 1 1 Euglossa sp. 1 4 1 6 Euglossa townsendii 2 2 Eulaema cingulata 5 4 18 1 19 15 31 93 Eulaema meriana 2 1 2 2 6 3 16 Eulaema mocsaryi 1 3 1 1 6 Exaerete frontalis 1 1 2 4 Exaerete smaragdina 1 3 1 3 8 Xylocopa frontalis 1 45 7 2 55 Total 40 55 71 94 83 107 87 123 660

Site type affected abundance (χ² (1)= 4.81, p=0.0283*), but not species richness (χ²(1)=1.41, p=0.2355), with degraded sites having slightly higher abundance (slope= 21.75 ±SD 8.2) (Table 3.). Site type did not significantly affect species richness, nor was there a correlation between abundance and species richness (p=0.2801). Jaccard similarity index suggests high likeness between landscape types among paired sites (0.8-0.6).

Table 3. Results from mixed-effect models 11

χ² DoF p Abundance Euglossinae 4.8097 1 0.0283 * Species richness 1.4071 1 0.2355 Abundance pollinators 7.856 1 0.0051 ** Diversity (H') 9.377 1 0.0022 * Eveness 5.613 1 0.0178 *

Shannon-Wienner diversity index (H’) was significantly higher in degraded sites (χ²(1)=9.377, p=0.002**).

Degraded sites also scored higher for evenness (J) (χ²(1)=5.613, p=0.0178*). Chao1 species richness estimates extrapolates a similar number of unseen species in both landscape types: 19 degraded sites (+2) and 21 for primary forest sites (+2).

Figure 4. Rank-abundance curves for primary forest sites (Monte) and secondary forest sites (Purma) showing names on the four most common species .

Brazil nut pollinator abundance

In total, five known species of pollinators of B. excelsa was encountered during the survey: Xylocopa frontalis,

Eulaema cingulata, Eulaema mocsaryi, Eulaema meriana and Bombus transversalis. Abundance of pollinators was significantly higher in degraded sites (χ2(1)= 7.86, p=0.0051**). Of the X. frontalis encountered, 45 individuals occurred in the same site. With this outlier removed, pollinator abundance was still significantly higher in degraded 12 sites (χ2(1)= 7.06, p=0.0079 **). The most common occurrence was El. cingulata, which was present in all sites but one, and significantly more abundant in degraded sites (χ2(1)=6.0711, p=0.01374 *).

Production

Of the 20 most productive trees, 14 occurred in degraded sites. Number of fruits per tree ranged from 0 to 800, and was varible between sites (Figure 5). There was no correlation between pollinator abundance and mean per-tree fruit

count per site (R2= 0.08462) (Figure 6).

800

600

400

Total nr of fruit of nr Total

200 0

AM AP BM BP CM CP DM DP

Site

Figure 5. Boxplot showing distribution of per-tree fruit production per site. First letter indicates pairing. Second letter indicates site type. M:“Monte”, closed-canopy continuous forest sites. P: “Purma”,secondary forest sites. 13

Figure 6. Graph illustrating non-significnt correlation between mean fruits per tree (dependent, ln-transformed) and pollinator abundance (independent) Circle indicates primary forest site “Monte” s and squares indicate secondary forest sites “Purma” (R2 = 0.08462)

14

Discussion

Orchid bee inventory - The study suggests that euglossine as well as pollinator abundance is higher in degraded, secondary forest sites compared to continuos, primary forest sites, though the species assemblages between the two landscape types was similar. A similar result has been obtained in some cases in previous studies on euglossine abundance along a disturbance gradient (Becker, 1991, Rasmussen, 2009). Sandino and Otero (2003) found abundance to be significantly greater in degraded farmland, compared to both secondary and primary forest.

The oposite result was found by Oliveira and Campos (1995), where abundance increased with forest fragment size.

Powell and Powell (1987) showed that Eulaema cingulata, El. meriana and El. bombiformis, wich are

Brazil nut pollinators, were more numerous in small forest framents and clearings. The result was replicated in this study for Eulaema cingulata and El. meriana, wich were both more abundant in degraded sites. Roubik (1993) found a tendency for larger Euglossine bees such as Eulaema sp. to be more frequent at canopy height than smaller

Euglossinae. He relates this to a greater capacity for heat loss during flight, which may also influence these bee’s capacity to forage in more open, drier habitat, such as the degraded sites in our study. If this theory holds true, larger species that are also important Brazil nut pollinators might be better adapted to life in disturbed habitats, which seems to hold true for several species of Eulaema (Sandino, 2003). Nevertheless, these species, as well as all other orchid bees, need a large number of flowers such as epiphytic orchids in order to gather fragrances and attract a mate. It is therefore reasonable to assume that orchid bee populations are tied to forest habitats, and will decrease in abundance with distance from continuous forest where a large source population could reproduce. This could be further investigated by examining a gradient of landscapes further from the continuous forest.

The distance between our paired sites were also withtin the potential flight ranges of orchid bees, wich can have foraging ranges of 5+ km (Janzen, 1971). Thus, the population we encounter in secondary forest or in degraded landscapes might still be sourced from the primary, continuos forest habitat. The similarity in species composition between site types further support this claim.

Our most common species was Euglossa imperialis, which is normally one of the most abundant species found in humid forests (Roubik and Ackerman, 1987). Populations in central American have previously been shown to contain a large number of haploid, infertile males (Zayed et al., 2004). If this were to be true for populations in

Amazonia, the effective population size could be smaller than what is observed in censuses of this kind. This might have particular implications for fragmented landscapes were isolation could lead to less genetic mixing, in turn 15 leading to more infertile males, shrinking the effective population size while maintaining the same number of individuals. The authors suggests that haploid male frequency as a more effective measure of pollinator decline, therefore it would be of interest for future researches to genetically study target species in relation to forest fragmentation.

Brazil nut pollinator inventory - Along with the three species of Eulaema previously discussed, the significant Brazil nut pollinator Xylocopa frontalis and Bombus transversalis were found. They both occured almost exclusively in secondary forest sites. The occurrence of X. frontalis was patchy, with mostly occasional sightings of females. In one degraded site with very little shade, surrounded by yucca plantations and various species of weeds, we encountered a “lek” of X. frontalis were a large number of males and females gathered, males apparently fighting for territory and mate access. Some females even landed on out vanillin baits. In the first visit we observed 9 males and 10 females. Two weeks later we observed 4 males and 22 females, indicating that this site was supporting a large concentration of bees for an extended period of time. This behavior is caused by males releasing a pheromone from special glands in the abdomen. X. frontalis is classified as performing non-resource defending male mating displays

(Leys and Hogendoorn, 2008). This indicates that the individuals encountered were not using this particular site because of resource richness or proximity to nesting sites, but as an arbitrary arena for male display.

One specimen of Acanthopus palmatus, nest parasite of Centris (Ptilotopos) (Rozen and Buchmann, 1990), was found in one of the forest sites. The specimen was caught entering what was presumably a Centris nest constructed in a disused arboreal termite nest on the trunk of a Brazil nut tree.

Implications for Brazil nut productivity - In our study, many trees in disturbed sites we recorded to have high fruit production compared to undisturbed sites, as has previously been shown in other studies (Cascante et al., 2002), although it is important to note that inter-annual production per tree is variable (Rockwell et al., 2015). In an unpublished study using the same productin data presented here, there is a trend towards degraded sites having higher yield (Jansen, 2017). Both DBH and crown diameter are more variable withtin sites than between landscape types, and both are strong predictors of productivity (Rockwell et al., 2015). Allthough mean fruit yield and pollinator abundance was not correlated in this study, the perceived higher abundance of pollinators in secondary forest this could indicate a case of “reproductive 16 dominance” of trees in degraded sites (Aldrich and Hamrick, 1998). This means that pollinators drawn to degraded aeas by nectar-rich secondary growth and annual weeds, will more frequently visit trees that remain in those areas, thus concentrating pollination services in these areas while simultaniously disrupting pollination services in nearby forests. There were a large number of annual weeds growing in the clearings created by slash-and-burn and along the field margings, some of these plants could be substantial nectar or pollen resources. To further investigate if these resources are indeed more plentiful in degraded areas, one could perform a number of ground cover studies using the same sites provided in this study. According to Nelson et al. (1985), pollinators visiting Brazil nut trees carried pollen mainly from secondary weeds, indicating that primary forest might not be neccessary to support pollination services.

Another important aspect to consider is the lifetime productivity of free-standing Brazil nut trees. No research has been done on how solitary trees fare over their lifespan, although anecdotal evidence suggests that the trees does not survive for long under conditions, possibly due to increased sun exposure of the surrounding soil, root and trunk damage by fire or disturbance in nutrient cycling. Many of these highly exposed Brazil nut trees occurred in our study area. As this data suggests, a lack of suitable pollinators might not be the largest concerns for these trees.

Suggestions for further studies - This study could be seen as a precursor to a longer, more elaborate monitoring of pollinator populations in degraded areas. Firstly, more fragrances should be included to better reflect local diversity. Pearson & Dressler (1985) found 39 species of males at their bating stations at a nearby locality under a two-year period, compared to 19 species in this study. This included some of the known Brazil nut pollinators such as Eulaema bombiformis and Eufriesia sp that could be present in our study sites, but went unnoticed because we lacked the right bait fragrance. As was suggested by Pearson & Dressler (1985), benzyl acetate and methyl salicylate should be added, along with skatole (Nemesio and Rasmussen, 2014). According to Roubik

(2004) there may not be an overall advantage of increasing the number of sampling days to achieve a more complete species inventory, since even rapid assesments from a few days may yield up to two thirds of known species. Based on seasonality patterns of bee species occurences and with regards to the seasonality of Brazil nut flowering events, I would suggest three one-day samples performed over a year: one in December at the onset of the rainy season, one in march at the start of the dry season, and one in june, the driest month. With the use of additional chemicals, this 17 would provide a more complete picture of the euglossine community in both habitat types as well as additional info on key pollinators.

There are currently no established methods for surveying large tropical bees such as Xylocopa and Centris, but one could test trap-nest coonization rates (Gazola and Garófalo, 2009), but this method requires long periods of surveying. Scent bait surveys for euglossini has the advantage of being practical and time-efficient in a complex environment, but it is not without flaws. The most obvious disadvantage is that one extrapolates female abundance from that of males, which might not be that simply relatable. It is reasonable to believe that there are differences in level of attraction to baits between species, making the relative abundance of some species appear greater or smaller than they really are, while also excluding some less common species completely. For a complete description of difficulties, see Nemesio (2012).

In order to determine the actual foraging ranges, and thus the most likely distance at wich gene flow between individual trees could occur, radio tracking studies of individual bees has great potential. Wikelski et al.

(2010) performed a study on Exaerete individuals, sucsessfully determining several individual’s flight patterns. This might give a better estimate of effective maximum flight range compared to homing experiments, that often over- estimates flight ranges. Brazil nut trees produce significant amounts of pollen during an extended period, making it an important food source during several months. In order to understans how important prazil nut pollen is for significant pollination service providers such as X. frontalis, and to study what food sources it uses during the rest of the year, one could study pollen content of nests or on individuals, as did Nelson (1985).

Since the plantation studies from different areas of the Amazon have found a variation of species to be the most numerous flower visitor, one can assume considerable regional variation in what species is most important

Brazil nut pollinator. For this reason, direct observational studies using canopy platforms (Cavalcante et al., 2012,

Maués, 2002) or camera traps would be warranted in south-eastern Peru and the surrounding region, were Brazil nut production is of great significance for local income.

Acknowledgements

Dr. Merel Jansen for initiating, coordinating and supervising the project, Daniel Navarro-Perez & Eriks Arroyo

Quispe for coordinating field work and making it all practically possible, Consessionarios of Jorge Chavez and Loero 18 districts for allowing the study to take place on their consessions, Universidad Nacional Amazónica de Madre de

Dios (UNAMAD) for generous use of lab equipment, Park rangers of The Tambopata National Reserve for collaboration, Fidel Chiriboga for advice. Project was partially funded by SIDA through a minor field study grant.

Note that site selection, collection and treatment of production data is designed by researchers within the project

SUSTAIN, funded by ETH Zürich, and I do in no way take credit for this. All data presented in this thesis is as of

June 2017 unpublished and used with permission from the responsible researchers.

References

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