Kaiser-Bunbury, C N; Memmott, J; Müller, C B (2009). Community structure of pollination webs of Mauritian heathland habitats. Perspectives in Plant Ecology, Evolution and Systematics, 11(4):241-254. Postprint available at: http://www.zora.uzh.ch University of Zurich Posted at the Zurich Open Repository and Archive, University of Zurich. Zurich Open Repository and Archive http://www.zora.uzh.ch Originally published at: Perspectives in Plant Ecology, Evolution and Systematics 2009, 11(4):241-254.
Winterthurerstr. 190 CH-8057 Zurich http://www.zora.uzh.ch
Year: 2009
Community structure of pollination webs of Mauritian heathland habitats
Kaiser-Bunbury, C N; Memmott, J; Müller, C B
Kaiser-Bunbury, C N; Memmott, J; Müller, C B (2009). Community structure of pollination webs of Mauritian heathland habitats. Perspectives in Plant Ecology, Evolution and Systematics, 11(4):241-254. Postprint available at: http://www.zora.uzh.ch
Posted at the Zurich Open Repository and Archive, University of Zurich. http://www.zora.uzh.ch
Originally published at: Perspectives in Plant Ecology, Evolution and Systematics 2009, 11(4):241-254. Community structure of pollination webs of Mauritian heathland habitats
Abstract
Pollination webs have recently deepened our understanding of complex ecosystem functions and the susceptibility of biotic networks to anthropogenic disturbances. Extensive mutualistic networks from tropical species-rich communities, however, are extremely scarce. We present fully quantitative pollination webs of two plant-pollinator communities of natural heathland sites, one of which was in the process of being restored, on the oceanic island of Mauritius. The web interaction data cover a full flowering season from September 2003 to March 2004 and include all flowering plant and their pollinator species. Pollination webs at both sites were dominated by a few super-abundant, disproportionately well-connected species, and many rare and specialised species. The webs differed greatly in size, reflecting higher plant and pollinator species richness and abundance at the restored site. About one fifth of plant specie at the smaller community received <3 visits. The main pollinators were insects from diverse taxonomic groups, while the few vertebrate pollinator species were abundant and highly linked. The difference in plant community composition between sites appeared to strongly affect the associated pollinator community and interactions with native plant species. Low visitation rate to introduced plant species suggested little indirect competition for pollinators with native plant species. Overall, our results indicated that the community structure was highly complex in comparison to temperate heathland communities. We discuss the observed differences in plant linkage and pollinator diversity and abundance between the sites with respect to habitat restoration management and its influence on pollination web structure and complexity. For habitat restoration to be successful in the longterm, practitioners should aim to maintain structural diversity to support a species-rich and abundant pollinator assemblage which ensures native plant reproduction. * Manuscript
LRH: Kaiser-Bunbury, Memmott, and Müller
RRH: Pollination webs of Mauritian heathland
Community structure of pollination webs of Mauritian heathland habitats
Christopher N. Kaiser-Bunbury1,3, Jane Memmott2 and Christine B. Müller1†
1 Institute of Environmental Sciences, University of Zurich, Winterthurerstrasse 190,
CH–8057 Zurich, Switzerland
2 School of Biological Sciences, University of Bristol, Woodland Road, Bristol, BS8
1UG, UK
3 Corresponding author; Current address: Ecosystem Management, Institute for
Terrestrial Ecosystems, Swiss Federal Institute of Technology (ETH) Zurich,
Universitätstrasse 16, 8092 Zurich, Switzerland
Phone: 0041 44 632 89 45
Fax: 0041 44 632 15 75
e-mail: [email protected]
† deceased 7 March 2008
1 ABSTRACT
Pollination webs have recently deepened our understanding of complex
ecosystem functions and the susceptibility of biotic networks to anthropogenic
disturbances. Extensive mutualistic networks from tropical species-rich communities,
5 however, are extremely scarce. We present fully quantitative pollination webs of two
plant–pollinator communities of natural heathland sites, one of which was in the
process of being restored, on the oceanic island of Mauritius. The web interaction data
cover a full flowering season from September 2003 to March 2004 and include all
flowering plant and their pollinator species. Pollination webs at both sites were
10 dominated by a few super-abundant, disproportionately well-connected species, and
many rare and specialised species. The webs differed greatly in size; reflecting higher
plant and pollinator species richness and abundance at the restored site. About one
fifth of plant species at the smaller community received < 3 visits. The main
pollinators were insects from diverse taxonomic groups, while the few vertebrate
15 pollinator species were abundant and highly linked. The difference in plant
community composition between sites appeared to strongly affect the associated
pollinator community and interactions with native plant species. Low visitation rate to
introduced plant species suggested little indirect competition for pollinators with
native plant species. Overall, our results indicated that the community structure was
20 highly complex in comparison to temperate heathland communities. We discuss the
observed differences in plant linkage and pollinator diversity and abundance between
the sites with respect to habitat restoration management and its influence on
pollination web structure and complexity. For habitat restoration to be successful in
the long-term, practitioners should aim to maintain structural diversity to support a
2 species-rich and abundant pollinator assemblage which ensures native plant
reproduction.
Key words: restoration; oceanic island; complex mutualistic network; alien
5 invasive species; plant–animal interaction
3 INTRODUCTION
The majority of flowering plant species rely on interactions with pollinators
for reproduction, while flower visitors benefit from these interactions by obtaining
food in the form of pollen or nectar. Such mutualistic relationships are rarely mutually
5 exclusive, but flowering plants interact often with a range of pollinator taxa,
suggesting that generalisation is the dominant feature of most pollination systems
(Moldenke, 1975; Waser, et al., 1996; but see Johnson and Steiner, 2000, 2003;
Blüthgen, et al., 2007). Such community-wide patterns in plant–pollinator networks
can be explored through the application of a food web approach (Memmott, 1999;
10 Dicks, et al., 2002; Olesen and Jordano, 2002), which provides important information
on ecosystem stability (Bascompte, et al., 2006), the consequences of disturbance (e.g.
extinctions; Memmott, et al., 2004), the restoration of degraded ecosystems (Hobbs
and Norton, 1996; Montalvo, et al., 1997) and the role of introduced species in such
ecosystems (e.g. Olesen et al., 2002; Morales and Aizen, 2006; Lopezaraiza-Mikel et
15 al., 2007; Aizen et al., 2008; Bartomeus et al., 2008). While food webs traditionally
describe predator-prey interactions, they can also be used to study networks of
mutualistic interactions, such as pollination, where food is ‘traded’ for ‘services’
(Jordano, 1987). Community structure can be characterised by standard food web
statistics such as the mean number of links of each interaction partner in a network
20 (linkage; Paine, 1980) and the ratio of observed to possible interactions in a networks
(connectance; Martinez, 1992), and visualised in quantitative flower visitation webs
(hereafter referred to as pollination webs; cf. Memmott, 1999). Such webs provide
complex yet tractable depictions of species richness and evenness (relative
abundance), interaction frequency, and ecosystem structure and function.
4 Despite recent advances in the analysis of pollination webs, most webs
describe temperate, arctic or high altitude habitats, largely due to practical constraints.
Tropical and subtropical plant–pollinator communities are often extremely species-
rich, and as a result, constructing networks describing entire assemblages remain a
5 considerable challenge. Consequently, most pollination studies in diverse ecosystems
have focused on subsets of communities such as taxonomic groups of pollinators, or
phenologically or spatially restricted plant species (e.g. Kanstrup and Olesen, 2000;
Kato and Kawakita, 2004). A few comprehensive studies have compiled data on the
reproductive biology of most flowering plant species within a tropical or subtropical
10 forest community (Percival, 1974; Kato, 1996; Momose, et al., 1998; Kato, 2000).
However, these studies primarily report qualitative information on species diversity,
community composition and flowering phenology. To make use of the more
comprehensive community web approach, quantitative data on visitation frequency
within well-defined spatial boundaries are required. In this study, we present two fully
15 quantitative pollination webs of entire flowering plant communities on the oceanic
island of Mauritius with the aim of investigating the structure and function of tropical
plant–pollinator interactions at the community level.
The vast majority of island ecosystems have undergone multiple species
extinctions and introductions (e.g. Simberloff, 1986, 1995; Cheke, 1987; Whittaker,
20 1998). Resident mutualistic associations, such as pollination, are likely to be affected
by both the loss of biodiversity and the presence of alien species (Kearns, et al., 1998;
Ghazoul, 2004; Traveset and Richardson, 2006). Quantitative pollination webs are an
ideal tool for understanding the effect of such changes in a community setting. Shifts
in interaction frequency or pair-wise dependency caused by the arrival of alien species
25 and their consequences may only be fully understood within the wider network of
5 interactions. Pollination webs are starting to be used to explore the impact of
introduced species on native mutualistic associations (e.g. Memmott and Waser,
2002; Olesen, et al., 2002, Morales and Aizen, 2006), and some used a fully
quantitative approach to explore community-wide patterns of plant and animal
5 invasion (Lopezaraiza-Mikel, et al., 2007; Aizen, et al., 2008).
In Mauritius, only about 2% of the island is covered with native forest which
is itself heavily degraded (J. Mauremootoo, pers. comm.). In situ restoration of
degraded habitats in Mauritius consists primarily of hand-weeding introduced plant
species in plots across a range of different habitat types. Over the past 20 years the
10 weeding has resulted in a gradual regeneration of native flora within restored plots.
However, there is little information on whether the pollinator community has also
been restored, which is essential if the restoration is to be sustainable. We compiled
and compared quantitative pollination webs of two communities, one managed site
where restoration is in progress and one heavily degraded, unrestored site. The
15 objective of this study was to characterise the structure of two complete tropical plant-
pollinator webs, both of which contain birds and reptile pollinators in addition to
insects. Once constructed, we discuss the likely impact of invasive species on network
structure and the likely success of the restoration effort on native plant–pollinator
interactions.
20
MATERIALS AND METHODS
Study area and sites
Our study was conducted in the Black River Gorges National Park of
25 Mauritius (20°42′ S, 57°44′ E; 6754 ha; Fig. S1a). The area comprises the last
6 remnants of Erica/Phylica-heath plant community, a formerly widespread vegetation
type (Strahm, 1994). In Mauritius, it now occurs in only two small area of in total <
0.8 km2 at Plaine Champagne and Pétrin. The habitat is characterised by dwarf forest
and a high diversity of woody flowering plant species (Strahm, 1994).
5 Since 1986, the National Parks and Conservation Service and the non-
governmental Mauritian Wildlife Foundation have established ten Conservation
Management Areas (CMAs; total area 44 ha) across all major Mauritian habitat types
with the aim of restoring small areas of native flora. Each CMA is fenced, and
introduced plants are hand-weeded twice a year. For this study we selected two sites,
10 one restored and one unrestored (henceforth called restored and control sites
respectively) within an area of the same vegetation type. The restored site was Pétrin
CMA (6.2 ha), which was first weeded in 1994. Pétrin CMA represents the last
sample of an original heath community in Mauritius. The control site was of equal
size in an unmanaged area, 0.54 km from the restored site. Both sites are situated on
15 the Pétrin heathland plateau which is surrounded by pine plantation. We selected the
sites based on three criteria; (1) they represented a homogeneous heath community
with similar native species diversity and abundance; (2) they are part of a continuous
habitat type with the same abiotic conditions (e.g. altitude, aspect, climate, slope, soil
etc.); (3) a distance of 0.54 km between the sites was considered sufficient for their
20 pollinator communities to be mostly independent. The majority of pollinator species
were small flies, moths and beetles which tend to have relatively short foraging
distance. Thus, although, we do anticipate that large-distance foragers such as birds
and honey bees may occasionally cross the distance between the sites, we believe that
their effect is negligible in the community context. (see Fig. S1b). The major
25 difference between the plant communities of the restored and control site was the
7 dominance of invasive alien plants at the control site. In parts, strawberry guava
Psidium cattleianum Sabine (Myrtaceae) and other introduced woody plant species
form a continuous, almost monospecific stand with a maximum height of 1–1.5 m
depriving the heath community at the control site of the characteristic open structure
5 of the restored site.
At both study sites, we marked out a rectangular study area (330 × 100 m) in
which we set up 23 parallel 100 m transects, at intervals of 15 m (Fig. S1b). Transects
were divided into five 20 m sections. Sampling was conducted along these transects
using a stratified, random approach.
10
Plant communities
To determine plant species abundance, we surveyed the plant communities in
March 2003 by recording every individual of all woody flowering species in the study
areas. For P. cattleianum plants at the control site, we counted the number of
15 individuals > 30 cm in height in 10 random 1-m2 plots along each transect to obtain an
estimate of its abundance.
To produce a quantitative measure of flower density over time, we conducted
random flower counts in cubic meters along all 23 transects at each study site. Flower
counts were carried out every two weeks from September 2003 to March 2004 (see
20 Appendix I). Floral abundance, the mean number of flowers per cubic meter, was
calculated for each species by dividing the total number of flowers by the total
number of cubes sampled for each site (n = 3450).
Pollinator communities
8 Plant–animal interactions were recorded for all woody plant species which
flowered between 15th September 2003 and 15th March 2004. In each 2-week period,
we identified species, which were either flowering or were expected to start flowering
within the next week. Pollinator observations were conducted on each plant species
5 for four 30-min observation sessions, totalling 2 hours of observation per species per
2-weeks. We recorded the identity of all flower visitors which touched the sexual
parts of flowers, the number of flowers observed, and the number of visits by each
pollinator, and expressed pollinator activity as visitation rate, i.e. the number of visits/
flower/hour to account for differences in floral abundance and flowering duration.
10 Each visitor approaching a flowering plant was considered a new individual and was
thus recorded as a separate visit (see Appendix I for further details).
Pollination webs
Quantitative pollination webs were illustrated as bi-partite visitation graphs
15 (Jordano, 1987). In such webs, a line between two vertices represents an interaction
between the animal and the plant species. Here, floral abundance data were collected
following a stratified sampling scheme along transects, and data on flower visitation
were obtained with local observations. To scale the data gathered by the two sampling
techniques, we expressed the visitation rate to a plant species as a function of its floral
20 abundance in the study site. We define quantitative visitation rate of i on j as the total
number of visits/flower/hour of animal species i multiplied by the floral abundance of
the plant species j visited by i. That is, each visit was weighted by the floral
abundance of the interaction partner. We used the total number of visits of each
animal species as a measure of abundance of a visitor species. The overall pollination
25 webs of the entire season were drawn by programmes written in Mathematica™
9 (Wolfram Research, Inc., Champaign, IL, USA) and the webs for individual insect
orders were drawn by a programme written in Microsoft Visual Basics (Microsoft
Corporation 2004, Redmond, WA, USA).
5 Structure of pollination webs
Pollination webs are characterised by a number of parameters. We calculated
the following descriptive statistics for each web: number of plant species (P), number
of flower visitor species (A), species richness (R = P + A), web size (i.e. total number
of potential interactions, S = P × A), total number of interactions recorded (I), and the
10 total number of visits recorded (V). We also measured network connectance, C = 100
× (I/S) , which is the fraction of realised interactions in the network (Jordano, 1987).
During the season, network composition and size can fluctuate because plants and
animals can ‘join’ or ‘leave’ the network (Basilio, et al. 2006), thus C based on the
overall community could overestimate the level of generalisation. Therefore, we
15 calculated the overall connectance based on the mean connectance for each fortnightly
period (see Medan, et al., 2006). We also determined mean linkage for animal (la) and
plant species (lp), i.e. mean number of interactions per species, and the linkage of the
most-connected animal and plant species (lmax).
In addition to these qualitative descriptors, we computed quantitative
20 equivalents which account for the magnitude of an interaction (here quantitative
visitation rate) and were based on the Shannon measure of entropy H. Following
Bersier, et al., (2002), we calculated (1) unweighted plant (lup) and animal linkage
(lua), (2) weighted plant (lwp) and animal linkage (lwa), and (3) quantitative
connectance (Cq),which is weighted by the quantitative visitation rate of each taxon.
25 In addition, quantitative interaction evenness (ε) was calculated as: ε =
10 Σ(pi*log2(pi))/log2(N) where pi is the proportion of the total quantitative visitation
rate (N) represented by interaction i (see Tylianakis, et al., 2007). In contrast to
unweighted linkage, weighted linkage gives individual weight to each taxon
respective of its total interaction strength and, thus, better captures the functional
5 importance of taxa in the pollination web. Plant and animal linkage are equivalent to
the measures of generality and vulnerability in food webs. The descriptors were
calculated for the 13 two-week webs covering the entire main flowering season of
both sites.
10 Data analysis
On the community level, floral and plant abundance of native species may be
affected by the presence of invasive plants, which in turn can affect pollinator
diversity and behaviour. Thus, to describe the relationship of floral and plant
abundance between sites, to test whether visitation rate of a plant species is dependent
15 on its abundance, and to test whether plant species linkage is related to the total
number of visits received we used linear mixed effects models. The fixed effect ‘Site’
was entered first in the model to minimise potential site effects before calculating
other main effects, and to account for dependences within plant species, plant identity
was included in the model as a random effect. Floral and plant abundance and
20 quantitative visitation rate were ln-transformed to reach normality. All analyses were
conducted with the statistical package R 2.1.1 (R Development Core Team, 2005;
libraries used: MASS, nlme)
RESULTS
25 Plants
11 Overall, 105 flowering plant species were recorded in the plant survey, of
which 87 species (92.6 % of all individuals) flowered between August 2003 and
March 2004 (Appendix II). The remaining 18 species flowered during the winter
months from April to August, two of which (Philippia brachyphylla and Phylica
5 nitida) accounted for 78% of all winter-flowering individuals. The restored site
contained 74 flowering plant species and the control site 64 species, and 51 plant
species (95.6% of all individuals) occurred at both sites. Thirty-three of the flowering
species (37.9%) were either endangered or critically endangered following the IUCN
Red List criteria. Zero plant species at the restored site and eight plant species at the
10 control site were introduced. The introduced plant species accounted for 15.4% of the
total floral abundance in this community, but only 7.5% of all flower visits were
observed on these species. Of the eight introduced plant species at the control site
only five were visited by pollinators. All introduced species produced abundant fruits
despite their relatively low visitation rate.
15 Both sites were dominated by a few common plant species (Fig. 1, S2-S6;
Appendix II). At the restored site, the three most abundant flowering species
accounted for 30% of all plant individuals while introduced plants accounted for
82.8% of all plant individuals at the control site, but only for 9.5% of all species (Fig.
2). The abundance of plant species which occurred at both sites was significantly
20 higher in the restored compared to the unrestored site (paired t = 3.48, p = 0.001, df =
50). Floral abundance was dependent on the length of the flowering period of the
given plant species (F1,45 = 12.1, p < 0.0001) and on plant species abundance (F1,45 =
33.6, p < 0.0001), both traits which are likely to be affected by increased competition
for space and resources with invasive plants. Plant abundance of species which
25 occurred at both sites was positively related to visitation rate (F1,48 = 4.95, p = 0.031).
12 Similarly, there was a positive relationship between plant abundance and linkage
2 2 (restored: R = 0.14, F1,72 = 12.09, p = 0.001; control: R = 0.17, F1,62 = 12.90, p =
0.001).
The majority of flowering species produced open (23.0%), cup-shaped
5 (33.3%) or brush (18.4%) flowers, which were easily accessible to a wide range of
flower visitors. The dominating petal colours were white (36.8%), cream (27.6%). and
pale pink (19.5%). The main exceptions were Trochetia blackburniana Bojer
(Malvaceae; red flowers), Syzygium mauritianum Guého & Scott (Myrtaceae; red) and
Roussea simplex Sm. (Rousseaceae, yellow) with showy, conspicuous, and brightly
10 coloured flowers, which offered large amounts of nectar. These plant species were
also among the few that were visited by vertebrate pollinators.
Pollinators
Overall, there were 161 animal species visiting flowers (Appendix III; 79 spp.
15 were identified to species level accounting for 74.2% of all interactions, genus: 32
spp./ 23.5%, subfamily: 12 spp./3.7%, family: 36 spp./1.7%, order: 3 spp./0.1%; see
Figure S2-S6) from 65 families within five invertebrate and two vertebrate orders.
Seventy-four species occurred at both sites, of which 23 species were introduced. Of
all pollinator species, 45 were endemic or native to Mauritius (restored vs control =
20 40 vs 32 spp.), 35 were introduced (33 vs 26 spp.), and no origin could be determined
for 81. Of all visits, the latter group accounted for only 9%, native and endemic
species carried out 28%, and introduced animals accounted for 63%. Overall, 77
species were observed only once or twice, and only 14 species were recorded on
flowers > 100 times.
13 During 35 hours of nocturnal observations, we observed 19 (11.8%) pollinator
species visiting a total of 19 plant species across the entire season. At the restored site,
18 pollinator species visited 18 plant species, and at the control site 6 pollinator
species visited 7 plant species. Nocturnal interactions accounted for 4.6% and 2.1% of
5 interactions in the restored and the control site, respectively.
The most species-rich group of flower visitors were the true flies (Diptera; 71
species; see Figures S3) and, within this order, 26 species belonged to the families
Muscidae (house flies) and Syrphidae (hover flies). Social and solitary bees, which
represent a major group of flower visitors in most mainland pollinator communities
10 were extremely species-poor in our study with only one species in the family Apidae
(Apis mellifera L.) and one solitary species in the family Colletidae (Paleorhiza sp.)
(See Figure S2). The largest difference in number of visitor species between the sites
was seen in the Lepidoptera (30 spp. at the restored vs 17 spp. at the control site; See
Figure S4). Dipterans were the most abundant flower visitors (41.7% of all visits)
15 followed by hymenopterans (excluding Formicidae: 19.6%) and the Formicidae
(14.2%) (see Figure S6).
The honey bee (Apis mellifera) was overall the most abundant flower visitor in
the study, accounting for 15.8% of all visits. At the restored site, honey bees and the
widespread fly Stomorhina lunata Fabricius (Calliphoridae) were equally abundant
20 (together 27.6% of all visits), followed by the introduced yellow-footed ant
Technomyrmex albipes Smith (10.0%) and the native ant Brachymyrmex sp (8.4%;
both Formicidae). The ranking of flower visitor abundance was similar at the control
site except that, after A. mellifera (19.4% of visits), the accidentally introduced flea
beetle Chaetocnema sp. (Chrysomelidae; see also Figure S5) was the second most
25 abundant species (16.9%), followed by S. lunata (6.8%), Brachymyrmex sp. (5.2%),
14 and T. albipes (4.6%). Honey bees interacted with 43 plant species at the restored and
28 species at the control site (51% vs 44%). Of these, only three species at both sites
were visited by ≤ 3 pollinator species, including honey bees, suggesting that honey
bees did not serve as pollinators for many specialised plant species.
5 Flower visitors of both vertebrate groups contributed to 0.7% of all visits at the
restored site and 0.1% at the control site. Nevertheless, the single gecko species in the
study area, the Blue-tailed Day Gecko Phelsuma cepediana Merrem, visited 12 plant
species at the restored site and three species at the control site (16% vs 5%). Similarly,
birds visited more plant species (8 vs 2) at the restored than the control site. Overall,
10 there were three plant species where vertebrates, particularly P. cepediana, were the
sole regular flower visitors (Fig. 1; Appendix IV). Of the four observed vertebrate
flower visitors, the two generalist bird species, the Madagascar Fody Foudia
madagascariense and the Red-whiskered Bulbul Pycnonotus jocosus were both
introduced to Mauritius, and these were observed to forage for nectar on flowers at the
15 restored site only once. In contrast, the endemic Grey White-eye Zosterops
mauritianus and P. cepediana were regular flower visitors of 16 plant species at the
restored site, 11 of which were not visited by vertebrates at the control site. Ten of 11
plant species visited by P. cepediana were also visited by A. mellifera, suggesting
strong potential for resource competition between introduced and endemic pollinators.
20 The two species were observed to interact on the same plant only during nine out of
65 observation sessions. While P. cepediana made 11 visits to plants where A.
mellifera was present, it visited the same plants 33 times when A. mellifera was
absent. Apis mellifera also avoided plants where P. cepediana was present (82 vs
128). In one case, we have observed aggressive behaviour of A. mellifera towards P.
25 cepediana when feeding on the male flowers of Pandanus barklyi.
15 Structure of pollination webs
Pollination web descriptors on both plant–pollinator communities are
presented in Table 1. Mean quantitative evenness and connectance based on 13 two-
5 weekly sub-webs were not significantly different between sites (p > 0.1, paired t-test;
Table 2). Both web parameters showed no consistent patterns with regards to higher
or lower values in the restored compared to the control site across the two-weekly
sub-webs. Floral abundance was almost twice as high at the restored as at the control
site, and regarding quantitative visitation rate, the web of the restored site was 1.8
10 times larger.
Five percent of plant species at the restored site and 18.8% at the control site
received ≤ 3 visits. On average, at the control site there were 0.48 ± 0.19 (hereafter
means ± SE unless otherwise stated) visits/flower/hour to introduced plants compared
to 0.59 ± 0.11 to native plants. In comparison, mean visitation rate to native plant
15 species at the restored site was 0.70 ± 0.20 visits/flower/hour. Visitation rates to all
plant species at both sites are presented in Appendix II.
There were plant species at both sites which received no visitors during the
study (Fig. 3a). On average, linkage of plant and animal species which occurred at
both sites was higher at the restored than the control site (Table 3). Linkage of native
20 plant species did not differ to that of introduced species (native: 8.91 ± 1.2;
introduced: 4.6 ± 2.3; bootstrapped 95% CI 4.25 – 14.25). The majority of flower
visitors were observed to visit only one or two plant species (Fig. 3b). At the same
time, both pollinator communities contained few super-generalist species with a
linkage > 20.
16 Mean quantitative plant and animal linkage showed a similar pattern compared
to qualitative linkage. Both weighted and unweighted linkage of plants appear
approximately two-fold larger than the respective linkage value for animals. Neither
weighted nor unweighted linkage of plants and animals differed between sites (Table
5 2).
DISCUSSION
While a few extensive studies report qualitative information on plant-
pollinator communities (e.g. Inoue et al., 1990; Kato et al., 1990; Petanidou, 1991,
10 Kato, 2000), our study presents two of the most extensive, highly resolved and
comprehensive fully-quantitative plant–pollinator webs to date which can be analysed
with a food web approach. The pollination webs include all woody plant species
which flowered between August 2003 and April 2004 independent of flowering time
(diurnal or nocturnal), length of flowering period and range of pollinator species. The
15 methodological setup of repeated two-weekly sampling resulted in a high temporal
and spatial resolution of the webs, minimising the chance of sampling bias.
By focusing on the community level there is loss of accuracy with respect to
pollination efficiency of individual visitors. Not all flower-visitors are pollinators, and
the pollination efficiency of those that are varies with plant species (Schemske and
20 Horvitz, 1984). Vázquez et al. (2005, and references within), however, advocated that
visitation frequency of flower visitors is an appropriate surrogate for per-capita
pollination efficiency, and pollinator efficiency plays a smaller role (see also Sahli
and Conner, 2006).
Due to the scarcity of heath habitats in Mauritius and the intensity of the data
25 collection, the study could not be replicated over several restored and control sites. As
17 far as possible we statistically accounted for spatial and temporal dependencies of
errors between sites and plant and animal species by using linear mixed-effect models
and paired t-tests. Thus, the findings presented in this study suggest that the structural
differences in the plant and pollinator communities are tied to habitat restoration in
5 the Conservation Management Area.
Plants
Theoretical and empirical studies have shown that plant population density is
positively correlated with plant fitness (e.g. Silander and Primack, 1978; Klinkhamer,
10 et al., 1989). We showed that plant abundance of most native species was higher at
the restored than the control site, and that it was positively related to the number of
pollinator species and visitation rate. Consequently, the relatively lower frequency of
rare or locally rare plant species at the control site could have detrimental effects on
the quality and quantity of pollen dispersal of those native plants in the degraded area
15 (Oostermeijer, et al., 2000). It has been shown that spatial isolation on the level of
neighbouring plant species has resulted in reproductive decline for a variety of plants
(Ghazoul, 2005; Knight, et al., 2005; but see Feinsinger, et al., 1986). Many
pollinators respond to the relative abundance of plants and/or flowers in a density-
dependent manner when foraging for floral resources (Smithson and Macnair, 1997;
20 Fleishman et al., 2005). As most plant species in Pétrin produce inconspicuous, small
flowers, invasion of introduced plant species, even if the actual abundance of native
plants and their flowers remains unaffected in the short-term, is likely to have a
considerable effect on the foraging behaviour of pollinators, and eventually on the
reproduction of self-incompatible native plants.
18 The eight introduced plant species at the control site accounted for almost 83%
of all plant individuals in the area. Nonetheless, direct competition between
introduced and native plants for flower visitations appears low. The combination of
abundant invasive plant species and low attraction to pollinators appears to contrast an
5 invasion scenario proposed by Aizen et al. (2008). The authors suggest that plant
invasion and increase in attractiveness to pollinator is complimentary. In our study,
introduced plant species showed low linkage: three species (Ossaea marginata,
Clidemia hirta, Ardisia crenate) received no visitors and only one visit was observed
to a fourth, Wikstroemia indica. This implies that these introduced species rely little
10 on the local pollinator community for reproduction, which is a common strategy to
overcome pollen limitation by invasive alien plant species (Baker's rule; Baker, 1967).
Similarly, Memmott and Waser (2002) and Olesen, et al. (2002) described fewer
flower visitors on introduced compared to native species in a plant community in
central USA (but see Morales and Aizen 2002, 2006). However, we may have
15 recorded a transient pattern in Mauritius because invaders with attractive floral
resources were less abundant at the control site than at other locations on the island,
where they received many more visits by a range of pollinators (C. Kaiser-Bunbury,
pers. obs.). Thus, invasion may have been still in the early stages, despite clear signs
in the pollination web structure (see section below the “Structure of pollination
20 webs”).
Pollinators
In our study, dipterans were the most abundant flower visitors, a pattern
commonly observed in pollination assemblages in high latitudes (e.g. Elberling and
25 Olesen, 1999), high altitudes (e.g. Arroyo, et al., 1982; Inouye and Pyke, 1988) and
19 on islands (e.g. Anderson, et al., 2001). Flies have been widely acknowledged as
potential pollinators of many plant species (Kearns, 2001) and generalist species
overcome their low efficiency as pollinators with their abundance, particularly when
more efficient pollinators are absent (McGuire and Armbruster, 1991). Native and
5 endemic pollinators accounted for only 28% of visits whereas introduced animals
accounted for 63% (unknown origin 9%), which illustrates the dominance of
introduced pollinators in the communities. While these numbers do not necessarily
reflect the contribution of native or introduced flower visitors to pollination, they
provide a possible explanation for the demise of native pollinator diversity in Pétrin.
10 All vertebrates were more abundant and more highly connected at the restored
site compared to the control site. The role of lizards in pollination has been considered
vital to the reproduction of many native Mauritian plant species (Nyhagen, et al.,
2001; Hansen, et al., 2007), and on other islands, for example the Balearic Islands
(Olesen and Valido, 2003, and references therein). The endemic blue-tailed day gecko
15 Phelsuma cepediana is an important pollinator of several endangered plant species in
Pétrin, e.g. Trochetia blackburniana (Hansen, et al., 2006) and Roussea simplex
(Hansen, 2005). Male Phelsuma geckos are territorial and their abundance is related
to habitat composition and quality (Harmon, 2005). The low structural diversity and
the lack of suitable habitat for geckos at the control site probably contributed to the
20 low density of P. cepediana in the degraded habitat. Similarly, the foraging behaviour
of the endemic grey white-eye Zosterops mauritianus, which was more frequently
encountered at the restored site, appears to be linked to habitat composition and the
availability of floral resources (Hansen, et al., 2002; Kaiser, et al., 2008). A similar
relationship between pollinator occurrence and habitat composition was described
25 from conservation areas in the Cape Floral Region (Pauwn, 2007). There, soil type
20 and succession stage of the vegetation, both anthropogenically altered, reduced seed
set of six native plant species that rely on the pollination by the oil-collecting bee
Rediviva peringueyi, indicating a strong relationship between habitat structure and
pollinator services.
5 The most abundant and highly linked flower visitor was the introduced honey
bee Apis mellifera. Given that no artificial beehives were maintained within or close
to the boundaries of the National Park for the duration of the study (National Parks
and Conservation Service Mauritius, pers. comm.) it is likely that the majority of
honey bees belonged to natural or naturalised populations. One reason for the high
10 visitation frequency of honey bees may be their prolonged flight and foraging season,
which result in an overlap in foraging time with most co-occurring pollinator species.
Therefore, honey bees may be strong competitors for floral resources (e.g. Eickwort
and Ginsberg, 1980; Dupont, et al., 2004). At the same time, honey bees may be
beneficial, by ensuring pollination for many plants. Due to their abundance and
15 generalist foraging pattern, they can serve as pollinators to rare plant species, where
the original pollinators may be extinct. In contrast to findings from Mediterranean
plant–pollinator communities where honey bees are strongly associated with
specialised plant species (i.e. plants with low linkage; Petanidou and Potts, 2006),
honey bees in Pétrin were equally associated with common, generalised plant species
20 and poorly visited, rare species, a pattern frequently observed in highly generalised
taxa in pollination webs (interaction asymmetry; e.g., Bascompte, et al., 2003;
Vázquez and Aizen 2004; Kaiser 2006). We did not observe a disproportionate
increase in honey bee linkage or abundance at the invaded site in contrast to findings
by Aizen et al. (2008). Nevertheless, the honey bee and other introduced pollinator
25 species such as the flies Stomorhina lunata and Pachycerina crinicornis and the bettle
21 Chaetocnema sp 1 can certainly be regarded as super-generalist with the potential to
modify network structure (e.g. invasive generalist plant species affect nestedness;
Bartomeus et al. 2008), but the role of habitat restoration in these processes remains
unclear.
5
Structure of pollination webs
There were almost twice as many flowers at the restored than the control site,
and the web of the restored site was 1.8 times larger with regards to quantitative
visitation rate, indicating an overall higher complexity at the restored site. With an
10 increase in the total amount of resources available in the community we observed a
relative increase in attractiveness of all plants to pollinators, an observation previously
described by Fleishman et al., (2005) (see also Morales and Aizen, 2006). Also,
mutualistic interaction strength declines at heavily invaded sites, which could be one
explanation why the control site has substantially lower quantitative visitation rates
15 than the restored site shown by the overall smaller web (Aizen et al. 2008). Both webs
were characterised by a few abundant species, highly linked hubs, and by many rare
species with weak interactions, indicated by higher weighted compared to unweighted
linkages, similar evenness, and quantitative connectance at both sites. Qualitative
connectance was twice as high as in highly diverse Mediterranean pollination web and
20 two-thirds of the mean connectance in a temperate forest in Argentina, the only two
published networks for which connectance was corrected for the extended sampling
period (Basilio, et al. 2006; Medan, et al., 2006). However, since connectance is size-
dependent, its use as an index of generalisation in tropical and temperate pollination
systems is questionable (Kay and Schemske, 2004; but see Petanidou and Potts,
25 2006). Here, the quantitative linkage is independent of network size and should be
22 preferred because it depicts biologically meaningful community-specific differences
and reduces the risk of misinterpretation due to sampling bias (see Goldwasser and
Roughgarden, 1997). For example, both plant and animal mean weighted linkage is
higher than the unweighted linkage (Table 2) indicating that plants and animals in the
5 webs tend to form generalist hubs, i.e. generalist pollinator species interact relatively
strongly with generalist plant species and vice versa. This pattern appeared to be even
slighlty stronger for plant species in the restored site compared to the control site (lwp
5.12 vs. 4.44).
To our knowledge, however, there are no pollination web studies to date that
10 present quantitative parameters allowing comparisons of general patterns across
different ecosystems. Thus, comparisons can so far only be based on qualitative
parameters. Animal species at both sites showed a similar degree of generalisation and
plant species at the restored site interacted, on average, with almost two species more
than plant species at the control site (see Table 1 and Appendix II). While mean plant
15 linkage in our study lies well within the range of linkage values from the 29 plant–
pollinator communities presented by Jordano et al. (2006), the mean pollinator linkage
is high in comparison to the webs reported by the authors—only one artic pollinator
community shows a higher degree of generalisation (see also Morales and Aizen,
2006). Thus, both pollinator communities reflect common feature of many island
20 plant–pollinator communities (Barrett, 1996; Anderson, et al., 2001), and even plant
linkage in our webs is comparatively high when we consider that island plants tend to
be less generalised than mainland species (Olesen and Jordano, 2002). One
contributing factor to the high degree of generalisation could be the comparatively
low ratio of animal to plant species (see Table 1; A/P ratio is amongst the lowest of
25 the networks presented by Jordano, et al., 2006) resulting from a depauperate
23 pollinator fauna in comparison to mainland communities (MacArthur and Wilson,
1967).
Plant species which interact with numerous pollinator species, and vice versa,
may be important for the structure and stability of plant–pollinator communities. For
5 example, generalised species have a high resource overlap, which may result in strong
direct and indirect competition for floral resources (between pollinator species) or for
pollination services (between plant species). In our study, the most dominant and
generalised pollinators were introduced invertebrates. Those species showed
substantial niche overlaps with native pollinators such as birds, geckos, butterflies,
10 and flies, and consequently native pollinators may be displaced to less profitable
sources of food (e.g. the honey bee; Hansen, et al., 2002). An advantage of
generalised systems is resilience against disturbances. The stability of plant–pollinator
communities is thought to increase with a high degree of redundancy in pollinators
because adverse events are unlikely to affect all species equally severely (Lawton,
15 1994; Memmott, et al., 2004). At the control site, 43.8% of plant species received
fewer than four visitors compared to 14.9% at the restored site, thus, if a high level of
generalisation can ‘secure’ against the collapse of plant–pollinator webs, the control
site may be more vulnerable to perturbations.
20 Implications for conservation
Both sites were relatively similar in terms of native plant species richness, but
habitat composition at the control site was heavily altered by the presence of invasive
species. The degradation of heath habitat in some areas of Pétrin by introduced plants
had a strong effect on plant abundance and the diversity of plant and pollinator
25 assemblages and interactions in these areas. The similar dominance of introduced
24 generalist flower visitors at both sites indicated that, for common animal species,
structural difference between plant communities had little effect on their foraging
behaviour. Native pollinator species richness and density, however, were higher at the
restored site, which is may to be a consequence of habitat restoration. For example,
5 bird and gecko visitation was almost absent at the control site, and both groups of
pollinators have been shown to be sensitive to changes in plant community
composition (Hansen, et al., 2007; Kaiser, et al., 2008). The relationship between
habitat composition and pollinator assemblages described in this study has
implications for the conservation of degraded habitats in Mauritius, on other oceanic
10 islands, and also in mainland ecosystems.
The diversity of a plant community may be related to the functional diversity
of its pollinator community (Fontaine, et al., 2006), and species-rich floras support a
higher diversity of pollinators (Kevan 1999). Differences in floral abundance affect
foraging decisions of insects (Waser and Real, 1979; Feinsinger, 1987), and insects
15 concentrate their foraging on dense patches of flowers (Thomson, 1981), which are
more common in habitats where native plants do not compete with invasives for
resources. To maintain pollinator diversity, one has to preserve structural diversity to
provide food sources, nesting and oviposition sites, and resting or mating sites
(Kevan, 1999).
20
Conclusion
Pollination web studies are useful tools to analyse plant–pollinator
assemblages of different habitat types. In our study we collected data for pollination
webs of two sites only and, thus, cannot deduce with certainty that the observed
25 differences between sites are due to habitat restoration. However, we can state that
25 both sites were similar in plant species richness but fairly distinct in plant and
pollinator community composition, which suggests that habitat restoration may
positively affect the functional ecosystem integrity of restored sites. Higher pollinator
species richness and abundance at the restored site indicated a positive effect of
5 habitat restoration on pollinator diversity, which may increase community stability
and secure a higher rate of pollination success of native plant species. For habitat
restoration to be successful in the long-term, practitioners should thus maintain
structural diversity to support a species-rich and abundant pollinator assemblage
which ensures native plant reproduction, despite frequent biotic and abiotic
10 perturbations.
ACKNOWLEDGEMENTS
We are very grateful to the National Parks and Conservation Service and the
Mauritian Wildlife Foundation who both supported us throughout the study. We
15 express particular gratitude to the NPCS team at Pétrin who helped with species
identification and during the field work. We also thank M. Allet, G. D’Argent, K.
Henson, K. Edmunds, G. D. Ramluguri, A. Ramsing, R. Atkinson, N. Bunbury, and
D. Hansen for help in the field. Animal species were kindly identified by J. Deeming,
B. Levey, D. Slade, K. Adlbauer, N. Springate, D. Quicke, W. Speidel, S. Couteyen,
20 J. Williams and S. Ganeshan. Valuable comments on the manuscript were provided by
N. Waser, J. Ollerton, J. Olesen, R. Atkinson, C. Kueffer and N. Bunbury. The project
was funded by the Swiss National Science Foundation (grant no. 631-065950 to
CBM) and by the Roche Research Foundation.
25 LITERATURE CITED
26 Aizen, M.A., Morales, C.L., Morales, J.M., 2008. Invasive mutualists erode native
pollination webs. Plos Biology 6, 396-403.
Anderson, G.J., Bernardello, G., Stuessy, T.F., Crawford, D.J., 2001. Breeding system
and pollination of selected plants endemic to Juan Fernandez Islands. Am. J. Bot.
5 88, 220-233.
Arroyo, M.T.K., Primack, R., Armesto, J., 1982. Community studies in pollination
ecology in the high temperate Andes of central Chile. I. Pollination mechanisms
and altitudinal variation. Am. J. Bot. 69, 82-97.
Baker, H.G., 1967. Support for Baker's law - as a rule. Evolution 21, 853-856.
10 Barrett, S.C.H., 1996. The reproductive biology and genetics of island plants. Philos.
Trans. R. Soc. Lond. Ser. B-Biol. Sci. 351, 725-733.
Bartomeus, I., Vilà, M., Santamaría, L., 2008. Contrasting effects of invasive plants in
plant–pollinator networks. Oecologia 155, 761-770.
Bascompte, J., Jordano, P., Olesen, J.M., 2006. Asymmetric coevolutionary networks
15 facilitate biodiversity maintenance. Science 312, 431-433.
Basilio, A.M., Medan, D., Torretta, J.P., Bartoloni, N.J., 2006. A year-long plant-
pollinator network. Austral Ecol. 31, 975-983.
Bersier, L.F., Banasek-Richter, C., Cattin, M.F., 2002. Quantitative descriptors of
food-web matrices. Ecology 83, 2394-2407.
20 Blüthgen, N., Menzel, F., Hovestadt, T., Fiala, B., Blüthgen, N., 2007. Specialization,
constraints, and conflicting interests in mutualistic networks. Current Biology 17,
341-346.
Cheke, A.S., 1987. An ecological history of the Mascarene Islands, with particular
reference to extinctions and introductions of the land vertebrates. In: Diamond,
27 A.W., (Ed.) Studies of Mascarene Island birds. Cambridge University Press;
Cambridge, pp. 1-89.
Crawley, M.J., 2007. The R book. John Wiley & Sons, Chichester, UK.
Dicks, L.V., Corbet, S.A., Pywell, R.F., 2002. Compartmentalization in plant-insect
5 flower visitor webs. J. Anim. Ecol. 71, 32-43.
Dupont, Y.L., Hansen, D.M., Valido, A., Olesen, J.M., 2004. Impact of introduced
honey bees on native pollination interactions of the endemic Echium wildpretii
(Boraginaceae) on Tenerife, Canary Islands. Biol. Conserv. 118, 301-311.
Eickwort, G.C., Ginsberg, H.S., 1980. Foraging and mating-behavior in Apoidea.
10 Annual Review of Entomology 25, 421-446.
Elberling, H., Olesen, J.M., 1999. The structure of a high latitude plant-flower visitor
system: the dominance of flies. Ecography 22, 314-323.
Feinsinger, P., Murray, K.G., Kinsman, S., Busby, W.H., 1986. Floral neighborhood
and pollination success in four hummingbird-pollinated cloud forest plant species.
15 Ecology 67, 449-464.
Feinsinger, P., 1987. Effects of plant species on each others pollination - is
community structure influenced? Trends in Ecology & Evolution 2, 123-126.
Fleishman, E., Mac Nally, R., Murphy, D.D., 2005. Relationships among non-native
plants, diversity of plants and butterflies, and adequacy of spatial sampling.
20 Biological Journal of the Linnean Society 85, 157-166.
Fontaine, C., Dajoz, I., Meriguet, J., Loreau, M., 2006. Functional diversity of plant-
pollinator interaction webs enhances the persistence of plant communities. Plos
Biology 4, 129-135.
Ghazoul, J., 2004. Alien abduction: disruption of native plant-pollinator interactions
25 by invasive species. Biotropica 36, 156-164.
28 Ghazoul, J., 2005. Pollen and seed dispersal among dispersed plants. Biological
Reviews 80, 413-443.
Goldwasser, L., Roughgarden, J., 1997. Sampling effects and the estimation of food-
web properties. Ecology 78, 41-54.
5 Hansen, D.M., 2005. Pollination of the enigmatic Mauritian endemic Roussea simplex
(Rousseaceae): birds or geckos? Ecotropica 11, 69-72.
Hansen, D.M., Beer, K., Müller, C.B., 2006. Mauritian coloured nectar no longer a
mystery: a visual signal for lizard pollinators. Biology Letters 2, 165-168.
Hansen, D.M., Kiesbüy, H.C., Jones, C.G., Müller, C.B., 2007. Positive indirect
10 interactions between neighboring plant species via a lizard pollinator. Am. Nat.
169, 534-542.
Hansen, D.M., Olesen, J.M., Jones, C.G., 2002. Trees, birds and bees in Mauritius:
exploitative competition between introduced honey bees and endemic
nectarivorous birds? J. Biogeogr. 29, 721-734.
15 Harmon, L.J., 2005. Competition and community structure in day geckos (Phelsuma)
in the Indian Ocean. PhD. Washington University, Saint Louis, Missouri.
Hobbs, R.J., Norton, D.A., 1996. Towards a conceptual framework for restoration
ecology. Restor. Ecol. 4, 93-110.
Inoue, T., Kato, M., Kakutani, T., Suka, T., Itino, T., 1990. Insect–flower relationship
20 in the temperate deciduous forest of Kibune, Kyoto: an overview of the flowering
phenology and the seasonal pattern of insect visits. Contribution from Biological
Laboratory, Kyoto University 27, 377-463.
Inouye, D.W., Pyke, G.H., 1988. Pollination biology in the Snowy Mountains of
Australia: comparisons with montane Colorado, USA. Aust. J. Ecol. 13, 191-210.
29 Johnson, S.D., Steiner, K.E., 2000. Generalization versus specialization in plant
pollination systems. Trends in Ecology & Evolution 15, 140-143.
Johnson, S.D., Steiner, K.E., 2003. Specialized pollination systems in southern Africa.
South African Journal of Science 99, 345-348.
5 Jordano, P., 1987. Patterns of mutualistic interactions on pollination and seed
dispersal: connectance, dependence, asymmetries and coevolution. The American
Naturalist 129, 657-677.
Jordano, P., Bascompte, J., Olesen, J.M., 2006. The ecological consequences of
complex topology and nested structure in pollination webs. In: Waser, N.M.,
10 Ollerton, J., (Eds.) Plant-pollinator interactions: from specialization to
generalization The University of Chicago Press; Chicago, pp. 173-199.
Kaiser, C.N., 2006. Functional integrity of plant-pollinator communities in restored
habitats in Mauritius. University of Zürich, Zürich.
Kaiser, C.N., Hansen, D.M., Müller, C.B., 2008. Habitat structure affects reproductive
15 success of the rare endemic tree Syzygium mamillatum (Myrtaceae) in restored and
unrestored sites in Mauritius. Biotropica 40, 86-94.
Kanstrup, J., Olesen, J.M., 2000. Plant-flower visitor interactions in a neotropical rain
forest canopy: community structure and generalisation level. In: Totland, O., (Ed.)
The Scandinavian Association for Pollination Ecology honours Knut Faegri. Det
20 Norske Videnskaps-Akademi; Oslo, pp. 33-41.
Kato, M., 1996. Plant-pollinator interactions in the understory of a lowland mixed
dipterocarp forest in Sarawak. Am. J. Bot. 83, 732-743.
Kato, M., 2000. Anthophilous insect community and plant-pollinator interactions on
Amami Islands in the Ryukyu Archipelago, Japan. Contribution from Biological
25 Laboratory, Kyoto University 29, 157-252.
30 Kato, M., Kakutani, T., Inoue, T., Itino, T., 1990. Insect-flower relationship in the
primary beech forest of Ashu, Kyoto: an overview of the flowering phenology and
the seasonal pattern of insect visits. Contribution from Biological Laboratory,
Kyoto University 27, 309-375.
5 Kato, M., Kawakita, A., 2004. Plant-pollinator interactions in New Caledonia
influenced by introduced honey bees. Am. J. Bot. 91, 1814-1827.
Kay, K.M., Schemske, D.W., 2004. Geographic patterns in plant-pollinator
mutualistic networks: Comment. Ecology 85, 875-878.
Kearns, C.A., 2001. North American, dipteran pollinators: assessing their value and
10 conservation status. Conserv. Ecol. 5, art. no.-5.
Kearns, C.A., Inouye, D.W., Waser, N.M., 1998. Endangered mutualisms: the
conservation of plant-pollinator interactions. Annu. Rev. Ecol. Syst. 29, 83-112.
Kevan, P.G., 1999. Pollinators as bioindicators of the state of the environment:
species, activity and diversity. Agriculture Ecosystems & Environment 74, 373-
15 393.
Klinkhamer, P.G.L., de Jong, T.J., de Bruyn, G.J., 1989. Plant size and pollinator
visitation in Cynoglossum officinale. Oikos 54, 201-204.
Knight, T.M., Steets, J.A., Vamosi, J.C., Mazer, S.J., Burd, M., Campbell, D.R.,
Dudash, M.R., Johnston, M.O., Mitchell, R.J., Ashman, T.-L., 2005. Pollen
20 limitation of plant reproduction: pattern and process. Annu. Rev. Ecol. Evol. Syst.
36, 467-497.
Lawton, J.H., 1994. What do species do in ecosystems. Oikos 71, 367-374.
Lopezaraiza-Mikel, M.E., Hayes, R.B., Whalley, M.R., Memmott, J., 2007. The
impact of an alien plant on a native plant pollinator network: An experimental
25 approach. Ecology Letters 10, 539-550.
31 MacArthur, R.H., Wilson, E.O., 1967. The theory of island biogeography. Princeton
University Press, Princeton.
Martinez, N.D., 1992. Constant connectance in community food webs. Am. Nat. 139,
1208-1218.
5 McGuire, A.D., Armbruster, W.S., 1991. An experimental test for reproductive
interactions between 2 sequentially blooming Saxifraga species (Saxifragaceae).
Am. J. Bot. 78, 214-219.
Medan, D., Basilio, A.M., Devoto, M., Bartoloni, N.J., Torretta, J.P., Petanidou, T.,
2006. Measuring generalization and connectance in temperate, year-long active
10 systems. In: Waser, N.M., Ollerton, J., (Eds.) Plant-pollinator interactions: from
specialization to generalization The University of Chicago Press; Chicago, pp.
245-259.
Memmott, J., 1999. The structure of a plant-pollinator food web. Ecology Letters 2,
276-280.
15 Memmott, J., Waser, N.M., 2002. Integration of alien plants into a native flower-
pollinator visitation web. Proceedings of the Royal Society of London B 269,
2395-2399.
Memmott, J., Waser, N.M., Price, M.V., 2004. Tolerance of pollination networks to
species extinctions. Proceedings of the Royal Society of London B 271, 2605-
20 2611.
Moldenke, A.R., 1975. Niche specialization and species-diversity along a Californian
transect. Oecologia 21, 219-242.
Momose, K., Yumoto, T., Nagamitsu, T., Kato, M., Nagamasu, H., Sakai, S.,
Harrison, R.D., Itioka, T., Hamid, A.A., Inoue, T., 1998. Pollination biology in a
32 lowland dipterocarp forest in Sarawak, Malaysia. I. Characteristics of the plant-
pollinator community in a lowland dipterocarp forest. Am. J. Bot. 85, 1477-1501.
Montalvo, A.M., Rice, S.L.W., Buchmann, S.L., Cory, C., Handel, S.N., Nabhan,
G.P., Primack, R., Robichaux, R.H., 1997. Restoration biology: a population
5 biology perspective. Restor. Ecol. 5, 277-290.
Morales, C.L., Aizen, M.A., 2002. Does invasion of exotic plants promote invasion of
exotic flower visitors? A case study from the temperate forests of the southern
Andes. Biol. Invas. 4, 87-100.
Morales, C.L., Aizen, M.A., 2006. Invasive mutualisms and the structure of plant-
10 pollinator interactions in the temperate forests of north-west Patagonia, Argentina.
J. Ecol. 94, 171-180.
Nyhagen, D.F., Kragelund, C., Olesen, J.M., Jones, C.G., 2001. Insular interactions
between lizards and flowers: flower visitation by an endemic Mauritian gecko. J.
Trop. Ecol. 17, 755-761.
15 Olesen, J.M., Eskildsen, L.I., Venkatasamy, S., 2002. Invasion of pollination
networks on oceanic islands: importance of invader complexes and endemic super
generalists. Diversity & Distributions 8, 181-192.
Olesen, J.M., Jordano, P., 2002. Geographic patterns in plant-pollinator mutualistic
networks. Ecology 83, 2416-2424.
20 Olesen, J.M., Valido, A., 2003. Lizards as pollinators and seed dispersers: an island
phenomenon. Trend Ecol. Evol. 18, 177-181.
Oostermeijer, J.G.B., Luijten, S.H., Petanidou, T., Kos, M., Ellis-Adam, A.C., Den
Nijs, H.C.M., 2000. Pollination in rare plants: is population size important? In:
Totland, O., (Ed.) The Scandinavian Association for Pollination Ecology honours
25 Knut Faegri. Det Norske Videnskaps-Akademi; Oslo, pp. 201-213.
33 Paine, R.T., 1980. Food webs - linkage, interaction strength and community
infrastructure. J. Anim. Ecol. 49, 667-685.
Percival, M., 1974. Floral ecology of coastal scrub in southeast Jamaica. Biotropica 6,
104-129.
5 Petanidou, T., 1991. Pollination ecology in a phryganic ecosystem. PhD dissertation.
Aristotelian University, Thessaloniki, Greece.
Petanidou, T., Potts, S.G., 2006. Mutual use of resources in Mediterranean plant-
pollinator communities: How specialized are pollination webs? In: Waser, N.M.,
Ollerton, J., (Eds.) Plant-pollinator interactions: from specialization to
10 generalization The University of Chicago Press; Chicago, pp. 220-244.
R Development Core Team, 2005. R: a language and environment for statistical
computing. in. R Foundation for Statistical Computing, Vienna.
Sahli, H., Conner, J., 2006. Characterizing ecological generalization in plant-
pollination systems. Oecologia 148, 365-372.
15 Schemske, D.W., Horvitz, C.C., 1984. Variation among floral visitors in pollination
ability - a precondition for mutualism specialization. Science 225, 519-521.
Silander, J.A., Primack, R.B., 1978. Pollination intensity and seed set in evening
primrose (Oenothera fruticosa). American Midland Naturalist 100, 213-216.
Simberloff, D., 1986. Introduced insects: a biogeographic and systematic perspective.
20 In: Mooney, H.A., Drake, D.R., (Eds.) Ecology of biological invasions of North
America and Hawaii. Springer Verlag; New York, pp. 3-26.
Simberloff, D., 1995. Why do introduced species appear to devastate islands more
than mainland areas? Pacific Science 49, 87-97.
34 Smithson, A.N.N., Macnair, M.R., 1997. Density-dependent and frequency-dependent
selection by bumblebees Bombus terrestris (L.) (Hymenoptera: Apidae).
Biological Journal of the Linnean Society 60, 401-417.
Strahm, W., 1994. The conservation and restoration of the flora of Mauritius and
5 Rodrigues. PhD thesis. University of Reading, Reading, UK.
Thomson, J.D., 1981. Spatial and temporal components of resource assessment by
flower-feeding insects. J. Anim. Ecol. 50, 49-59.
Traveset, A., Richardson, D.M., 2006. Biological invasions as disruptors of plant
reproductive mutualisms. Trends in Ecology & Evolution 21, 208-216.
10 Tylianakis, J.M., Tscharntke, T., Lewis, O.T., 2007. Habitat modification alters the
structure of tropical host-parasitoid food webs. Nature 445, 202-205.
Vázquez, D.P., Aizen, M.A., 2004. Asymmetric specialization: a pervasive feature of
plant-pollinator interactions. Ecology 85, 1251-1257.
Vázquez, D.P., Morris, W.F., Jordano, P., 2005. Interaction frequency as a surrogate
15 for the total effect of animal mutualists on plants. Ecology Letters 8, 1088-1094.
Waser, N.M., Chittka, L., Price, M.V., Williams, N.M., Ollerton, J., 1996.
Generalization in pollination systems, and why it matters. Ecology 77, 1043-1060.
Waser, N.M., Real, L.A., 1979. Effective mutualism between sequentially flowering
plant species. Nature 281, 670-672.
20 Whittaker, R.J., 1998. Island biogeography: ecology, evolution, and conservation.
Oxford University Press, Oxford.
25
35 Table 1 Pollination web parameters of both study site. We present the total number
of plant (P) and animals species (A), visits (V), and interactions (I), as well as the ratio
of animal per plant species, web size (S), connectance (C), maximal plant and animal
linkage (lmax), and mean ± SE plant (lp) and animal linkage (la).
5
Statistics restored control
Number of plant species (P) 74 64
Number of animal species (A) 135 100
Number of visits (V) 3961 3334
Number of interactions (I) 744 534
Ratio A/P 1.84 1.56
Network size (S) 9990 6400
Connectance (C) 13.23 15.57
Maximal plant linkage (lmax) 39 38
Maximal animal linkage (lmax) 45 34
Plant linkage (lp) 10.2 ± 1.06 8.34 ± 1.15
Animal linkage (la) 5.52 ± 0.71 5.39 ± 0.71
36 Table 2 Mean ± SE quantitative pollination web parameters of both study sites.
Means were calculated from 13 two-weekly webs in both the restored and the control
site. We present interaction evenness (ε), connectance (Cq), unweighted plant (luqp)
5 and animal linkage (lua), and weighted plant (lwp) and animal linkage (lwa). Means of
all parameters were not significantly different (p > 0.1, paired t-test) between sites,
but weighted linkage (log-transformed) was significantly higher (p < 0.001, paired t-
test) than unweighted linkage (log-transformed) for animal and plants at both sites.
Quantitative Statistics restored control
Evenness (ε) 0.70 ± 0.027 0.70 ± 0.026
Connectance (Cq) 0.075 ± 0.007 0.082 ± 0.006
Unweighted plant linkage (lup) 3.32 ± 0.38 3.08 ± 0.39
Unweighted animal linkage (lua) 1.57 ± 0.08 1.60 ± 0.06
Weighted plant linkage (lwp) 5.12 ± 0.47 4.44 ± 0.41
Weighted animal linkage (lwp) 2.32 ± 0.22 2.20 ± 0.20
10
37 Table 3 Linkage of plant and pollinator species which occurred at both sites.
Restored Control Plants Mean linkage ± SE 11.57 ± 1.41 9.15 ± 1.36 Median 9 5 paired t 2.93 df 50 p 0.005 Pollinators Mean linkage ± SE 9.06 ± 1.16 6.94 ± 0.92 Median 5.5 3 paired t 3.40 df 71 p 0.001
38 Figure 1 Quantitative pollination webs of plant–pollinator communities at (a) the
restored and (b) the control site. Visitor species are shown as rectangles at the top and
plant species are shown at the bottom (red rectangles depict introduced plant species).
The width of the rectangles reflects the relative abundance of flower visitors and
5 plants. Links represent interactions between species, and the width of the lines
indicates the relative quantitative visitation rate between an interacting pair of species.
Webs are drawn to the same scale. Full names to plant species abbreviations are
presented in Appendix II. Animal species codes are only given for a selection of
abundant pollinators referred to in the text. For all pollinator species codes see
10 Appendix III. Red: Hymenoptera, pink: Gekkonidae, light blue: Diptera, dark green:
Aves, light green: Hemiptera orange: Formicidae, dark blue: Coleoptera, and yellow:
Lepidoptera. 13. Apis mellifera, 17. Brachymyrmex sp, 26. Chaetocnema sp, 48.
Dysauxes florida, 56. Fannia pusio, 89. Melanostoma annulipes, 96. Musca
domestica, 98. Nacoleia sp 1, 107. Pachycerina crinicornis, 110. Panara naso, 113.
15 Pelecophora intemipta, 117. Phelsuma cepediana, 142. Stomorhina lunata, 150.
Technomyrmex albipes, 160. Zosterops mauritianus.
Figure 2 Endemic, native and introduced plant species (a) richness and (b)
abundance in both site.
20
Figure 3 Frequency of (a) plant linkage and (b) pollinator linkage in the restored and
the control site. Each bar represents the count of species with a given linkage (number
of taxa interacted with). The majority of pollinator species visited only one plant
species, and few pollinators were extremely generalised. Pollinator species with a low
25 linkage are less likely to be observed than species with a higher linkage. Species
39 identity is given for highly generalised plant species: 1. Sideroxylon cinereum, 2.
Sideroxylon puberlum, 3. Stillingia lineata, 4. Psidia terebinthina (both sites), 5.
Aphloia theiformis; animal species: 6. Stomorhina lunata, 7. Chaetocnema sp., 8.
Pachycerina crinicornis, 9. Apis mellifera, 10. Technomyrmex albipes.
5
Supplementary Material
Figure S1 The island of Mauritius (a) with the Black River Gorges National Park and
the study site Pétrin. The aerial photograph (b) shows Pétrin Conservation
Management Area (CMA, restored) and the unrestored site (control) in the study area.
10 Within the CMA (represented by the solid line), the study was conduced in the
rectangular part (separated by dashed line). Dotted lines indicate the arrangement of
the sampling transects.
Figure S2 Quantified pollination webs for plants and Hymenoptera pollinator
15 (excluding Formicidae) in (a) the restored and (b) the unrestored site. Visitor species
are shown as rectangles at the top and plant species are shown at the bottom. The
width of the rectangles reflects the relative abundance of flower visitors and plants.
Links represent interactions between species, and the width of the lines indicates the
relative quantitative visitation rate between an interacting pair of species. Webs are
20 drawn to the same scale. Colours represent the origin of animal species; green: native;
red: introduced; grey: unknown. Plant species highlighted in red are introduced. For
plant and animal codes see Appendices 2 and 3. 13 = Apis mellifera (honey bee).
40 Figure S3 Quantified pollination webs for plants and Dipteran pollinator in (a) the
restored and (b) the unrestored site. Visitor species are shown as rectangles at the top
and plant species are shown at the bottom. The width of the rectangles reflects the
relative abundance of flower visitors and plants. Links represent interactions between
5 species, and the width of the lines indicates the relative quantitative visitation rate
between an interacting pair of species. Webs are drawn to the same scale. Colours
represent the origin of animal species; blue: endemic; green: native; red: introduced;
grey: unknown. Plant species highlighted in red are introduced. For plant and animal
codes see Appendices II and III.
10
Figure S4 Quantified pollination webs for plants and lepidopteran pollinator in (a)
the restored and (b) the unrestored site. Visitor species are shown as rectangles at the
top and plant species are shown at the bottom. The width of the rectangles reflects the
relative abundance of flower visitors and plants. Links represent interactions between
15 species, and the width of the lines indicates the relative quantitative visitation rate
between an interacting pair of species. Webs are drawn to the same scale. Colours
represent the origin of animal species; blue: endemic; green: native; red: introduced;
grey: unknown. Plant species highlighted in red are introduced. For plant and animal
codes see Appendices II and III. 48 = Dysauxes florida; 98 = Nacoleia sp1.
20
Figure S5 Quantified pollination webs for plants and coleopteran pollinator in (a)
the restored and (b) the unrestored site. Visitor species are shown as rectangles at the
top and plant species are shown at the bottom. The width of the rectangles reflects the
relative abundance of flower visitors and plants. Links represent interactions between
25 species, and the width of the lines indicates the relative quantitative visitation rate
41 between an interacting pair of species. Webs are drawn to the same scale. Colours
represent the origin of animal species; blue: endemic; red: introduced; grey: unknown.
Plant species highlighted in red are introduced. For plant and animal codes see
Appendices II and III. 26 = Chaetocnema sp.
5 Figure S6 Quantified pollination webs for plants and ant pollinators (Formicidae) in
(a) the restored and (b) the unrestored site. Visitor species are shown as rectangles at
the top and plant species are shown at the bottom. The width of the rectangles reflects
the relative abundance of flower visitors and plants. Links represent interactions
10 between species, and the width of the lines indicates the relative quantitative visitation
rate between an interacting pair of species. Webs are drawn to the same scale. Colours
represent the origin of animal species; green: native; red: introduced; Plant species
highlighted in red are introduced. For plant and animal codes see Appendices II and
III.
15
Appendix I. Sampling methods.
Appendix II. Plant species at the restored site and the control site at Pétrin which
flowered between September 2003 and March 2004.
Appendix III Pollinator species observed on flowering plant species between
20 September 2003 and March 2004 at the restored site and the control site at Pétrin.
Appendix IV Interaction matrices of the restored and the control sites. Given values
are quantitative interaction rate between each interacting species pair. Zero indicates
that there was no interaction observed. Both networks shown in Figure 2 were drawn
from these matrices.
42 (a) 13 117 107 142 89 96 160 17 150 26 113 110 48 98 r i p a u b c g
m r r a a a l a v l n a a n i i o s a o a e e p r r o b a o l r o p r h o s l b h o o e e i p a e e a o o h o a e l i a n a e a g a i n t a u e o a l r i s v a b s m i l a e i t c m p s t l b m p r p a h m c e p c
c i r p i o o m e b e m z p p f r
n c v g p c o p c r f l b w f r
m l m b m
l l
c p s i
i a i e o o
y r i n c e c l a a n o y r g a e l a h o o o r a a a o h p m o a e r r r r u a u u u o o y a a l y y y y i y i i m h a u y o t a a s l a G A P B E S P C G P C P D D E A C S C C E C O G T T M W T T B B M S E S S S O O P P P P C G G C A E T E M D S M S S X X T F H P R F C S B L A C D E
(b) 13 117 142 107 96 56 160 17 150 26 48 110 98 p i a u c g a
m r a a a r a a i l a n n i o p s a o o a r r b l r o s p a h e l l o h o o o a e r o n r l e h i i m a a a v n n e u t a a i e l v a a o e b i e m m m p r p l t m a c m i t
a i e o z c p i i m
n r p o c c p g b c c c l r p p
f g f b t
r c
m m h m
l
s l p i c
i
i y a o o
l a a c r n o o i n a s r l y a o e o h r a u e o r u a p u l r r a r u u o a o y y y i i r r m y i m s a t l s s h a C T E S S S O P P C B C G C G S W S F C B A S P O R G M A E T D M D M L S S A H T O T B E F P D D C P C E C E W E X T H C C H A
30 Flower visitors per flower per hour 3 1 2 Flowers per m Figure 1
43 1
2
(a)
Restored
Unrestored
0 20 40 60 80 Number of species
(b)
Restored
Unrestored
0 10 20 30 40 50 60
Number of plant individuals (× 1000)
3 Endemic Native Introduced
4 Figure 2
44 10 (a)
restored 8 unrestored
6 F
r 4 e q u e n c y 2 1 2 3 3 4 5
0 0 10 20 30 40 Plant linkage (b) 60
20
15 F
r 10 e q u e n c y 5 8 6 6 7 9 10 0 0 10 20 30 40 1 Animal linkage
2 Figure 3
3
45 1
2 Figure S1 3 .
46 (a) 134 20 38 108 13 119 133 18 27 28 123 i u c g
a a n l a l i v o s e r p a r h a b r o i e h s a a o e a r e i t h n i u a n a i g e e a o b t p p o m m s p e e i w c t p b o o z h i s a r r v f p a m i c b
e f r n
m
l
l r
p c
s
i i
a
o o i
e e r a a l o e r r o o i o a a y y u p y m h t i i i a u u r e a a g y a u o s l a P W S P M L G E A S T T P S S S R P P M M H G G G E E E D C C C B B B A S S P O M F D C C P
(b) 5 27 36 13 119 13320 29 55 a l s o p l r h a o i o s i r e o a o e a a r l t l u h i t e a p o p m e c e v c a a v p p z a p f b t c c b
g f r
l
m
r
b
c p i
a o l c y r a o h a r i r r a o u e h y i s s r e o a i r n p a T H P S O O F C C T S P P M L G G E D D C C C B W D S R M H A A
5 flower visitors per flower per hour
2 flowers per cube
. (a) 66 106 25 77 90 105 120 136 148 158 9 15 42 45 47 68 78 114127 138140155 65 67 107 8 12 31 50 51 62 85 89 104 118147 156 16 41 56 72 88 96 103 112 128137 142 143 144 157 1 10 30 44 46 61 73 79 122 130139152 p r i a u c b g
r a a a a n n a l e l v o r e s p p o l h r a b o a o b i i e o r h e l s a o e a o p e r o a i n a h i a t a a l e t n e u a i p g o o b e r m p c p p m v i m a e s l c a m r p p o b o m h o z t p b s p f i i s v r g f a e b i
c c
r e f n
l m
m r l
l
l s
i
p c i
a
i o
o a l r e c c e a h i e r r o h a o a o o o o l u m m a a y h y u l a u s i r y y y a o u r e p n g t n a a y i i l a u o a E C P B S D P P G E P T P O M E P P M H G E D C C C X S S O D S C B R P O F F E E E D C C C B A G T L M G W T A A S A B G M S S S
(b) 67 31 51 70 88 95 106118 156 41 77 105 128 144 148 43 127 139 66 107 8 14 50 62 85 89 104 109147 25 56 72 90 96 103112 137 142 143 146 42 61 130152 p a r a a n n a l s p p o r i o l h a r o o l s a i a e l o e a a o r n l h a a l u e t m e a i p o v c e a m p e i p c a a v p z o t b p a m i f c c i p t g c b
n g f r
l
m
r l
b m l
i
p c
i
o o y l r a c a a o o i o l r e r r h u o m m h s s e y s u y y t i r p n a i o a a n r l r L C C P D O G G T P P O H F B T D F S T P E C C S E S S C M M S S M H E D C C A A R B S A D
5 flower visitors per flower per hour
2 flowers per cube
. (a) 111 4 11 154 141 58 75 126 135 48 2 21 49 63 64 69 76 86 102 110 115 159 6 74 97 98 99 124 129 145 u c r r a a a a n l l v o e s i e o o o a e i e s l h o a e o o r h n a u a e i e g a o t b o p r p e m c m s m p m i t b p c w p a s g f
c
b f r e
m
m
r
s c p
i
o i o c e e a a a i h r r o o h r o y a y i r n i p n i m u r a a a y g s o T O S D B P P M E A T S G A A C S C S E G E C G T R M C D G M P M C S G A P
(b) 64 86 115 19 59 48 63 76 102 110 153 58 60 74 98 99 135 c u r r a a a a l s i r o o a h o s r a e o a e o o r h u t e i l t e r p v a e o m c m m p p p m b t a t z i f p c
b
r g f
r m
l c
m
p i
a y c o a a i h r i o e r r r s o o t i s h y n r p n o e a a r S O D C T P M G S G S P P F T S C A T H E D C C A A W H C M G B
5 flower visitors per flower per hour
1 flower per cube
. (a) 22 40 71 93 131 87 7 26 24 52 92 113 132 u r a a l o e r p a o l r s o e r o n h t g e r b p o m p i e m a p t o a i c i
f e
m l m l
l i s
i o a e a l e o o l a r a r n p s r o u i y t T H C C C C G B E A G G A P C O M E M E P S S
(b)
23 37 40 54 93 100 131 87 7 26 22 24 39 53 92 94 113 132 i c g
r r a a a n a l s r i a i b p o o h l e h s e o a r o a n h a n l a n i t m p v i v m m o p a o e p c i t b m p p p c f c a i i
c g b n
f
l m
l
c
i
i
i
o
y c l a r a r o o o e a r o u m y s u a p n r i h a t s n a l a o a O M H E C C D T E M S P O L F F E C B A A E W S P H B G T S P C A G C H
5 flower visitors per flower per hour
1 flower per cube
. (a)
17 116 150 p i u a c g
r r m a a a n a n l l s e r p a p h o i b o l a r o s h e r e e o a e o o r a i h a t a n u t e g a e p p a o m e p c m s a m e c p i m o b p t a i h a r z p i o v c p b c l
n c e f r m
l l
m r
l
p i
s i
a
o i o r c a a l e o l a o o i a r m m u h s r r o o i u n n y y t a p y a i r o y e u a l y u a T G E P T S P H E C C C T T S O M M G G F E A A S S S R M E D D B A W S O C B P C S L D C C B X E
(b) 17 116 150 c r m a r a a a l l o i a h i l e s a l e o o o n i h n u m t a o v m v i a p m m z p i p p t a r c i g c b
f
m
l
p i
o o y r u o o r o a o y e n h s r a y y t i a a p o u T S G B A P T P M T R M H E D C C B S S S S M H B C A
5 flower visitors per flower per hour
2 flowers per cube
. . Supplementary Methods
Kaiser-Bunbury, Memmott, and Müller
Appendix I: Additional methods
Flower counts
Fortnightly flower counts started in calendar week 37 (15th September 2003) and
finised in week 9 (15th March 2004). Counts were always carried out at the beginning
of each fortnight. Two metre cubes were placed randomly within each 20 m transect
section. We used a 1×1×1 m wooden frame to mark the cube in which flowers were
counted. Plants within 2.5 m on either side of the transect were included in the flower
counts. We counted the number of floral units in a total of 230 cubic meters for each
site and fortnight. One floral unit was defined as one individual flower or a group of
flowers in the case of composite flowerheads. The mean number of flowers per floral
unit for composite species was calculated by averaging the number of flowers from 20
randomly selected floral units from different individuals. Only four plant species
included in this study displayed multiple open flowers per floral unit (Flagellaria
indica L., Flagellariaceae, mean flowers per floral unit = 12.0; Stillingia lineata ssp.
lineata Müll. Arg., Euphorbiaceae, 11.0; Helichrysum proteoides Baker, 3.9; Psiadia
terebinthina Scott, both Asteraceae, 4.0), and hereafter we use ‘flowers’ instead of
‘floral unit’. Some rare plant species (site 1 = 5 spp, site 2 = 7 spp) were not
represented in the random counts along transects. For those species we counted the
number of flowers per cube on one flowering individual each fortnight and took the
average of those readings as a measure of floral abundance.
Pollinator observations
We observed pollinators for a total of 858.5 hours (site 1 = 471 h, site 2 =
387.5 h). Observation units were temporally and spatially evenly arranged. Flower
visitors were observed only during dry conditions. During the wet season (December– Kaiser-Bunbury, Memmott, and Müller
April) heavy showers frequently interrupted observation sessions, which were then suspended and continued about 30 min after the rain had stopped to allow pollinators to re-emerge. We conducted pollinator observations during daylight from 6 am – 6 pm.
Eight plant species at site 1 and five plant species at site 2 (mainly Rubiaceae) were identified as potentially attracting nocturnal pollinators such a microlepidoptera or hawkmoths. Those plant species were observed for one hour during the day and one hour during night (from 8 pm – 12 pm) in each fortnight. For night-time observations, we used head-lights with red filters to minimise disturbance or attraction to potential pollinators (Kearns and Inouye, 1993). Bats were never observed to visit flowers in
Pétrin.
We recorded the identity of all flower visitors which touched the sexual parts of flowers and which therefore potentially contributed to pollination. Here, we use the terms ‘flower visitor’ and ‘pollinator’ synonymously. An ‘interaction’ was defined as a link between a plant and an animal species, while a ‘visit’ described a link between a plant and an animal individual. Pollinators were collected from flowers for later identification when identification by sight alone was not possible. Birds, geckos and butterflies could be reliably identified in the field by using field guides (e.g. Williams,
1989). Other insects were collected, mounted and identified to species or genus level by taxonomists at various institutions (see Appendix II). In total, approximately 50% of all animal species could be reliably identified to species level.
Abundance measures such as floral and plant abundance, and quantitative visitation rate were ln-transformed to reach normality or, if entered as explanatory variable in the model, to obtain a fit of the model, which described best the relationship between variables. Linear mixed effects models were used to : firstly, to describe the difference Kaiser-Bunbury, Memmott, and Müller in the relationship of floral and plant abundance between the sites. Plant abundance
(ln-transformed) was entered as the response variable, floral abundance and site as fixed effects and plant species identity as a random effect; secondly, to test whether visitation rate of a plant species is dependent on its abundance, where the visitation rate was natural (log +1)-transformed, plant abundance and site were entered as fixed effects and plant species identity was entered as random effect; and thirdly, to test whether plant species linkage was related to the total number of visits received. The explanatory variable Site was entered first into the model to filter out the site effect before calculating other main effects, and to account for dependences within plant species, plant identity was included in the model as random effect.
LITERATURE CITED
Kearns, C.A., Inouye, D.W., 1993. Techniques for pollination biologists. University
Press of Colorado, Niwot.
Williams, J.R., 1989. Butterflies of Mauritius. Precigraph Ltd. , Pailles, Mauritius. Supplementary Table
Kaiser-Bunbury, Memmott, and Müller
Appendix II. Plant species at the restored site (R = 74 species) and the control site (C = 64 species) at Pétrin which flowered between
September 2003 and March 2004. The species belong to 38 families. Presented are plant species code (corresponding to coding of the visitation
webs), origin (E = endemic, N = native, I = Introduced) and status of species (IUCN criteria, CR = Critically endangered, EN = endangered, VU
= vulnerable, LC = least concern, – = no status available), number of plant individuals (plant abundance), number of attracted pollinator species
(lp = linkage), and number of visits/flower/hour (visitation rate).
Plant No. Floral Visitation Site Plant family Plant species Origin Status l code plants abundance p rate
R Annonaceae Xylopia lamarckii Xy la E CR 22 0.0006 1 0.222 C 2 0.0003 0 0 R Apocynaceae Tabernaemontana persicariaefolia Ta per E EN 39 0.053 5 0.290 C 6 0.007 3 0.165 R Araliaceae Polyscias mauritiana Po ma E CR 2 0.006 6 0.671 R Asteraceae Faujasiopsis flexuosa ssp erecta Fa fl E VU 435 0.025 4 0.061 C 164 0.004 9 0.649 R Helichrysum proteoides He pr E EN 12 0.213 8 0.244 Kaiser-Bunbury, Memmott, and Müller
C Asteraceae Helichrysum proteoides He pr E EN 12 0.297 14 0.438 R Psiadia terebinthina Psi te E VU 253 1.672 38 0.563 C 155 0.484 38 0.568 R Bignoniaceae Colea colei Co co E EN 2 0.003 0 0 R Rousseaceae Roussea simplex Ro si E EN 3 0.015 12 1.893 R Celastraceae Pleurostylia leucocarpa Pl le E EN 3 0.003 8 0.291 R Chrysobalanaceae Grangeria borbonica Gr bo N VU 3 0.009 10 0.220 C 7 0.009 14 0.509 R Clusiaceae Calophyllum eputamen var eputamen Ca ep E VU 264 0.008 11 0.521 C 32 0.011 4 0.390 C Harungana madagascariensis Ha ma I – 8 0.010 3 1.308 R Dracaenaceae Dracaena reflexa var angustifolia Dr re N LC 28 0.035 13 0.526 C 3 0.003 13 0.625 R Ebenaceae Diospyros revaughanii Di re E VU 29 0.005 9 1.256 C 3 0.001 3 0.698 R Ericaceae Agauria salicifolia Ag sa N LC 8 0.020 7 0.170 R Erythroxylaceae Erythroxylum macrocarpum Er ma E VU 103 0.036 27 0.622 C 35 0.022 29 1.206 R Euphorbiaceae Antidesma madagascariense An ma N LC 7 0.013 13 0.278 Kaiser-Bunbury, Memmott, and Müller
C Euphorbiaceae Antidesma madagascariense An ma N LC 2 0.075 5 0.222 R Claoxylon linostachys ssp brachyphyllum Cl li E CR 11 0.167 18 0.138 C 1 0.013 4 0.140 R Cordemoya integrifolia Co in N LC 46 0.054 4 0.115 C 8 0.009 3 0.103 R Croton fothergillifolius Cr fo E CR 77 0.358 29 0.349 C 46 0.049 28 0.995 C Croton grangeroides Cr gr E EN 57 0.026 12 0.303 C Homalanthus populifolius Ho po I – 67 0.035 18 1.131 R Phyllanthus phillyreifolius var telfairianus Ph ph E VU 22 0.593 7 0.168 C 7 0.045 10 0.207 R Stillingia lineata ssp lineata St li N LC 283 0.112 36 3.098 C 234 0.059 33 4.797 R Flacourtiaceae Aphloia theiformis Ap th N LC 1586 0.940 39 1.429 C 877 0.279 28 0.799 R Casearia coriacea Ca co N VU 292 0.040 2 0.675 C 174 0.002 4 0.597 Erythrospermum monticolum var R Er mo E VU 20 0.023 9 0.117 monticolum C 1 0.002 0 0 Kaiser-Bunbury, Memmott, and Müller
R Flagellariaceae Flagellaria indica Fl in N LC 6 0.082 8 0.015 C 8 0.030 2 0.112 R Lauraceae Ocotea laevigata Oc la E EN 74 0.051 5 0.106 R Loganiaceae Geniostoma borbonicum Ge bo E VU 24 0.077 23 1.226 R Loranthaceae Bakerella hoyifolia ssp bojeri Ba ho N EN 2 0.001 3 0.491 R Malvaceae Trochetia blackburniana Tr bl E EN 89 0.004 1 0.077 C 19 0.001 2 0.893 C Melastomataceae Clidemia hirta Cl hi I – 3 0.001 0 0 R Memecylon ovatifolium Me ov E VU 11 0.015 8 0.183 C Ossaea marginata Os ma I – 223 0.176 0 0 R Tristhema mauritiana Tr ma N LC 4 0.000 1 0.500 C 12 0.001 2 0.300 R Warneckea trinervis Wa tr E VU 48 0.205 8 0.270 C 27 0.024 2 0.030 R Meliaceae Turraea rigida Tu ri E CR 11 0.020 4 0.134 C 5 0.001 1 0.101 R Monimiaceae Tambourissa peltata Ta pe E EN 32 0.002 4 0.857 C Myrsinaceae Ardisia crenate Ar cr I – 36 0.005 0 0 R Badula insularis Ba in E EN 2 0.020 9 0.372 Kaiser-Bunbury, Memmott, and Müller
C Myrsinaceae Badula insularis Ba in E EN 2 0.003 2 0.439 R Badula platiphylla Ba pl E CR 10 0.006 6 0.304 C 7 0.004 5 0.493 R Embelia angustifolia Em an N EN 18 0.055 5 0.431 C 3 0.003 6 0.107 R Myrtaceae Eugenia orbiculata Eu or E VU 7 0.001 4 0.824 C 30 0.001 1 0.125 R Monimiastrum globosum Mo gl E VU 15 0.001 8 0.647 C Psidium cattleianum Ps ca I – 49626 0.264 11 0.622 R Syzygium commersonii Sy com E VU 4 0.001 2 0.219 C 2 0.002 3 0.318 R Syzygium coriaceum Sy cor E VU 475 0.170 18 0.679 C 345 0.119 10 0.368 R Syzygium glomeratum Sy gl E VU 135 0.003 9 0.602 C 113 0.010 3 0.156 R Syzygium mauritianum Sy ma E EN 12 0.001 2 0.116 R Syzygium petrinense Sy pe E EN 113 0.052 6 0.384 C 10 0.007 8 0.241 R Syzygium venosum Sy ve E EN 9 0.001 5 1.784 Kaiser-Bunbury, Memmott, and Müller
R Ochnaceae Ochna mauritiana Oc ma E VU 150 0.161 5 0.059 C 166 0.139 16 0.951 R Oleaceae Olea lancea Ol la N LC 541 0.071 9 0.118 C 570 0.073 5 0.359 14.80 R Pandanaceae Pandanus barklyi var barklyi Pa ba E EN 12 0.006 5 0 R Pandanus rigidifolius Pa ri E CR 9 0.001 3 0.462 R Pandanus wiehii Pa wi E EN 21 0.028 3 0.600 R Pittosporaceae Pittosporum senacia Pi se N LC 52 0.001 14 0.868 C 5 0.002 0 0 C Rosaceae Rubus alcefolius Ru al I – 68 0.007 4 0.813 R Rubiaceae Antirhea borbonica An bo N LC 1651 0.723 10 0.157 C 1157 0.952 10 0.116 R Bertiera zaluzania Be za E VU 33 0.034 11 0.430 C 5 0.008 12 1.467 R Chassalia coriacea var coriacea Ch co E EN 118 0.113 10 0.228 C 20 0.026 7 0.341 R Chassalia petrinensis Ch pe E CR 2 0.002 4 0.667 R Coffea macrocarpa Co mac E VU 34 0.018 12 0.597 C 21 0.019 4 0.184 Kaiser-Bunbury, Memmott, and Müller
R Rubiaceae Coffea mauritiana Co mau N VU 3 0.006 14 1.088 C 6 0.007 1 0.036 R Gaertnera petrinensis Ga pe E EN 102 0.055 7 0.188 R Gaertnera psychotrioides/edentata1 Ga ps E EN 732 0.173 16 0.480 C 196 0.107 17 0.455 R Gaertnera rotundifolia Ga ro E CR 91 0.037 6 0.188 C 16 0.020 1 0.048 C Myonima violacea var ovata My vi E VU 23 0.119 13 0.574 C Psathura terniflora Ps te E VU 5 0.001 2 4.000 R Pyrostria fasciculata Py fa E EN 24 0.004 5 0.853 R Rutaceae Euodia chapelieri var chapelieri Eu ch N EN 6 0.110 8 0.060 Euodia obtusifolia ssp gigas var Eu ob R E CR 10 0.001 4 0.048 brachypoda br Eu ob R Euodia obtusifolia ssp gigas var gigas N CR 2 0.041 6 0.185 gi C 1 0.000 1 0.308 R Toddalia asiatica To as N LC 4 0.022 28 0.747 C 2 0.008 15 1.678 R Sapindaceae Dodonaea viscosa Do vi N LC 18 0.193 2 0.025 C 50 0.062 19 0.169 R Sapindaceae Doratoxylon apetalum var apetalum Do ap N VU 230 0.010 4 0.688 Kaiser-Bunbury, Memmott, and Müller
ap Do ap C Doratoxylon apetalum var diphyllum N VU 7 0.005 2 1.000 di R Molinaea alternifolia Mo al N VU 305 0.073 28 1.487 C 184 0.083 19 1.238 C Molinaea macrantha Mo ma E VU 3 0.005 3 0.431 R Sapotaceae Labourdonnaisia calophylloides La ca N VU 307 0.131 6 0.398 C 196 0.081 5 0.378 R Mimusops erythroxylon Mi er E VU 173 0.029 10 0.495 R Sideroxylon cinereum Si ci E VU 265 0.020 21 1.377 C 360 0.567 31 1.005 R Sideroxylon puberulum Si pu E VU 594 0.041 33 0.351 C 457 0.723 13 0.914 R Smilacaceae Smilax anceps Sm an N LC 36 0.004 4 0.053 C 26 0.010 1 0.014 C Thymelaeaceae Wikstroemia indica Wi in I – 2027 0.346 1 0.041 R Xyridaceae Xyris sp Xy sp N – 22 0.018 2 0.063
1 Gaertnera psychotrioides and G. edentata are indistinguishable in the field Supplementary Table
Kaiser-Bunbury, Memmott, and Müller
Appendix III. Pollinator species observed on flowering plant species between September 2003 and March 2004 at the restored site
(R = 135 species) and the control site (C = 100 species) at Pétrin. Presented are species code (corresponding to coding of the visitation
webs), the species origin (E = endemic, N = native, I = introduced, Un = unknown), the number of visits (total number of visits
oberserved = 7295), the mean number of probed flowers per visit (± SE) and the number of visited plant species (la = linkage).
Anim al No. of Probed flowers Site Animal order Animal family Animal species code Origin visits (mean ± SE) la R Coleoptera Cerambycidae Cerambycidae sp 1 22 Un 2 1.50 ± 0.50 2 U 4 2.25 ± 0.25 2 U Cerambycidae sp 2 23 Un 1 1.00 1 R Cerambycidae sp 3 24 Un 2 1.00 ± 0.00 2 U 1 2.00 1 R Mauritiborium undulatus 87 E 4 2.25 ± 0.25 3 U 14 1.71 ± 0.30 6 R Chrysomelidae Chaetocnema sp 26 I 94 1.64 ± 0.12 15 U 702 1.73 ± 0.05 34 U Cryptocephalinae sp 39 Un 1 1.00 1 R Eumolpinae sp 1 52 Un 1 1.00 1 U Eumolpinae sp 2 53 Un 1 2.00 1 U Eumolpinae sp 3 54 Un 5 1.80 ± 0.20 2 R Coccinellidae Hyperaspis hottentota 71 Un 1 2.00 1 R Cucujidae Ahasverus advena 7 I 8 1.50 ± 0.19 5 U 14 2.21 ± 0.32 5 U Curculionidae Cratopus psittacus 37 Un 1 7.00 1 Kaiser-Bunbury, Memmott, and Müller
R Coleoptera Melyridae Dasytinae sp 40 Un 1 1.00 1 U 1 3.00 1 R Pelecophora intemipta 113 Un 9 2.33 ± 0.65 4 U 5 2.00 ± 0.32 3 R Mordellidae Mordellidae sp 1 92 Un 6 1.17 ± 0.17 2 U 1 3.00 1 R Mordellidae sp 2 93 Un 1 1.00 1 U 1 3.00 1 U Mordellidae sp 3 94 Un 1 1.00 1 U Nitidulidae Nitidulidae sp 100 Un 1 1.00 1 R Scirtidae Scirtidae sp 1 131 Un 1 1.00 1 U 1 3.00 1 R Scirtidae sp 2 132 Un 1 1.00 1 U 1 1.00 1 R Diptera Acalyptrate Acalyptrate sp 1 Un 3 2.00 ± 0.58 1 R Agromyzidae Melanagromyza sojae 88 I 5 4.00 ± 1.05 4 U 1 2.00 1 R Anthomyiidae Anthomyia faciata 12 N 1 2.00 1 R Bombyliidae Villa unifasciata 156 N 68 3.06 ± 0.24 19 U 51 1.96 ± 0.16 17 R Calliphoridae Chrysomya megacephala 31 N 129 5.16 ± 0.50 27 U 67 5.31 ± 0.78 17 R Stomorhina lunata 142 I 444 4.81 ± 0.25 35 U 225 5.87 ± 0.39 30 R Chironomidae Chironomidae sp 30 Un 1 1.00 1 R Dolichopodidae Dolichopodidae sp 44 Un 2 1.00 ± 0.00 1 R Drosophilidae Drosophila sp 1 45 Un 1 1.00 1 Kaiser-Bunbury, Memmott, and Müller
R Diptera Drosophilidae Drosophila sp 2 46 Un 2 1.00 ± 0.00 1 R Drosophila sp 3 47 Un 5 1.6 ± 0.24 2 R Zaprionus tuberculatus 157 I 3 1.00 ± 0.00 1 R Zaprionus vittiger 158 I 1 1.00 1 R Ephydridae Hyadina sp 68 Un 2 3.00 ± 1.00 2 R Psilopa iceryae 120 I 26 2.27 ± 0.36 11 R Fanniidae Fannia pusio 56 I 95 3.41 ± 0.21 11 U 121 3.12 ± 0.20 11 R Lauxaniidae Homoneura quadrivittata 65 E 2 1.00 ± 0.00 1 R Homoneura sp 1 66 E 1 1.00 1 U 1 6.00 1 R Homoneura sp 2 67 E 5 2.40 ± 1.17 2 U 1 3.00 1 R Lauxania sp 73 Un 1 1.00 1 R Pachycerina crinicornis 107 E 288 3.03 ± 0.14 35 U 87 2.91 ± 0.27 21 R Sapromyza sp near nudiuscula 127 Un 9 4.33 ± 1.41 5 U 4 1.50 ± 0.29 4 R Limoniidae Limonia (Dycranomia) sp 78 Un 1 1.00 1 R Limoniidae sp 79 Un 1 2.00 1 U Muscidae Atherigona orientalis 14 N 1 2.00 1 R Atherigona sp 15 Un 1 3.00 1 R Graphomya maculata 62 N 18 2.67 ± 0.89 7 U 1 1.00 1 U Hydrotaea fuliginosa 70 N 2 3.00 ± 0.00 1 R Limnophora quaterna 77 I 4 1.75 ± 0.25 2 U 1 1.00 1 Kaiser-Bunbury, Memmott, and Müller
U Diptera Muscidae Musca confiscate 95 N 1 3.00 1 R Musca domestica 96 I 133 3.35 ± 0.30 23 U 132 4.98 ± 0.57 20 R Ophyra capensis 103 I 24 3.33 ± 0.48 8 U 33 5.67 ± 1.05 8 R Orchisia costata 104 N 2 1.00 ± 0.00 2 U 2 2.00 ± 1.00 2 R Orthellia albigena 106 N 9 4.00 ± 1.21 7 U 13 2.69 ± 0.56 3 R Spilogona sp 140 Un 1 2.00 1 R Stomoxys calcitrans 143 I 48 2.10 ± 0.31 13 U 38 4.32 ± 0.68 10 R Stomoxys niger 144 I 47 1.98 ± 0.32 10 U 22 2.50 ± 0.35 7 R Mycetophilidae Lygistorrhina sp 85 N 43 5.58 ± 0.66 9 U 56 3.61 ± 0.55 11 R Sarcophagidae Sarcophaga arno 128 I 9 5.00 ± 1.27 6 U 9 3.00 ± 1.04 7 R Scatopsidae Scatopsidae sp 130 Un 1 3.00 1 U 1 2.00 1 R Sepsidae Sepsis lateralis 136 I 10 4.10 ± 1.03 3 R Simuliidae Simulium (Byssodon) sp 2 137 I 1 6.00 1 U 1 1.00 1 R Simulium sp 138 Un 1 2.00 1 R Syrphidae Allograpta nasuta 8 N 42 3.74 ± 0.62 20 U 63 4.48 ± 0.56 20 R Allograpta sp 1 9 Un 1 3.00 1 Kaiser-Bunbury, Memmott, and Müller
R Diptera Syrphidae Allograpta sp 2 10 Un 4 3.75 ± 1.80 1 R Episyrphus sp near circularis 50 N 24 4.38 ± 0.98 13 U 22 2.50 ± 0.55 12 R Eristalinus flaveolus 51 N 51 3.35 ± 0.34 18 U 27 4.22 ± 0.80 11 R Ischiodon aegyptius 72 I 21 3.43 ± 0.69 12 U 17 3.88 ± 1.37 7 R Melanostoma annulipes 89 N 72 1.88 ± 0.21 12 U 35 1.91 ± 0.20 10 R Melanostoma bituberculatum 90 I 14 4.14 ± 0.63 6 U 10 4.30 ± 1.05 6 R Ornidia obesa 105 I 21 2.76 ± 0.56 13 U 8 6.00 ± 1.43 8 R Paragus borbonicus 112 I 75 4.80 ± 0.55 21 U 15 4.13 ± 1.44 9 U Syritta bulbus 146 I 4 3.00 ± 0.41 1 R Syritta nigrofemorata 147 N 16 3.94 ± 0.76 8 U 17 3.94 ± 0.82 8 R Syritta sp near abyssinica 148 I 10 3.80 ± 0.90 7 U 6 3.83 ± 1.08 3 U Tachinidae Palexorista sp 109 N 1 2.00 1 R Peribaea sp 114 Un 1 5.00 1 R Phorinia sp 118 N 59 3.66 ± 0.29 12 U 10 1.80 ± 0.33 5 R Siphona sp 139 Un 3 1.33 ± 0.33 2 U 1 4.00 1 R Thelairodrino sp 152 Un 1 3.00 1 Kaiser-Bunbury, Memmott, and Müller
U Diptera Tachinidae Thelairodrino sp 152 Un 1 1.00 1 R Tephritidae Bactrocera cucurbitae 16 I 2 1.50 ± 0.5 2 R Ceratitis roas 25 I 5 2.40 ± 0.40 3 U 1 1.00 1 R Dioxyna sororcula 41 I 11 2.73 ± 0.14 5 U 25 3.12 ± 0.37 7 R Goniurellia or Dectodes sp 61 Un 9 3.44 ± 0.75 3 U 2 2.00 ± 0.00 1 R Trirhithrum sp near nigerrimum 155 Un 7 2.14 ± 0.26 3 R Unknown Diptera sp 1 42 Un 7 3.57 ± 0.61 1 U Diptera sp 2 43 Un 1 2.00 1 U Diptera sp 3 42 Un 1 2.00 1 R Hemiptera Cicadellidae Acopsis viridicans 3 N 4 1.75 ± 0.25 3 R Cicadellidae sp 32 Un 1 1.00 1 U Cixiidae Cixiidae sp 1 33 Un 1 3.00 1 U Cixiidae sp 2 34 Un 1 1.00 1 R Lygaeidae Lygaeidae sp 1 80 Un 1 2.00 1 U Lygaeidae sp 2 81 Un 1 5.00 1 U Lygaeidae sp 3 82 Un 1 1.00 1 R Lygaeidae sp 4 83 Un 1 3.00 1 R Lygaeidae sp 5 84 Un 13 2.31 ± 0.50 3 U 22 3.09 ± 0.38 1 R Miridae Miridae sp 91 Un 5 1.40 ± 0.24 4 U 1 8.00 1 R Nogodinidae Nogodinidae sp 101 Un 5 2.00 ± 0.45 1 R Psyllidae Psyllidae sp 1 121 Un 1 1.00 1 R Psyllidae sp 2 122 Un 1 1.00 1 Kaiser-Bunbury, Memmott, and Müller
U Hemiptera Psyllidae Psyllidae sp 2 122 Un 1 1.00 1 R Ricaniidae Tarundia servillei 149 Un 5 1.80 ± 0.37 4 R Tettigoniidae Conocephalus sp 1 35 Un 1 1.00 1 R Tettigoniidae sp 1 151 Un 1 1.00 1 R Hymenoptera Apidae Apis mellifera 13 I 645 6.94 ± 0.27 43 U 682 8.80 ± 0.35 28 U Braconidae Agathidinae sp 5 Un 1 5.00 1 R Cheloninae sp 1 27 Un 2 1.50 ± 0.50 1 U 3 3.67 ± 0.67 1 R Cheloninae sp 2 28 Un 1 2.00 1 U Cheloninae sp 3 29 Un 2 1.00 1 U Cotesia sp 1 36 Un 3 1.33 ± 0.33 1 R Calcidoidae Calcidoidae sp 1 18 Un 1 3.00 1 R Colletidae Paleorhiza sp 1 108 N 1 3.00 1 U Eurytonidae Eurytonidae sp 1 55 Un 1 3.00 1 R Formicidae Brachymyrmex sp 17 N 228 1.83 ± 0.12 20 U 96 1.92 ± 0.10 12 R Pheidole megacephala 116 I 16 1.69 ± 0.15 1 U 3 2.00 ± 0.00 1 R Technomyrmex albipes 150 I 456 2.05 ± 0.08 45 U 236 2.10 ± 0.08 24 R Ichneumonidae Campopleginae sp 20 Un 1 4.00 1 U 2 2.00 ± 0.00 1 R Cryptinae sp 38 Un 1 1.00 1 R Pteromalidae Pteromalidae sp 123 Un 3 2.00 ± 0.58 1 R Scoliidae Scolia carniflex 133 I 1 3.00 1 U 1 9.00 1 Kaiser-Bunbury, Memmott, and Müller
R Hymenoptera Scoliidae Scolia oryctophaga 134 I 1 11.00 1 R Vesperidae Polistes hebraeus 119 I 42 4.71 ± 0.60 13 U 34 4.68 ± 0.66 13 R Lepidoptera Arctiidae Dysauxes florida 48 E 5 1.8 ± 0.37 3 U 163 6.52 ± 0.52 18 R Eilema squalida 49 N 4 4.75 ± 0.75 2 R Nyctemera insulare 102 N 3 1.33 ± 0.33 2 U 1 7.00 1 R Crambidae Nacoleia sp 1 98 Un 252 2.37 ± 0.15 24 U 78 2.24 ± 0.20 20 R Nacoleia sp 2 99 Un 15 1.87 ± 0.17 7 U 19 1.84 ± 0.37 5 R Scopariinae sp 135 Un 3 2.00 ± 0.58 2 U 2 1.00 ± 0.00 2 R Gelechiidae Gelechioidea sp 1 58 Un 2 2.00 ± 0.00 2 U 1 4.00 1 U Gelechioidea sp 2 59 Un 16 2.00 ± 0.22 5 U Gelechioidea sp 3 60 Un 2 1.50 ± 0.50 2 R Hesperiidae Panara naso 110 N 31 2.55 ± 0.34 13 U 31 3.19 ± 0.33 11 R Hypsidae Aganais borbonica 4 N 1 2.00 1 R Lecithoceridae Lecithoceridae sp 1 74 Un 6 1.83 ± 0.31 4 U 3 1.67 ± 0.67 3 R Lecithoceridae sp 2 75 Un 3 1.67 ± 0.33 3 R Lycaenidae Leptotes pirithous 76 N 16 3.06 ± 0.64 8 U 76 N 14 4.00 ± 0.62 5 R Zizeeria knysa 159 N 1 2.00 1 Kaiser-Bunbury, Memmott, and Müller
R Lepidoptera Macroglossidae Macroglossum milvus 86 N 6 16.3 ± 5.28 2 U 2 4.50 ± 2.50 2 R Noctuidae Achaea finite 2 N 1 5.00 1 R Agrostis atritegulator 6 Un 1 6.00 1 R Condica capensis 11 N 1 1.00 1 R Hydrillodes sp 69 N 8 1.25 ± 0.16 2 R Mythimna sp 97 Un 1 2.00 1 R Remigia frugalis 126 Un 1 2.00 1 R Sarrothripinae sp 129 Un 1 2.00 1 R Spodoptera littoralis 141 I 1 6.00 1 R Strictopterinae sp 145 Un 1 2.00 1 U Thysanoplusia orichalcea 153 N 1 3.00 1 R Trichoplusia indicator 154 N 4 4.75 ± 1.89 2 R Nymphalidae Henotesia narcissus 63 N 26 2.00 ± 0.21 9 U 4 3.50 ± 1.32 2 R Phalanta phalantha 115 N 1 6.00 1 U 1 1.00 1 R Papillionidae Papillio manlius 111 E 1 7.00 1 U Pieridae Calopsilia florella 19 I 1 1.00 1 R Pterophoridae Pterophoridae sp 124 Un 1 1.00 1 R Sphingidae Cephonodes trochilus 21 N 6 8.17 ± 4.83 4 R Hippotion eson 64 N 8 12.1 ± 4.81 3 U 1 1.00 1 R Passeriformes Ploceidae Foudia madagascariense 57 I 1 106.00 1 R Pycnonotidae Pycnonotus jocosus 125 I 1 37.00 1 R Zosteropidae Zosterops mauritianus 160 E 31 10.9 ± 3.11 8 U 3 4.00 ± 0.58 2 Kaiser-Bunbury, Memmott, and Müller
R Squamata Gekkonidae Phelsuma cepediana 117 E 44 6.93 ± 1.29 12 U 5 4.60 ± 2.46 3
1 Insects were identified to species or genus level by taxonomists (Diptera: J. C. Deeming, National Museum of Wales; Coleoptera, except Cerambycidae: B. Levey, National Museum of Wales, UK; Cerambycidae: K. Adlbauer, Landesmuseum Joanneum Graz,
Austria; Collitidae: N. Springate, Natural History Museum London, UK; Parasitic Hymenoptera: D. Quicke, Imperial College Silwood
Park, UK; Microlepidoptera: D. Slade, National Museum of Wales, UK; Microlepidoptera: W. Speidel, Alexander Koenig Research
Institute and Museum of Zoology Bonn, Germany; Macrolepidoptera: S. Couteyen, Réunion; Macrolepidoptera, Sphingidae,
Hemiptera: J. Williams and S. Ganeshan, Mauritius Sugar Industry Research Institute MSIRI, Mauritius; Formicidae: L. Lach,
Murdoch University, Australia) Supplementary Network Matrices
Appendix IV Interaction matrices of the restored and the control site. Given values are quantitative interaction rate between each interacting species pair. Zero indicates that there was no interaction observed. All networks shown in Figure 1 and supplementary figures S2-S6 were drawn from these matrices.