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Recent decades have seen a surge in awareness about insect pollinator declines. Social bees receive the most attention, but most flower-visiting species are lesser known, non-bee insects. Nocturnal flower visitors, e.g. moths, are especially difficult to observe and largely ignored in pollination studies. Clearly, achieving balanced monitoring of all pollinator taxa represents a major scientific challenge. Here, we use time-lapse cameras for season-wide, day-And-night pollinator surveillance of Trifolium pratense (L.; red clover) in an alpine grassland. We reveal the first evidence to suggest that moths, mainly Noctua pronuba (L.; large yellow underwing), pollinate this important wildflower and forage crop, providing 34% of visits (bumblebees: 61%). This is a remarkable finding; moths have received no recognition throughout a century of T. pratense pollinator research. We conclude that despite a non-negligible frequency and duration of nocturnal flower visits, nocturnal pollinators of T. pratense have been systematically overlooked. We further show how the relationship between visitation and seed set may only become clear after accounting for moth visits. As such, population trends in moths, as well as bees, could profoundly affect T. pratense seed yield. Ultimately, camera surveillance gives fair representation to non-bee pollinators and lays a foundation for automated monitoring of species interactions in future., Biology Letters, 18 (7), ISSN:1744-9561, ISSN:1744-957X

Honey bees are key insect pollinators, providing important economic and ecological value for human beings and ecosystems. This has triggered the development of several monitoring methods for assessing the temporal development of colony size, food storage, brood and pathogens. Nonetheless, most of these methods are based on visual assessments that are observer-dependent and prone to bias. Furthermore, the impact on colony development (invasiveness), as well as accuracy, were rarely considered when implementing new methods. In this study, we present and test a novel accurate and observer-independent method for honey bee colony assessment, capable of being fully standardized. Honey bee colony size is quantified by assessing the weight of adult bees, while brood and provision are assessed by taking photos and conducting image analysis of the combs with the image analysis software Deepbee®. The invasiveness and accuracy of the method were investigated using field data from two experimental apiaries in Portugal, comparing results from test and control colonies. At the end of each field experiment, most of the tested colonies had the same colony size, brood levels and honey production as the control colonies. Nonetheless, continuous weight data indicated some disturbance in tested colonies in the first year of monitoring. The overall accuracy of the image analysis software was improved by training, indicating that it is possible to adapt the software to local conditions. We conclude that the use of this fully quantitative method offers a more accurate alternative to classic visual colony assessments, with negligible impact on colony development. Honey bees are key insect pollinators, providing important economic and ecological valuefor human beings and ecosystems. This has triggered the development of several monitoringmethods for assessing the temporal development of colony size, food storage, broodand pathogens. Nonetheless, most of these methods are based on visual assessments thatare observer-dependent and prone to bias. Furthermore, the impact on colony development(invasiveness), as well as accuracy, were rarely considered when implementing new methods.In this study, we present and test a novel accurate and observer-independent method forhoney bee colony assessment, capable of being fully standardized. Honey bee colony size isquantified by assessing the weight of adult bees, while brood and provision are assessed bytaking photos and conducting image analysis of the combs with the image analysis softwareDeepbeeVR . The invasiveness and accuracy of the method were investigated using field datafrom two experimental apiaries in Portugal, comparing results from test and control colonies.At the end of each field experiment, most of the tested colonies had the same colony size,brood levels and honey production as the control colonies. Nonetheless, continuous weightdata indicated some disturbance in tested colonies in the first year of monitoring. The overallaccuracy of the image analysis software was improved by training, indicating that it ispossible to adapt the software to local conditions. We conclude that the use of this fullyquantitative method offers a more accurate alternative to classic visual colony assessments,with negligible impact on colony development.

The socioeconomically important fruit tree Parkia biglobosa is becoming less abundant in the West African savannah, possibly due to poor regeneration. This decline can be self-enforcing if lower densities of fertile trees result in increasing self-pollination followed by increased abortion rates or poor regeneration due to inbreeding depression. Hence, we have studied the reproductive success and seedling viability of P. biglobosa after controlled self- and cross-pollination based on a full diallel crossing design with eight trees. Controlled cross-pollination tripled the pod set compared to open-pollinated capitula, suggesting that fruiting of P. biglobosa trees in the study area is already seriously pollen limited. Self-pollination and specific pairs of trees resulted in very few pods, suggesting a high level of self-incompatibility. Cross-pollination resulted in larger pods with more and heavier seeds than self-pollinated pods. The total amount of sugar in the fruit pulp was correlated with both the number of healthy and total seeds per pod. Growth rate of self-pollinated seedlings was lower than the cross-pollinated ones, suggesting significant inbreeding depression. Because the wild fruit trees play an important role in human nutrition, these results give rise to serious concerns. We recommend that future studies investigate how the level of cross-pollination can be increased and how the regeneration of P. biglobosa, whether natural or planted, can be improved.

2017-2018 Belmont Forum and BiodivERsA joint call for research proposals, under the BiodivScen ERA-Net COFUND programme, and with the funding organisations AEI, NWO, ECCyT and NSF Funding information, Allen-Perkins A, Magrach A, Dainese M, Garibaldi LA, Kleijn D, Rader R, Reilly JR, Winfree R, Lundin O, McGrady CM, Brittain C, Biddinger DJ, Artz DR, Elle E, Hoffman G, Ellis JD, Daniels J, Gibbs J, Campbell JW, Brokaw J, Wilson JK, Mason K, Ward KL, Gundersen KB, Bobiwash K, Gut L, Rowe LM, Boyle NK, Williams NM, Joshi NK, Rothwell N, Gillespie RL, Isaacs R, Fleischer SJ, Peterson SS, Rao S, Pitts-Singer TL, Fijen T, Boreux V, Rundlöf M, Viana BF, Klein AM, Smith HG, Bommarco R, Carvalheiro LG, Ricketts TH, Ghazoul J, Krishnan S, Benjamin FE, Loureiro J, Castro S, Raine NE, de Groot GA, Horgan FG, Hipólito J, Smagghe G, Meeus I, Eeraerts M, Potts SG, Kremen C, García D, Miñarro M, Crowder DW, Pisanty G, Mandelik Y, Vereecken NJ, Leclercq N, Weekers T, Lindstrom SAM, Stanley DA, Zaragoza-Trello C, Nicholson CC, Scheper J, Rad C, Marks EAN, Mota L, Danforth B, Park M, Bezerra ADM, Freitas BM, Mallinger RE, Oliveira da Silva F, Willcox B, Ramos DL, D da Silva E Silva F, Lázaro A, Alomar D, González-Estévez MA, Taki H, Cariveau DP, Garratt MPD, Nabaes Jodar DN, Stewart RIA, Ariza D, Pisman M, Lichtenberg EM, Schüepp C, Herzog F, Entling MH, Dupont YL, Michener CD, Daily GC, Ehrlich PR, Burns KLW, Vilà M, Robson A, Howlett B, Blechschmidt L, Jauker F, Schwarzbach F, Nesper M, Diekötter T, Wolters V, Castro H, Gaspar H, Nault BA, Badenhausser I, Petersen JD, Tscharntke T, Bretagnolle V, Willis Chan DS, Chacoff N, Andersson GKS, Jha S, Colville JF, Veldtman R, Coutinho J, Bianchi FJJA, Sutter L, Albrecht M, Jeanneret P, Zou Y, Averill AL, Saez A, Sciligo AR, Vergara CH, Bloom EH, Oeller E, Badano EI, Loeb GM, Grab H, Ekroos J, Gagic V, Cunningham SA, Åström J, Cavigliasso P, Trillo A, Classen A, Mauchline AL, Montero-Castaño A, Wilby A, Woodcock BA, Sidhu CS, Steffan-Dewenter I, Vogiatzakis IN, Herrera JM, Otieno M, Gikungu MW, Cusser SJ, Nauss T, Nilsson L, Knapp J, Ortega-Marcos JJ, González JA, Osborne JL, Blanche R, Shaw RF, Hevia V, Stout J, Arthur AD, Blochtein B, Szentgyorgyi H, Li J, Mayfield MM, Woyciechowski M, Nunes-Silva P, Halinski de Oliveira R, Henry S, Simmons BI, Dalsgaard B, Hansen K, Sritongchuay T, O'Reilly AD, Chamorro García FJ, Nates Parra G, Magalhães Pigozo C, Bartomeus I

1. Predicting plant–pollinator interaction networks over space and time will improve our understanding of how environmental change is likely to impact the functioning of ecosystems. Here we propose a framework for producing spatially explicit predictions of the occurrence and number of pairwise plant–pollinator interactions and of the species richness, diversity and abundance of pollinators visiting flowers. We call the framework ‘MetaComNet’ because it aims to link metacommunity dynamics to the assembly of ecological networks. 2. To illustrate the MetaComNet functionality, we used a dataset on bee–flower networks sampled at 16 sites in southeast Norway along with random forest models to predict bee–flower interactions. We included variables associated with climatic conditions (elevation) and habitat availability within a 250 m radius of each site. Regional commonness, site-specific distance to conspecifics, social guild and floral preference were included as bee traits. Each plant species was assigned a score reflecting its site-specific abundance, and four scores reflecting the bee species that the plant family is known to attract. We used leave-one-out cross-validations to assess the models' ability to predict pairwise plant–bee interactions across the landscape. 3. The relationship between observed occurrence or absence of interactions and the predicted probability of interactions was nearly proportional (GLMlogistic regression slope = 1.09), matching the data well (AUC = 0.88), and explained 30% of the variation. Predicted probability of interactions was also correlated with the number of observed pairwise interactions (r = 0.32). The sum of predicted probabilities of bee–flower interactions were positively correlated with observed species richness (r = 0.50), diversity (r = 0.48) and abundance (r = 0.42) of wild bees interacting with plant species within sites. 4. Our findings show that the MetaComNet framework can be a useful approach for making spatially explicit predictions and mapping plant–pollinator interactions. Such predictions have the potential to identify areas where the pollination potential for wild plants is particularly high, and where conservation action should be directed to preserve this ecosystem function. interactions, network, plants, pollinators, predict, random forest

Understanding interactions between individual animals and their resources is fundamental to ecology. Agent-Based Models (ABMs) offer an opportunity to study how individuals move given the spatial distribution and characteristics of their resources. When contrasted with empirical individual-resource network data, ABMs can be a powerful method to detect the processes behind observed movement patterns, as they allow for a complete and quantitative analysis of the agent-to-environment relationships. Here we use the small-scale, within-patch movement of bumblebees (Bombus pascuorum) as a case study to demonstrate how ABMs can be combined with network statistics to provide a deeper understanding of the mechanisms behind the interactions between individuals and their resources.We build an ABM that explicitly simulates the influence of distance to the nearest flowering plant (allowing minimal energy expenditure and maximum time spent foraging), plant height and number of flower heads (as a proxy of food availability) on local foraging decisions of bumblebees. The relative importance of these three elements is determined using pattern-oriented modelling (POM), where we confront the network statistics (number of visited plants, number of interactions, nestedness and modularity) of a real B. pascuorum individual-resource network with the emergent patterns of our ABM. We also explore the model results using spatial analysis.The model is able to reproduce the observed network statistics. Despite the complex behaviour of bumblebees, our results show a surprisingly precise match between the structure of the simulated and empirical networks after adjusting a single model parameter controlling the importance of distance to the next plant visited.Our study illustrates the potential of combining field data, ABMs and individual-resource networks for evaluating small-scale, within-patch movement decisions to better understand animal movements in natural habitats. We discuss the benefits of our approach when compared to more classical statistical methods, and its ability to test various scenarios in a new or altered environment. Understanding interactions between individual animals and their resources is fundamental to ecology. Agent-Based Models (ABMs) offer an opportunity to study how individuals move given the spatial distribution and characteristics of their resources. When contrasted with empirical individual-resource network data, ABMs can be a powerful method to detect the processes behind observed movement patterns, as they allow for a complete and quantitative analysis of the agent-to-environment relationships. Here we use the small-scale, within-patch movement of bumblebees (Bombus pascuorum) as a case study to demonstrate how ABMs can be combined with network statistics to provide a deeper understanding of the mechanisms behind the interactions between individuals and their resources. We build an ABM that explicitly simulates the influence of distance to the nearest flowering plant (allowing minimal energy expenditure and maximum time spent foraging), plant height and number of flower heads (as a proxy of food availability) on local foraging decisions of bumblebees. The relative importance of these three elements is determined using pattern-oriented modelling (POM), where we confront the network statistics (number of visited plants, number of interactions, nestedness and modularity) of a real B. pascuorum individual-resource network with the emergent patterns of our ABM. We also explore the model results using spatial analysis. The model is able to reproduce the observed network statistics. Despite the complex behaviour of bumblebees, our results show a surprisingly precise match between the structure of the simulated and empirical networks after adjusting a single model parameter controlling the importance of distance to the next plant visited. Our study illustrates the potential of combining field data, ABMs and individual-resource networks for evaluating small-scale, within-patch movement decisions to better understand animal movements in natural habitats. We discuss the benefits of our approach when compared to more classical statistical methods, and its ability to test various scenarios in a new or altered environment.

Recent studies have shown that sub-lethal doses of herbicides may affect plant flowering, however, no study has established a direct relationship between the concentrations of deposited herbicide and plant flowering. Here the aim was to investigate the relationship between herbicide spray drift deposited on non-target plants and plant flowering in a realistic agro-ecosystem setting. The concentrations of the herbicide glyphosate deposited on plants were estimated by measuring the concentration of a dye tracer applied together with the herbicide. The estimated maximal and average deposition of glyphosate within the experimental area corresponded to 30 g glyphosate/ha (2.08% of the label rate of 1440 g a.i./ha) and 2.4 g glyphosate/ha (0.15% label rate), respectively, and the concentrations decreased rapidly with increasing distance from the spraying track. However, there were not a unique relation between distance and deposition, which indicate that heterogeneities of turbulence, wind speed and/or direction can strongly influence the deposition from 1 min to another during spraying. The effects of glyphosate on cumulative flower numbers and flowering time were modelled using Gompertz growth models on four non-target species. Glyphosate had a significantly negative effect on the cumulative number of flowers on Trifolium pratense and Lotus corniculatus, whereas there were no significant effects on Trifolium repens, and a positive, but non-significant, effect on number of flowers on Cichorium intybus. Glyphosate did not affect the flowering time of any of the four species significantly. Lack of floral resources is known to be of major importance for pollinator declines. The implications of the presented results for pesticide risk assessment are discussed.

One of the socio-economically important West African parkland trees, Parkia biglobosa yields pods consumed by people and animals. Being animal-pollinated, it is unknown how climate change will affect the species if the guild of pollinators changes. Here, we compare the pollinator guilds and the pod production at two climatically different study sites: the first site, Tiba was drier with lower tree density and fewer fruit bats, whereas the second site, Pinyiri was more humid, with higher tree density and more fruit bats. We carried out a pollinator exclusion trial with bags separating the flower-visitors and made observations of the flower-visitors. Furthermore, we calculated pollination distances based on paternity analysis of the seeds produced within the trial. The numbers of immature fruits were similar for the sites, but the drier site, Tiba experienced more abortion and decreased pod set. At both sites, exclusion of bats led to marginally reduced pod set, while exclusion of bats and honey bees led to significantly reduced pod set. We found a small effect of stingless bees and solitary bees but only at the more humid site, Pinyiri. Tiba experienced a higher level of self-pollination, fewer pollen donors per tree, and longer median distances of pollen flow, compared with Pinyiri. Implications of the results for management of the species and its pollinators in the face of climate change are discussed.

Shea (Vitellaria paradoxa) is an important fruit tree in West African parklands, and itssuccessful pollination is a requirement for fruit production. Size-based pollinatorexclusion experiments combined with visual observations showed that presence ofhoney bees (Apis mellifera jemenitica) was important for pollination and thereby theproduction of fruits and seeds. Smaller insects, mainly species of stingless bees(Hypotrigona spp. and Liotrigona cf. bottegoi) and solitary bees (Compsomelissaborneri) could partly compensate pollination in absence of honey bees, but fertilisationand fruit yield was reduced. A positive correlation between fertilisation percentage andnumber of honey bee colonies within radii of 900 m and 1,000 m was observed. Thepercentage of fertilisation and number of mature fruits per fascicle were higher in treeswith colonies of stingless bees in the trunk when honey bees were excluded bybagging. We conclude that local beekeeping with honey bees and stingless bees islikely to have a positive influence on fruit production of shea trees in the farmed WestAfrican parklands, which speaks in favour of a pollinator friendly environment.

In their Perspective “Conserving honey bees does not help wildlife” (26 January, p. [392][1]), J. Geldmann and J. P. Gonzalez-Varo point out that promoting managed honey bees does not help wild pollinators. We agree that, at high densities, honey bees can adversely affect wild pollinator

Herbicides and nitrogen fertilizers are widely used in intensively grown agricultural areas. Non-target plants growing in habitats adjacent to conventional fields may be exposed to herbicides by spray drift and misplacement of nitrogen fertilizers. Whereas sub-lethal effects of herbicides have previously been documented, combined effects of nitrogen and sub-lethal herbicide exposure are less well known. Moreover, indirect effects on pollination and fruit set following effects of agrochemicals on flowering remain largely unexplored. In the current study, we investigate combined effects of herbicide and nitrogen fertilizer on reproductive features of Tanacetum vulgare (Asteraceae). The study was carried out in an experimental set-up, in which plots of 7 × 7 m were treated with one of six treatments: four levels of the herbicide glyphosate (0%, 1%, 5%, and 25% of label rate of 1440 g a.i. ha−1) without nitrogen in addition to two levels of herbicide (0% and 25%) with added nitrogen (100 kg N ha−1 year−1). The set-up had a randomized full-factorial design with 10 replicates of each treatment. We monitored floral density per plot every fortnight during flowering, stem height at flowering, diameter of capitula, visitation rate and diversity of flower-visitors, in addition to weight per seed and total seed weight per seed head. Glyphosate, nitrogen and their interaction affected plant reproductive features, in particular, floral density and flowering phenology. Glyphosate negatively affected floral density, and flowering was severely delayed by glyphosate application (10.5 days delay per 100 g a.i. ha−1 year−1). Although nitrogen partly mitigated reduction in floral abundance, the delay in flowering was amplified when nitrogen was added. Effects of glyphosate on flowering were mirrored in reduced flower visitation by insects and reduced seed set. These effects occurred even when plants were exposed to glyphosate two months before onset of flowering. Our results show that misplacement of agro-chemicals markedly changes floral abundance and flowering phenology of non-target plants, which may secondarily impact pollination interactions and reproduction of wild plants in agricultural landscapes.

Theinfluence of space on the structure (e.g. modularity) of complex ecological networks remains largely unknown. Here, wesampled an individual-based plant–pollinator network by following the movements and flower visits of marked bumblebeeindividuals within a population of thistle plants for which the identities and spatial locations of stems were mapped in a50  50 m study plot. The plant–pollinator network was dominated by parasitic male bumblebees and had a significantlymodular structure, with four identified modules being clearly separated in space. This indicated that individual flowervisitors opted for the fine-scale division of resources, even within a local site. However, spatial mapping of network modulesand movements of bumblebee individuals also showed an overlap in the dense center of the plant patch. Model selectionbased on Akaike information criterion with traits as predictor variables revealed that thistle stems with high numbersof flower heads and many close neighbours were particularly important for connecting individuals within the modules.In contrast, tall plants and those near the patch center were crucial for connecting the different modules to each other.This demonstrated that individual-based plant–pollinator networks are influenced by both the spatial structure of plantpopulations and individual-specific plant traits. Additionally, bumblebee individuals with long observation times wereimportant for both the connectivity between and within modules. The latter suggests that bumblebee individuals will stillshow locally restricted movements within sub-patches of plant populations even if they are observed over a prolonged timeperiod. Our individual-based and animal-centered approach of sampling ecological networks opens up new avenues forincorporating foraging behaviour and intra-specific trait variation into analyses of plant–animal interactions across space.

International audience; Red clover is a key floral ressource for bumblebees (Bombus spp.). We here investigate variation within and among red clover fields in species richness and abundance of Bombus spp. in addition to Apis mellifera. Bumblebee individuals were grouped into the following functional groups, based on castes and tongue length: (1) all queens, (2) all workers, (3) short-tongued workers and (4) long-tongued workers. In 14 study fields, no spatial or diurnal within-field differences were found in abundances of bee groups. However, seasonal differences were detected. On average 6.3 ± 0.6Bombus spp. were observed in each field. In general, maximum observed bee abundances of a field were not associated with field size, weediness, or presence of commercial honeybee hives. However, long-tongued bumblebee abundance was significantly lower in fields with beehives. Seed yield was marginally higher in less weedy fields, but not significantly augmented by presence of bee hives.

The introduction of an alien top predator, the brown treesnake (Boiga irregularis), has resulted in severe losses of native vertebrate populations in Guam. Among these are important pollinators and seed dispersers. This study is a first attempt to document cascading effects on vertebrate-pollinated native plant species in Guam. We investigated flower visitation, seed set and germination in two native plants, the mangrove tree Bruguiera gymnorrhiza and the forest tree Erythrina variegata var. orientalis. Both species are bird-pollinated. Studies were conducted on two Mariana islands, Guam (with high density of snakes) and Saipan (with nearly no snakes). Visitation rates by birds were high on Saipan, but zero on Guam. Insects and lizards visited flowers to a low extent on both islands. Only lizards were potential effective pollinators. Seed set of both species were significantly higher on Saipan compared to Guam, and for B. gymnorrhiza, seedling recruitment was significantly higher on Saipan. Hence, these bird-pollinated species appear highly dependent on bird visitors for reproduction. The eradication of flower-visiting birds by the invasive treesnake thus secondarily results in broken mutualistic interactions, which may, in turn, result in a lower recruitment of native plants. Thus, the treesnake affects not only potential prey species, but its effects cascade through the entire ecosystem on Guam. Conservation actions should be directed towards an improved recruitment (artificial pollination, planting) of the affected plant species.

In natural communities, species and their interactions are often organized as nonrandom networks, showing distinct and repeated complex patterns. A prevalent, but poorly explored pattern is ecological modularity, with weakly interlinked subsets of species (modules), which, however, internally consist of strongly con- nected species. The importance of modularity has been discussed for a long time, but no consensus on its prevalence in ecological networks has yet been reached. Progress is hampered by inade- quate methods and a lack of large datasets. We analyzed 51 pollination networks including almost 10,000 species and 20,000 links and tested for modularity by using a recently developed simulated annealing algorithm. All networks with >150 plant and pollinator species were modular, whereas networks with

Heathlands of Northwest Europe, which once covered extensive areas, are now reduced to small and large fragments in an agricultural landscape. In this study, we investigate the effect of fragmentation on the flower-visiting insect fauna in relation to species composition, level of specialization/generalization at the adult and larval stages, and larval trophic level. Two study sites were used: a large continuous tract of heathland, and a fragmented mosaic area. The assemblages of entomophilous plants at the two sites were similar. However, of a total of 256 species of flower-visiting insects observed, only 108 were shared between the two sites. The fragmented heath supported a taxonomically and ecologically more diverse assemblage of flower-visitors, compared to the extensive heath. At both sites, the majority of adult flower-visiting insect species were generalists, consuming floral resources from a variety of flowers. Larval types encompassed both specialists and generalists, represented by a spectrum of trophic groups, feeding classes and substrates. Species presence was dependent on the availability of larval resources and habitats rather than the requirements of imagines. No difference in level of specialization of adults or larvae was found between sites. Fragmentation affected trophic-level structure among larval specialists, significantly more high trophic-level species being found at the continuous heath tract, compared to the fragmented area. In contrast, no effect was observed among larval generalists, supporting the trophic-level hypothesis of island biogeography. Thus, although species richness is not negatively affected, composition and trophic structure is markedly changed by fragmentation of heathlands.

Summary 1The bird-flower element of the Canary Islands is a group of endemic plants having traits characteristic of bird pollination, and some are visited by opportunistically nectar-feeding passerine birds. 2We investigated evolutionary changes in nectar sugar composition in seven Canarian lineages of ornithophilous plant species and their entomophilous relatives. 3We hypothesized that nectar sugar composition evolved in response to the main pollinator group of a plant. Specialist nectarivores can assimilate sucrose, whereas some opportunistic nectar-feeders digest only the simple hexoses. 4Sugar composition of nectars was analysed using high pH anion exchange chromatography. 5Evolution of nectar type was correlated with mode of pollination. Generally, sucrose nectars were associated with insect visitation and hexose nectars with bird visitation. Nectar sugar composition was an evolutionary labile trait within a lineage. Hence, nectar characteristics may have evolved readily, perhaps in response to opportunistically nectarivorous birds living in the Canary Islands.

The aim of this study was to investigate effects of introduced honey bees (Apis mellifera) on native pollination interactions of Echium wildpretii ssp. wildpretii in the sub-alpine desert of Tenerife. We selected two study populations, one dominated by honey bees, while the other was visited by many native insects. During peak activity period of insects, nectar was nearly completely depleted in flowers of the first, but not the latter population. Thus, a high abundance of honey bees may have suppressed visitation by native animals due to exploitative competition. Honey bees stayed longer and visited more flowers on the same inflorescence than native bees, thus potentially promoting self-pollination of the plants. Level of seed set and viability was similar in the two study populations. However, we cannot rule out long-term changes in genetic population structure due to changes in gene-flow patterns caused by foraging behaviour of honey bees vs. native flower-visitors.

Echium (Boraginaceae) is one of the largest evolutionary radiations in the Canary Islands and exhibits considerable variation in geographical distribution patterns and floral characters. Flower visitors are mainly bees (Hymenoptera: Apoidea). We investigated factors determining the level of generalization for pollination in 20 endemic and one introduced species of Echium in the archipelago. For each Echium species, we analyzed variation in species richness of bee visitors in relation to geographical distribution of the plants (area and altitude), floral traits (morphology and color), and sampling effort (observation time and number of study populations). Geographical distribution range was the only good predictor of species richness of bees. In our study, widespread species of Echium were visited by a larger fraction of Echium‐visiting bee taxa than were rare species. Thus, plant commonness per se may act as a strong attractant of bees. Alternatively, if widespread species interact with different flower v...

Confined within a volcanic caldera at 2000 m a.s.l., the sub-alpine desert of Tenerife, Canary Islands, harbors a distinct biota. At this altitude the climate is harsh and the growing season short. Hence, plant and animal communities, constituting the sub-alpine plant-flower-visitor network, are clearly delimited, both spatially and temporally. We investigated species composition and interaction structure of this system. A total of 11 plant species (91% endemics) and 37 flower-visiting animal species (62% endemics) formed 108 interactions. Numbers of interactions among species varied ten-fold within both plant and animal communities. Generalization level of a species was positively correlated with its local abundance. Two separate network analyses revealed a significantly nested structure. In relation to a plant-flower-visitor system, nestedness implies that specialized species (animals or plants) interact with a subset of the species pool visiting (animals) or being visited (plants) by more generalized species. Therefore, specialized, locally rare plants tend to be visited by generalized, locally abundant animals, and specialized, locally rare animals tend to utilize generalized, locally abundant food plants. Such patterns could have implications for conservation of the sub-alpine network, and stress the importance of preserving not only rare species, but also the more abundant ones, which may be key food resources or pollinators in the plant-flower-visitor network.

In this paper, we report observations of flower visitors of the endemic Echium wildpretii in Tenerife, Canary Islands. This plant inhabits the high altitudinal sub-alpine zone, which is characterized by a harsh climate, low species diversity and a short growing season. Echium wildpretii is a monocarpic perennial, producing a 2–3 m column-shaped, red-flowered, nectar-rich inflorescence. Although these floral traits have previously been suggested as being typical of ornithophilous flowers, this is the first study reporting observations of native birds (Phylloscopus collybita and Serinus canarius) in addition to insects visiting the flowers for nectar. The purposes of this study were firstly to investigate levels of visitation by native birds, native insects, and introduced honey bees. Secondly, we studied the influence of floral display (plant height and number of flowers), nearest neighbours (distance and size) and local vegetation structure on visitation rate. Finally, we discuss the evolution of ornithophily in an otherwise entomophilous plant lineage. We found that the level of bird visitation was relatively high early in the flowering season, but decreased in mid/late season, while the opposite pattern was found for introduced honey bees. For native insects, the frequency of visits was similar in early and late season. Bird visits were correlated with floral display. In the early season, visitation rates of honey bees and the two most common native bee species were correlated with size of the plant or its nearest neighbours, consistent with preference patterns for larger resource patches. Since only insects visit the flowers of other species in the Echium clade, E. wildpretii appears to have evolved from a truly insect-pollinated lineage.

I have investigated the reproductive biology of four dioecious species of Lindera in Japan: Lindera obtusiloba Bl., L. umbellata Thunb., L. erythrocarpa Makino, and L. glauca Bl. The sex ratios in populations of the first three species are close to equality, but in L. glauca only female individuals are found in Japan, although males are known from continental Asia. The persistence of this dioecious species in the absence of males is surprising, and prompts the question: What mechanisms operate to ameliorate problems of colonization in species of Lindera? I carried out bagging experiments in order to test for apomixis (asexual reproduction by seeds) and to establish the importance of pollination and fertilization, and potential pollen vectors. Only L. glauca reproduced by apomixis. Level of fruit set was high, and was not affected by pollination. In the other three species, seed set was entirely dependent on pollen transfer, which could be accomplished by small Coleoptera and Diptera. The evolution of apomixis in L. glauca appears to have been a strategy to overcome sterility and establish a population in the Japanese islands even in the absence of males. However, this change in breeding system has not occurred in congeneric, co-occurring species, which do not seem to have experienced a lack of male plants.

In this study we investigated floral biology and flower-visiting insect fauna in natural populations of six dioecious species of Lindera (Lauraceae) in Kyoto, Japan. Flowers of the Lindera species were similar in structure and floral attractants, and were visited by a wide range of insects. Although typical of generalist-pollinated flowers, interspecific differences were found in flower-visitor composition. All species of Lindera flowered early in the growing season, from February to May. However, peak flowering periods of different species of Lindera were staggered. Slight interspecific and intersexual divergence of flowering phenologies may reduce interspecific cross-pollination. Results of this study suggest that interspecific segregation of pollinators was associated with seasonal divergence of phenological patterns, rather than character displacement of floral attractants.

Adult body mass is a strong correlate of many important life history traits of bees, and thus, has been used as a proxy for these traits in ecological studies. However, body mass is difficult to measure on live specimens in the field, and impossible to measure non-destructively on dry museum specimens. For worker and male bumblebees, we evaluated the linear measures inter-tegular span (IT span) and head width as predictors of fresh and dry weight. For males, linear regressions best explained the relationship between fresh and dry weight and the linear size estimators, while for workers, exponential regressions best explained this relationship. We found that both IT span and head width are precise estimators of weights of bumblebees. Head width was a slightly better predictor of male weights, while IT span was a slightly better predictor of worker weights. IT span and head width changed little by drying. We discuss patterns of size variation in bumblebees, and highlight possible applications of the method in ecological studies.

Modularity is a structural property of ecological networks, which has received much interest, but has been poorly explored. Modules are distinct subsets of species interacting strongly with each other, but sparsely with species outside the subset. Using a series of temporal cumulative networks, we investigated the stability of modular organization of pollination networks to temporal scaling. To test for modularity, we used the method ‘functional cartography by simulated annealing’ ( Guimera and Amaral, 2005a , Guimera and Amaral, 2005b ), a stochastic optimization technique. Modules are detected, and species classified into three types of topological roles in a network, based on patterns of within and between-module links: Hubs are highly connected species; peripherals interact with few species, mainly within their own module; and connectors have few interactions, too, but link across modules. We observed interactions between all flowering plants and flower-visiting insect species throughout the flowering season at three dry heathland sites in Denmark. For each site, we constructed cumulative networks every 0.5 months, resulting in series of 10–12 networks per site. Numbers of interactions, and plant and insect species accumulated throughout the period, while level of modularity (M) and number of modules (NM) was largely invariant to temporal scaling. The proportions of hub, peripheral and connector species were unaffected by scaling of the network. The networks had a multi-star structure, consisting of modules each formed around one or two hubs. These hub species encompassed a small number of plant species, many of which acted as hubs at several study sites and throughout most of their flowering season. Thus, these plants become of key importance in maintaining the structure of their pollination network. We conclude that the modular structure of heathland pollination networks is stable to temporal scaling, a pattern repeatedly found at three sites of similar habitat.

A longstanding hypothesis (“Baker's rule”) is that plant invasiveness is facilitated by floral self compatibility rather than self incompatibility. Extending this idea, invasive species whose individuals vary in degree of self compatibility within the native range might be self compatible in invading or weedy populations, due to natural selection on the mating system. We compared mating system between native and invasive ranges for two major world invasives, one annual (Echium plantagineum) and one perennial (Solanum elaeagnifolium). For an additional annual species (Centaurea solstitialis) we compared non-weedy and weedy populations in the native range. No species was strongly spontaneously self pollinating, but the degree of self compatibility after hand pollination varied dramatically. Both annuals were self incompatible in native or non-weedy populations but self compatible in invasive or weedy ones; the reverse was true for the perennial. Individuals within populations of all three species also varied in their degree of self compatibility, suggesting a basis for natural selection, and populations of the same species sharing a status (native/non-weedy, invading/weedy) varied in average self compatibility. These results support the hypothesis that differential selection of progeny during invasion can result in self-compatible populations derived from ancestrally self-incompatible ones, but that this process may be less important in perennial species, which experience multiple opportunities for sexual reproduction. Overall, however, mating system may not operate alone and its contributions to invasiveness may be conditional on other attributes of a species including physiology, morphology, and life history.

Ecological networks are complexes of interacting species, but not all potential links among species are rea- lized. Unobserved links are either missing or forbidden. Missing links exist, but require more sampling or alternative ways of detection to be verified. Forbidden links remain unobservable, irrespective of sampling effort. They are caused by linkage constraints. We studied one Arctic pollination network and two Mediter- ranean seed-dispersal networks. In the first, for example, we recorded flower-visit links for one full season, arranged data in an interaction matrix and got a connectance C of 15 per cent. Interaction accumulation curves documented our sampling of interactions through observation of visits to be robust. Then, we included data on pollen from the body surface of flower visitors as an additional link ‘currency’. This resulted in 98 new links, missing from the visitation data. Thus, the combined visit – pollen matrix got an increased C of 20 per cent. For the three networks, C ranged from 20 to 52 per cent, and thus the percen- tage of unobserved links (100 2 C ) was 48 to 80 per cent; these were assumed forbidden because of linkage constraints and not missing because of under-sampling. Phenological uncoupling (i.e. non-overlapping phe- nophases between interacting mutualists) is one kind of constraint, and it explained 22 to 28 per cent of all possible, but unobserved links. Increasing phenophase overlap between species increased link probability, but extensive overlaps were required to achieve a high probability. Other kinds of constraint, such as size mismatch and accessibility limitations, are briefly addressed.

Studies of ecological networks usually focus upon interaction patterns among species. However, linkage among species is mediated by their constituting individuals. Thus, every linked species pair in a network encapsulates a new network of interacting individuals. Very few studies outside the sociology of larger animals have investigated networks at the level of the individual. Here, we analyse the structure of a flower–visitation network of individual thistles Cirsium arvense and honeybees Apis mellifera in a small meadow patch in Denmark. We marked and numbered 62 honeybees and 32 thistle stems and monitored all floral visits. The constructed bipartite network of individual plants and bees had a high connectance and low nestedness, but it was not significantly modular. Frequency distributions of number of links per species (i.e. linkage level) had their best fit to a truncated power law, and interactions were asymmetrical. Unipartite networks of either plants or bees had exceedingly short average path length and high clustering. Linkage level of plants increased with their number of flower heads and height of inflorescence (floral display parameters). Overall, the individual network of honeybees and thistles was denser linked than what is known from species pollination networks. Characteristics of both plants (e.g. floral display) and animals (e.g. foraging behaviour) are likely to generate this intra–specific, inter–individual link pattern. Such features of individual–individual networks may scale up and become important drivers of the structure and dynamics of species–species networks.

Ecological networks are typically complex constructions of species and their interactions. During the last decade, the study of networks has moved from static to dynamic analyses, and has attained a deeper insight into their internal structure, heterogeneity, and temporal and spatial resolution. Here, we review, discuss and suggest research lines in the study of the spatio-temporal heterogeneity of networks and their hierarchical nature. We use case study data from two well-characterized model systems (the food web in Broadstone Stream in England and the pollination network at Zackenberg in Greenland), which are complemented with additional information from other studies. We focus upon eight topics: temporal dynamic space-for-time substitutions linkage constraints habitat borders network modularity individual-based networks invasions of networks and super networks that integrate different network types. Few studies have explicitly examined temporal change in networks, and we present examples that span from daily to decadal change: a common pattern that we see is a stable core surrounded by a group of dynamic, peripheral species, which, in pollinator networks enter the web via preferential linkage to the most generalist species. To some extent, temporal and spatial scales are interchangeable (i.e. networks exhibit ‘ergodicity’) and we explore how space-for-time substitutions can be used in the study of networks. Network structure is commonly constrained by phenological uncoupling (a temporal phenomenon), abundance, body size and population structure. Some potential links are never observed, that is they are ‘forbidden’ (fully constrained) or ‘missing’ (a sampling effect), and their absence can be just as ecologically significant as their presence. Spatial habitat borders can add heterogeneity to network structure, but their importance has rarely been studied: we explore how habitat generalization can be related to other resource dimensions. Many networks are hierarchically structured, with modules forming the basic building blocks, which can result in self-similarity. Scaling down from networks of species reveals another, finer-grained level of individual-based organization, the ecological consequences of which have yet to be fully explored. The few studies of individual-based ecological networks that are available suggest the potential for large intraspecific variance and, in the case of food webs, strong size-structuring. However, such data are still scarce and more studies are required to link individual-level and species-level networks. Invasions by alien species can be tracked by following the topological ‘career’ of the invader as it establishes itself within a network, with potentially important implications for conservation biology. Finally, by scaling up to a higher level of organization, it is possible to combine different network types (e.g. food webs and mutualistic networks) to form super networks, and this new approach has yet to be integrated into mainstream ecological research. We conclude by listing a set of research topics that we see as emerging candidates for ecological network studies in the near future.

1. Co-existing plants and flower-visiting animals often form complex interaction networks. A long-standing question in ecology and evolutionary biology is how to detect nonrandom subsets (compartments, blocks, modules) of strongly interacting species within such networks. Here we use a network analytical approach to (i) detect modularity in pollination networks, (ii) investigate species composition of modules, and (iii) assess the stability of modules across sites.2. Interactions between entomophilous plants and their flower-visitors were recorded throughout the flowering season at three heathland sites in Denmark, separated by ≥ 10 km. Among sites, plant communities were similar, but composition of flower-visiting insect faunas differed. Visitation frequencies of visitor species were recorded as a measure of insect abundance.3. Qualitative (presence-absence) interaction networks were tested for modularity. Modules were identified, and species classified into topological roles (peripherals, connectors, or hubs) using 'functional cartography by simulated annealing', a method recently developed by Guimerà & Amaral (2005a).4. All networks were significantly modular. Each module consisted of 1-6 plant species and 18-54 insect species. Interactions aggregated around one or two hub plant species, which were largely identical at the three study sites.5. Insect species were categorized in taxonomic groups, mostly at the level of orders. When weighted by visitation frequency, each module was dominated by one or few insect groups. This pattern was consistent across sites.6. Our study adds support to the conclusion that certain plant species and flower-visitor groups are nonrandomly and repeatedly associated. Within a network, these strongly interacting subgroups of species may exert reciprocal selection pressures on each other. Thus, modules may be candidates for the long-sought key units of co-evolution.

Using a sample of 1,403 flowering plant species, we tested the hypothesis that flower openness and flower-visitor aeneralization level of a plant species correlate positively. The "flower-visitor generalization level" L. of a flo, vering plant species n, here defined as number of flower-visiting animal species attracted to the flowers of n in a aiven study site, varied enormously among plant species. Its frequency distribution was extremely skewed. Within a study site, L also increased with number of flower-visitor species A. In order to correct for this, ve expressed L relatively, as the proportion of the total flower-visitor fauna in a study site that visited a gyiv-en plant species (relative generalization level, L/A). We listed the top-10 most generalized species (both according to L and LIA) in the "world", i.e., out of our sample of 1,403 plant species. Flower openness is defined as accessibilitv to the interior of the flower. We placed the blossom classes of Facgri & van der Pijl along a aradient, albeit not very well defined, of decreasing flower openness (dish-bowl, bell-funnel, head-brush, tube. aullet. flag) and tested for any relationship to their generalization level. The classes differed slightly but significantly in their level of L/A. Tube, bell-funnel, and dish-bowl had the highest generalization level and flaLy. uullet. and head-brush the lowest. Thus, flower openness and generalization level were not correlated. We discuss other factors influencing generalization level such as accessibility to pollen and nectar, morphology and behavior of visitor, and species diversity of the different functional types of visitors.

We investigated the pollination and reproductive biology of two Canary Island endemics, Solanum vespertilio and S. lidii (Solanaceae). We measured male function (pollen development), female function (fruit initiation) and spatial arrangement of reproductive parts within flowers and inflorescences. Furthermore, we observed flower visitors and monitored visitation rates. Both species of Solanum display andromonoecy: Longstyled flowers are functionally hermaphrodite and borne proximally on the inflorescences, while short-styled flowers are functionally male and borne distally on inflorescences. Large bees capable of buzzing were the main flower visitors. In particular, the endemic Canarian bumblebee, Bombus terrestris canariensis, was a frequent visitor and pollen vector of S. vespertilio.

A pollination network may be either 2-mode, describing trophic and reproductive interactions between communities of flowering plants and pollinator species within a well-defined habitat, or 1-mode, describing interactions between either plants or pollinators. In a 1- mode pollinator network, two pollinator species are linked to each other if they both visit the same plant species, and vice versa for plants. Properties of 2-mode networks and their derived 1-mode networks are highly correlated and so are properties of 1-mode pollinator and 1-mode plant networks. Most network properties are scale-dependent, i.e. they are dependent upon network size. Pollination networks have the strongest small-world properties of any networks yet studied, i.e. all species are close to each other (short average path length) and species are highly clustered. Species in pollination networks are much more densely linked than species in traditional food webs, i.e. they have a higher density of links, a shorter distance between species, and species are more clustered.

Jasminum odoratissimum is a Madeira and Canary Islands endemic showing classic heterostyly, i.e. with long-styled flowers with anthers at a low level in the corolla tube and short-styled flowers with anthers at a high level in the corolla tube. Short-styled flowers have large pollen whereas long-styled flowers have small pollen. The two types are present in equal frequencies in the population.

Aims: Several bird-pollinated or ornithophilous flowers are present on the Macaronesian archipelagos, the Canary Islands and Madeira, but absent from nearby NW Africa and Europe. In Macaronesia, no specialist nectar-feeding birds are found, but several generalist passerine bird species visit flowers for nectar. Two hypotheses attempt to explain the origin and evolution of ornithophily in the Macaronesian flora. According to 'the island de novo hypothesis', bird-flowers evolved from mainland insect-pollinated ancestors after island colonization. Alternatively, ancestors of the ornithophilous Macaronesian plant species evolved bird-flowers before reaching the islands ('the relict hypothesis'). In this study we first compile information of Macaronesian bird-flower interactions from the literature and our own field observations. Secondly, we discuss the two hypotheses of origin of ornithophily in the light of evidence from recent molecular plant phylogenies, palaeontology, historical biogeography of the African avifauna and flora, and present-day ecological patterns. Location: Madeira and Canary Islands. Results: At least eleven endemic Macaronesian plant species from six genera have typical ornithophilous floral traits. These genera are: Canarina and Musschia (Campanulaceae), Isoplexis (Scrophulariaceae), Echium (Boraginaceae), Lotus (Fabaceae) and Lavatera (Malvaceae). These lineages have clear affinities to the Mediterranean region, except for Canarina whose closest relatives grow in East African mountains. Six generalist passerine bird species of Sylvia, Phylloscopus (Sylviidae), Serinus (Fringillidae) and Parus (Paridae) visit this flora for nectar. Main conclusion: We suggest that the origin and evolution of ornithophilous traits in these plant species took place mostly in mainland areas prior to island colonization. In Canarina and Lavatera, it is well supported that ornithophily is a relict condition, which originated in mainland areas possibly in association with specialist nectar-feeding birds. For the remaining plant species except Echium wildpretii bird floral traits probably also are a relict condition. These species may be derived from ancestors, which were visited by specialist nectar-feeding birds during geological periods when the Mediterranean and the Ethiopian vegetation were intermingled in mainland Africa. Probably, these mainland ancestors went extinct due to severe climatic fluctuations, while their Macaronesian descendants survived in 'refuge' on the islands. Finally, the island de novo hypothesis may explain the evolution of a mixed bird/insect-pollination system in the neoendemic red-flowered Echium wildpretii.

Dupont Yoko L., Hansen Dennis, Valido Alfredo, Olesen Jens M. Introduced honeybees on islands: impacts on native pollination interactions. In: Ecologia mediterranea, tome 30 n°2, 2004. pp. 236-237.