Last Document Library from step-project.net http://www.step-project.net Mon, 04 May 2026 16:53:27 +0200 WebDesign LTD. FeedCreator http://www.step-project.net/files/DOWNLOAD/40032_LI_long distance dispersal_Byasa impediens.pdf 10 March 2015

Long-distance dispersal and habitat use of the butterfly Byasa impediens in a fragmented subtropical forest

1. Central and Southeast Asia currently faces rapid loss and degradation of tropical and subtropical forests with potentially severe effects on its biodiversity. 2. We analysed population characteristics and dispersal of the butterfly Byasa impediens in eleven patches of a fragmented subtropical forest in Western China. 3. In an area covering 30 km2, we found an unexpected high dispersal capacity of more than 5 km, and estimated a mean dispersal distance of 1 km according to the negative exponential function. However, the inverse power function gave a better fit and predicted a reasonably large fraction of long-distance displacements: 4% of all movements were estimated to exceed 5 km. 4. In spite of the high level of fragmentation and small sizes of some patches, we did not observe extinction or (re)colonisation events. Matching dispersal ability with the spatial grain of the resource patches in the landscape is seen as a major cause. In addition, persistence, emigration and immigration of individuals were exclusively affected by the amount of larval host plants, nectar plants and forest cover. 5. Our study indicates the importance of long-distance dispersal and shows that species with large dispersal abilities and a somewhat broader dietary niche, such as B. impediens, can sustain in fragmented areas if patch quality is sufficient. 6. We suggest that conservation action may not only focus on particularly endangered species but also on relatively common, but often endemic, insect species. This is of particular concern given the global dominance of insects and their importance for ecosystem services, especially in an area of constantly increasing demands of agricultural products.

]]> Tue, 10 Mar 2015 11:00:00 +0200 http://www.step-project.net/files/DOWNLOAD/2013 Garibaldi et al. Science.pdf 10 March 2015

Wild Pollinators Enhance Fruit Set of Crops Regardless of Honey Bee Abundance

The diversity and abundance of wild insect pollinators have declined in many agricultural landscapes. Whether such declines reduce crop yields, or are mitigated by managed pollinators such as honey bees, is unclear. We found universally positive associations of fruit set with flower visitation by wild insects in 41 crop systems worldwide. In contrast, fruit set increased significantly with flower visitation by honey bees in only 14% of the systems surveyed. Overall, wild insects pollinated crops more effectively; an increase in wild insect visitation enhanced fruit set by twice as much as an equivalent increase in honey bee visitation. Visitation by wild insects and honey bees promoted fruit set independently, so pollination by managed honey bees supplemented, rather than substituted for, pollination by wild insects. Our results suggest that new practices for integrated management of both honey bees and diverse wild insect assemblages will enhance global crop yields.

]]> Tue, 10 Mar 2015 11:00:00 +0200 http://www.step-project.net/files/DOWNLOAD/2014 Garibaldi et al. Frontiers.pdf 10 March 2015

From research to action: enhancing crop yield through wild pollinators Read More: http://www.esajournals.org/doi/abs/10.1890/130330

Recent evidence highlights the value of wild-insect species richness and abundance for crop pollination worldwide. Yet, deliberate physical importation of single species (eg European honey bees) into crop fields for pollination remains the mainstream management approach, and implementation of practices to enhance crop yield (production per area) through wild insects is only just beginning. With few exceptions, studies measuring the impacts of pollinator-supporting practices on wild-insect richness and pollination service success – particularly in relation to long-term crop yield and economic profit – are rare. Here, we provide a general framework and examples of approaches for enhancing pollinator richness and abundance, quantity and quality of pollen on stigmas, crop yield, and farmers\' profit, including some benefits detected only through long-term monitoring. We argue for integrating the promotion of wild-insect species richness with single-species management to benefit farmers and society

]]> Tue, 10 Mar 2015 11:00:00 +0200 http://www.step-project.net/files/DOWNLOAD/2014_CloughEkroosetal-ELE-earlyview.pdf 10 March 2015

Density of insect-pollinated grassland plants decreases with increasing surrounding land-use intensity

Pollinator declines have raised concerns about the persistence of plant species that depend on insect pollination, in particular by bees, for their reproduction. The impact of pollinator declines remains unknown for species-rich plant communities found in temperate seminatural grasslands. We investigated effects of land-use intensity in the surrounding landscape on the distribution of plant traits related to insect pollination in 239 European seminatural grasslands. Increasing arable land use in the surrounding landscape consistently reduced the density of plants depending on bee and insect pollination. Similarly, the relative abundance of bee-pollination-dependent plants increased with higher proportions of non-arable agricultural land (e.g. permanent grassland). This was paralleled by an overall increase in bee abundance and diversity. By isolating the impact of the surrounding landscape from effects of local habitat quality, we show for the first time that grassland plants dependent on insect pollination are particularly susceptible to increasing land-use intensity in the landscape.

]]> Tue, 10 Mar 2015 11:00:00 +0200 http://www.step-project.net/files/DOWNLOAD/2012 Api Maebe B. veteranus.pdf 10 March 2015

Microsatellite analysis in museum samples reveals inbreeding before the regression of Bombus veteranus

The worldwide decline of pollinators is an emerging threat and is a matter both for ecological and economic concerns. Population genetics can be used to correlate bumblebee decline with genetic parameters. In order to do so, historical data are needed. We used eight microsatellite loci to genotype pinned museum specimens of the declining bumblebee Bombus veteranus. Bumblebee samples were collected spanning a period of three decades (1895–1923). We detected low genetic diversity and inbreeding in the samples collected during the respective time periods. Inbreeding was also confirmed by the occurrence of sterile diploid males. Based on the data obtained, we speculate that low genetic diversity and inbreeding did not directly result in the collapse of B. veteranus in Belgium. However, inbreeding might still play an indirect role in the decline of bumblebee populations because of the appearance of diploid males and because a low H E might reduce the capacity to react to the drivers of bumblebee decline.

]]> Tue, 10 Mar 2015 11:00:00 +0200 http://www.step-project.net/files/DOWNLOAD/2011_Nielsenetal_Ecol-Res.pdf 10 March 2015

Assessing bee species richness in two Mediterranean communities: importance of habitat type and sampling techniques

The decline of bees has raised concerns regarding their conservation and the maintenance of ecosystem services they provide to bee-pollinated wild flowers and crops. Although the Mediterranean region is a hotspot for bee species richness, their status remains poorly studied. There is an urgent need for cost-effective, reliable, and unbiased sampling methods that give good bee species richness estimates. This study aims: (a) to assess bee species richness in two common Mediterranean habitat types: semi-natural scrub (phrygana) and managed olive groves; (b) to compare species richness in those systems to that of other biogeographic regions, and (c) to assess whether six different sampling methods (pan traps, variable and standardized transect walks, observation plots and trap nests), previously tested in other European biogeographic regions, are suitable in Mediterranean communities. Eight study sites, four per habitat type, were selected on the island of Lesvos, Greece. The species richness observed was high compared to other habitat types worldwide for which comparable data exist. Pan traps collected the highest proportion of the total bee species richness across all methods at the scale of a study site. Variable and standardized transect walks detected the highest total richness over all eight study sites. Trap nests and observation plots detected only a limited fraction of the bee species richness. To assess the total bee species richness in bee diversity hotspots, such as the studied habitats, we suggest a combination of transect walks conducted by trained bee collectors and pan trap sampling.

]]> Tue, 10 Mar 2015 11:00:00 +0200 http://www.step-project.net/files/DOWNLOAD/0912f50c711935e6d0000000.pdf 10 March 2015

Geographical patterns in prediction error of species distribution models

Aim  To describe and explain geographical patterns of false absence and false presence prediction errors that occur when describing current plant species ranges with species distribution models. Location  Europe. Methods  We calibrated species distribution models (generalized linear models) using a set of climatic variables and gridded distribution data for 1065 vascular plant species from the Atlas Florae Europaeae. We used randomly selected subsets for each species with a constant prevalence of 0.5, modelled the distribution 1000 times, calculated weighted averages of the model parameters and used these to predict the current distribution in Europe. Using a threshold of 0.5, we derived presence/absence maps. Comparing observed and modelled species distribution, we calculated the false absence rates, i.e. species wrongly modelled as absent, and the false presence rates, i.e. species wrongly modelled as present, on a 50 × 50 km grid. Subsequently, we related both error rates to species range properties, land use and topographic variability within grid cells by means of simultaneous autoregressive models to correct for spatial autocorrelation. Results  Grid-cell-specific error rates were not evenly distributed across Europe. The mean false absence rate was 0.16 ± 0.12 (standard deviation) and the mean false presence rate was 0.22 ± 0.13. False absence rates were highest in central Spain, the Alps and parts of south-eastern Europe, while false presence rates were highest in northern Spain, France, Italy and south-eastern Europe. False absence rates were high when range edges of species accumulated within a grid cell and when the intensity of human land use was high. False presence rates were positively associated with relative occurrence area and accumulation of range edges. Main conclusions  Predictions for various species are not only accompanied by species-specific but also by grid-cell-specific errors. The latter are associated with characteristics of the grid cells but also with range characteristics of occurring species. Uncertainties of predictive species distribution models are not equally distributed in space, and we would recommend accompanying maps of predicted distributions with a graphical representation of predictive performance.

]]> Tue, 10 Mar 2015 11:00:00 +0200 http://www.step-project.net/files/DOWNLOAD/Aebi&Neumann_2011_TREE.pdf 10 March 2015

Endosymbionts and honey bee colony losses?

Honey bees, Apis mellifera, are essential pollinators for the maintenance of natural biodiversity and agriculture [1]. Colony losses witnessed throughout the Northern hemisphere are therefore worrying [2], especially because no single driver has yet emerged as the definitive cause [3]. Interactions between viruses, ectoparasitic mites and microsporidian endoparasites are most likely key factors [3–5], but the underlying mechanisms are not well understood. Although it is known that maternally-inherited, facultative bacterial endosymbionts such as Wolbachia or Rickettsia can significantly interfere with viral and fungal infections of arthropods [6], they have so far been neglected in this regard.

]]> Tue, 10 Mar 2015 11:00:00 +0200 http://www.step-project.net/files/DOWNLOAD/Archer et al 2014 - Economic and ecological implications of geographic bias in pollination ecology.pdf 10 March 2015

Economic and ecological implications of geographic bias in pollinator ecology in the light of pollinator declines

Understanding the causes and consequences of pollinator declines is a priority in ecological research. However, across much of the globe we have a poor understanding of pollinator assemblages, population trends and the ecological and economic importance of particular pollinators, due to a marked geographic bias in research effort. Here, we show that almost half the data cited in thirteen recent meta-analyses, which ask important and diverse questions in pollination ecology, were collected in just five countries: Australia, Brazil, Germany, Spain and the USA. In contrast, the entire continent of Africa contributed only 4% of the data. We believe that the consequences of this geographic bias are severe. Foremost, pollinator assemblages (and possibly their sensitivity to ecological drivers) can greatly vary among these regions. In addition, many communities that rely on pollinators, bees in particular, for food security and wealth generation are in geographic regions where our understanding of pollination is poor. Collecting accurate information on pollinator populations in data deficient areas will allow us to identify vulnerable populations and species and so better target conservation measures. Moreover, it will help us to determine if our current understanding of pollinator losses, based on data collected in a few locations and on the species that predominate in those regions, is representative of the wide diversity of ecosystems. We propose means of collecting such data given socioeconomic constraints.

]]> Tue, 10 Mar 2015 11:00:00 +0200 http://www.step-project.net/files/DOWNLOAD/Bommarco_Oecologia_2012.pdf 10 March 2015

Insect pollination enhances seed yield, quality, and market value in oilseed rape

The relationships between landscape intensification, the abundance and diversity of pollinating insects, and their contributions to crop yield, quality, and market value are poorly studied, despite observed declines in wild and domesticated pollinators. Abundance and species richness of pollinating insects were estimated in ten fields of spring oilseed rape, Brassica napus var. SW Stratos™, located along a gradient of landscape compositions ranging from simple landscapes dominated by arable land to heterogeneous landscapes with extensive cover of semi-natural habitats. In each field, we assessed the contribution of wind and insect pollination to seed yield, seed quality (individual seed weight and oil and chlorophyll contents), and market value in a block experiment with four replicates and two treatments: (1) all flowers were accessible to insects, self and wind pollination, and (2) flowers enclosed in tulle net bags (mesh: 1 × 1 mm) were accessible only to wind and self pollination. Complex landscapes enhanced the overall abundance of wild insects as well as the abundance and species richness of hoverflies. This did not translate to a higher yield, probably due to consistent pollination by honey bees across all fields. However, the pollination experiment showed that insects increased seed weight per plant by 18% and market value by 20%. Seed quality was enhanced by insect pollination, rendering heavier seeds as well as higher oil and lower chlorophyll contents, clearly showing that insect pollination is required to reach high seed yield and quality in oilseed rape. Our study demonstrates considerable and previously underestimated contributions from pollinating insects to both the yield and the market value of oilseed rape.

]]> Tue, 10 Mar 2015 11:00:00 +0200 http://www.step-project.net/files/DOWNLOAD/BommarcoEtal2013TREE.pdf 10 March 2015

Ecological intensification: harnessing ecosystem services for food security

Rising demands for agricultural products will increase pressure to further intensify crop production, while negative environmental impacts have to be minimized. Ecological intensification entails the environmentally friendly replacement of anthropogenic inputs and/or enhancement of crop productivity, by including regulating and supporting ecosystem services management in agricultural practices. Effective ecological intensification requires an understanding of the relations between land use at different scales and the community composition of ecosystem service-providing organisms above and below ground, and the flow, stability, contribution to yield, and management costs of the multiple services delivered by these organisms. Research efforts and investments are particularly needed to reduce existing yield gaps by integrating context-appropriate bundles of ecosystem services into crop production systems.

]]> Tue, 10 Mar 2015 11:00:00 +0200 http://www.step-project.net/files/DOWNLOAD/chamberlainetal_ms_rev2.pdf 10 March 2015

Phylogenetic tree shape and the structure of mutualistic networks

Species community composition is known to alter the network of interactions between two trophic levels, potentially affecting its functioning (e.g. plant pollination success) and the stability of communities. Phylogenies vary in shape with regard to the rate of evolutionary change across a tree (influencing tree balance) and variation in the timing of branching events (affecting the distribution of node ages in trees), both of which may influence the structure of species interaction networks. Because related species are likely to share many of the traits that regulate interactions, the shape of phylogenetic trees may provide some insights into the distribution of traits within communities, and hence the likelihood of interaction among species. However, little attention has been paid to the potential effects of changes in phylogenetic diversity (PD) on interaction networks. Phylogenetic diversity is influenced by species diversity within a community, but also how distantly-related the constituent species are from one another. Here, we evaluate the relationship between two important measures of phylogenetic diversity (tree shape and age of nodes) and the structure of plant–pollinator interaction networks using empirical and simulated data. Whereas the former allows us to evaluate patterns in real communities, the latter allows us to evaluate more systematically the relationship between tree shape and network structure under three different models of trait evolution. In empirical networks, less balanced plant phylogenies were associated with lower connectance in interaction networks indicating that communities with the descendants of recent radiations are more diverged and specialized in their partnerships. In simulations, tree balance and the distribution of nodes through time were included in the best models for modularity, and the second best models for connectance and nestedness. In models assuming random evolutionary change through time (i.e. Brownian motion), less balanced trees and trees with nodes near the tips exhibited greater modularity, whereas in models with an early burst of radiation followed by relative stasis (i.e. early-burst models) more balanced trees and trees with nodes near roots had greater modularity. Synthesis. Overall, these results suggest that the shape of phylogenies can influence the structure of plant–pollinator interaction networks. However, the mismatch between simulations and empirical data indicate that no simple model of trait evolution mimics that observed in real communities.

]]> Tue, 10 Mar 2015 11:00:00 +0200 http://www.step-project.net/files/DOWNLOAD/Dainat et al 2012 CCD.pdf 10 March 2015

Colony collapse disorder in Europe

Colony collapse disorder (CCD) is a condition of honey bees, which has contributed in part to the recent major losses of honey bee colonies in the USA. Here we report the first CCD case from outside of the USA. We suggest that more standardization is needed for the case definition to diagnose CCD and to compare data on a global scale.

]]> Tue, 10 Mar 2015 11:00:00 +0200 http://www.step-project.net/files/DOWNLOAD/Dainat&Neumann_JIP_2013.pdf 10 March 2015

Colony collapse disorder (CCD) is a condition of honey bees, which has contributed in part to the recent major losses of honey bee colonies in the USA. Here we report the first CCD case from outside of the USA. We suggest that more standardization is need

The ectoparasitic mite Varroa destructor acting as a virus vector constitutes a central mechanism for losses of managed honey bee, Apis mellifera, colonies. This creates demand for an easy, accurate and cheap diagnostic tool to estimate the impact of viruliferous mites in the field. Here we evaluated whether the clinical signs of the ubiquitous and mite-transmitted deformed wing virus (DWV) can be predictive markers of winter losses. In fall and winter 2007/2008, A.m. carnica workers with apparent wing deformities were counted daily in traps installed on 29 queenright colonies. The data show that colonies which later died had a significantly higher proportion of workers with wing deformities than did those which survived. There was a significant positive correlation between V. destructor infestation levels and the number of workers displaying DWV clinical signs, further supporting the mite’s impact on virus infections at the colony level. A logistic regression model suggests that colony size, the number of workers with wing deformities and V. destructor infestation levels constitute predictive markers for winter colony losses in this order of importance and ease of evaluation.

]]> Tue, 10 Mar 2015 11:00:00 +0200 http://www.step-project.net/files/DOWNLOAD/Dalsgaard et al ECOGRAPHY 2013.pdf 10 March 2015

Historical climate-change influences modularity and nestedness of pollination networks

The structure of species interaction networks is important for species coexistence, community stability and exposure of species to extinctions. Two widespread structures in ecological networks are modularity, i.e. weakly connected subgroups of species that are internally highly interlinked, and nestedness, i.e. specialist species that interact with a subset of those species with which generalist species also interact. Modularity and nestedness are often interpreted as evolutionary ecological structures that may have relevance for community persistence and resilience against perturbations, such as climate-change. Therefore, historical climatic fluctuations could influence modularity and nestedness, but this possibility remains untested. This lack of research is in sharp contrast to the considerable efforts to disentangle the role of historical climate-change and contemporary climate on species distributions, richness and community composition patterns. Here, we use a global database of pollination networks to show that historical climate-change is at least as important as contemporary climate in shaping modularity and nestedness of pollination networks. Specifically, on the mainland we found a relatively strong negative association between Quaternary climate-change and modularity, whereas nestedness was most prominent in areasexperienced high Quaternary climate-change. On islands, Quaternary climate-change had weak effects on modularity and no effects on nestedness. Hence, for both modularity and nestedness, historical climate-change has left imprints on the network structure of mainland communities, but had comparably little effect on island communities. Our findings highlight a need to integrate historical climate fluctuations into eco-evolutionary hypotheses of network structures, such as modularity and nestedness, and then test these against empirical data. We propose that historical climate-change may have left imprints in the structural organisation of species interactions in an array of systems important for maintaining biological diversity.

]]> Tue, 10 Mar 2015 11:00:00 +0200 http://www.step-project.net/files/DOWNLOAD/Ecography_Hanspach_2014.pdf 10 March 2015

Host plant availability potentially limits butterfly distributions under cold environmental conditions

Species ranges are shaped by both climatic factors and interactions with other species. The stress gradient hypothesis predicts that under physiologically stressful environmental conditions abiotic factors shape range edges while in less stressful environments negative biotic interactions are more important. Butterflies provide a suitable system to test this hypothesis since larvae of most species depend on biotic interactions with a specific set of host plants, which in turn can shape patterns of occurrence and distribution. Here we modelled the distribution of 92 butterfly and 136 host plant species with three different modelling algorithms, using distribution data from the Swiss biodiversity monitoring scheme at a 1 × 1 km spatial resolution. By comparing the ensemble prediction for each butterfly species and the corresponding host plant(s), we assessed potential constraints imposed by host plant availability on distribution of butterflies at their distributional limits along the main environmental gradient, which closely parallels an elevational gradient. Our results indicate that host limitation does not play a role at the lower limit. At the upper limit 50% of butterfly species have a higher elevational limit than their primary host plant, and 33% have upper elevational limits that exceed the limits of both primary and secondary hosts. We conclude that host plant limitation was not relevant to butterfly distributional limits in less stressful environments and that distributions are more likely limited by climate, land use or antagonistic biotic interactions. Obligatory dependency of butterflies on their host plants, however, seems to represent an important limiting factor for the distribution of some species towards the cold, upper end of the environmental gradient, suggesting that biotic factors can shape ranges in stressful environments. Thus, predictions by the stress gradient hypothesis were not always applicable.

]]> Tue, 10 Mar 2015 11:00:00 +0200 http://www.step-project.net/files/DOWNLOAD/Ecological characteristics associated with high mobility in.pdf 10 March 2015

Species ranges are shaped by both climatic factors and interactions with other species. The stress gradient hypothesis predicts that under physiologically stressful environmental conditions abiotic factors shape range edges while in less stressful environ

Mobility is an important factor influencing the range and persistence of local populations. However, mobility is very difficult to measure empirically and thus is poorly known in most taxa. Since ecological characteristics have been suggested as good estimators of mobility, we here explore the association between ecological characteristics and mobility. We surveyed night-active moths on a Swedish island, situated 16 km from the mainland, and compared ecological characteristics of the non-resident moths found on the island with those of a species pool of assumed potential vagrants from the neighbouring mainland. Species associated with high mobility were characterised by a large range, a high population density, an activity period during warm temperatures and by being habitat generalists or preferring open habitats. The generally assumed view of poly- and oligophagous species being more mobile than monophagous species was obscured by the effect of population density. Poly- and oligophagous species had higher population densities than did monophagous species, which probably explain their higher mobility found in this study. Our result highlights the need to consider the influence of ecological characteristics on mobility. This in turn will have implications for an increased understanding of distribution patterns, population persistence and how to prioritise conservation actions, especially since habitats and climate are under dramatic changes. In taxa where data on mobility are poor, ecological characteristics can be used as a proxy for mobility.

]]> Tue, 10 Mar 2015 11:00:00 +0200 http://www.step-project.net/files/DOWNLOAD/fauser-misslin 2014.pdf 10 March 2015

Mobility is an important factor influencing the range and persistence of local populations. However, mobility is very difficult to measure empirically and thus is poorly known in most taxa. Since ecological characteristics have been suggested as good esti

Mobility is an important factor influencing the range and persistence of local populations. However, mobility is very difficult to measure empirically and thus is poorly known in most taxa. Since ecological characteristics have been suggested as good estimators of mobility, we here explore the association between ecological characteristics and mobility. We surveyed night-active moths on a Swedish island, situated 16 km from the mainland, and compared ecological characteristics of the non-resident moths found on the island with those of a species pool of assumed potential vagrants from the neighbouring mainland. Species associated with high mobility were characterised by a large range, a high population density, an activity period during warm temperatures and by being habitat generalists or preferring open habitats. The generally assumed view of poly- and oligophagous species being more mobile than monophagous species was obscured by the effect of population density. Poly- and oligophagous species had higher population densities than did monophagous species, which probably explain their higher mobility found in this study. Our result highlights the need to consider the influence of ecological characteristics on mobility. This in turn will have implications for an increased understanding of distribution patterns, population persistence and how to prioritise conservation actions, especially since habitats and climate are under dramatic changes. In taxa where data on mobility are poor, ecological characteristics can be used as a proxy for mobility.

]]> Tue, 10 Mar 2015 11:00:00 +0200 http://www.step-project.net/files/DOWNLOAD/Gagic_et_al_2015_Proc_R_Soc_B_282.pdf 10 March 2015

Functional identity and diversity of animals predict ecosystem functioning better than species-based indices

Drastic biodiversity declines have raised concerns about the deterioration of ecosystem functions and have motivated much recent research on the relationship between species diversity and ecosystem functioning. A functional trait framework has been proposed to improve the mechanistic understanding of this relationship, but this has rarely been tested for organisms other than plants. We analysed eight datasets, including five animal groups, to examine how well a trait-based approach, compared with a more traditional taxonomic approach, predicts seven ecosystem functions below- and above-ground. Trait-based indices consistently provided greater explanatory power than species richness or abundance. The frequency distributions of single or multiple traits in the community were the best predictors of ecosystem functioning. This implies that the ecosystem functions we investigated were underpinned by the combination of trait identities (i.e. single-trait indices) and trait complementarity (i.e. multi-trait indices) in the communities. Our study provides new insights into the general mechanisms that link biodiversity to ecosystem functioning in natural animal communities and suggests that the observed responses were due to the identity and dominance patterns of the trait composition rather than the number or abundance of species per se.

]]> Tue, 10 Mar 2015 11:00:00 +0200 http://www.step-project.net/files/DOWNLOAD/Gosselin_et_al_2013_Does-Aconitum-septentrionale-chemically-protect-floral-rewards-to-the-advantage-of-specialist-bumblebees_2013_Ecological-Entomology.pdf 10 March 2015

Does Aconitum septentrionale chemically protect floral rewards to the advantage of specialist bumblebees?

Chemical protection of plants against herbivory is a well-studied phenomenon. However, chemical protection of floral rewards remains relatively unexplored. As with herbivore–plant interactions, toxic rewards may impact generalist and specialist foragers in different ways. This study focuses on the toxic plant Aconitum septentrionale (Ranunculaceae). This plant is visited by specialist and generalist bumblebees. Alkaloid concentrations and profiles for the different parts of A. septentrionale were analysed to detect a potential chemical toxicity of floral rewards. In the same way, sequestration of alkaloids was tested on a pollen specialist species Bombus consobrinus and a generalist species Bombus wurflenii. A liquid chromatography-quadrupole time-of-flight mass spectrometry method was developed to discriminate 16 major compounds in the plant. These alkaloids were present in all parts of the plant, but in different ratios. The concentration was high in the roots but also in pollen, providing evidence of chemical protection of this reward. By contrast, nectar had the lowest concentration of alkaloids. Only six alkaloids were detected in B. consobrinus tissues, at trace levels. For the generalist bumblebee B. wurflenii, no traces of alkaloids were detected. Lappaconitine was the major alkaloid compound in pollen, nectar and B. consobrinus tissues. Low accumulation of alkaloids in B. consobrinus tissues could be an ecological advantage for this specialist species in terms of pathogen and predatory avoidance.

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