Search

Aim: Global change, especially landscape simplification, is a main driver of species loss that can alter ecological interaction networks, with potentially severe consequences to ecosystem functions. Therefore, understanding how landscape simplification affects the rate of loss of plant–pollinator interaction diversity (i.e., number of unique interactions) compared to species diversity alone, and the role of persisting abundant pollinators, is key to assess the consequences of landscape simplification on network stability and pollination services. Location: France, Germany, and Switzerland. Methods: We analysed 24 landscape‐scale plant–pollinator networks from standardised transect walks along landscape simplification gradients in three countries. We compared the rates of species and interaction diversity loss along the landscape simplification gradient and then stepwise excluded the top 1%–20% most abundant pollinators from the data set to evaluate their effect on interaction diversity, network robustness to secondary loss of species, and flower visitation frequencies in simplified landscapes. Results: Interaction diversity was not more vulnerable than species diversity to landscape simplification, with pollinator and interaction diversity showing similar rates of erosion with landscape simplification. We found that 20% of both species and interactions are lost with an increase of arable crop cover from 30% to 80% in a landscape. The decrease in interaction diversity was partially buffered by persistent abundant generalist pollinators in simplified landscapes, which were nested subsets of pollinator communities in complex landscapes, while plants showed a high turnover in interactions across landscapes. The top 5% most abundant pollinator species also contributed to network robustness against secondary species loss but could not prevent flowers from a loss of visits in simplified landscapes. Main Conclusions: Although persistent abundant pollinators buffered the decrease in interaction diversity in simplified landscapes and stabilised network robustness, flower visitation frequency was reduced, emphasising potentially severe consequences of further ongoing land‐use change for pollination services. [ABSTRACT FROM AUTHOR]

Aim: Conventional species distribution models (SDMs) usually focus on the species level but disregard intraspecific variability. Phylogeographic structure and evolutionary significant units (ESU) have been proposed as pragmatic proxies to incorporate intraspecific differentiation in SDMs. Nevertheless, the efficiency of using these proxies in SDMs has been poorly investigated. We analysed how the projections of current and future climatically suitable areas can be affected when using ESU‐based or lineage‐based models compared to a species‐level model. Location: West‐Palaearctic region. Methods: As examples, we used three bumblebee species (133,787 observations). We assessed potential climatic niche differentiation between species level, lineages and ESUs, by determining the niche position and niche breadth for each classification level by outlying mean index analyses. Subsequently, we developed SDMs for each species and classification level separately using boosted regression trees prior to a comparison of their performances. Finally, we used the alternative models to project the extent of climatically suitable areas in 2070. Results: We found that in spite of highly similar overall model accuracy, integrating intraspecific variability significantly increases model sensitivity (i.e., better predicting presences) while decreased model specificity (i.e., over‐predicting the range). Consequently, both predictions of current and projections of future suitable conditions differed among the three approaches. Main conclusions: We showed that although integrating lineage or ESU information did not improve the accuracy of conventional species‐level SDMs, it led to considerably different conclusions. As SDM‐based climatic risk assessments are increasingly used to help and improve conservation plans, divergences and limitations of each modelling approach should be taken into account for developing efficient biodiversity management strategies. Lineage and ESU‐based SDMs offer the advantage to draw attention to species in which allopatric populations could display physiologically different responses to climate change when they lead to different results than species‐based models. [ABSTRACT FROM AUTHOR]

Aim: To assess the effectiveness of protected areas in preventing biodiversity decline. We first test whether species richness of butterfly assemblages is higher within European Natura 2000 (N2000) sites than in their surroundings. We then assess temporal trends in butterfly richness and test whether these trends differ inside and outside the N2000 network. Location: Germany, Europe. Methods: We utilized generalized linear mixed‐effects models (GLMM) to analyse an 11‐year data series on species richness of butterfly assemblages collected on 245 transects across Germany, located inside and outside N2000 sites, and comprising a total of 122 butterfly species. Results: Butterfly species richness was highest inside N2000 protected areas, while outside it constantly declined with increasing distance from N2000 sites. We found an overall decline in species richness by 10% within 11 years. This decline neither differed between transects located inside or outside the N2000 network nor varied with distance from N2000 sites. Main conclusions: The higher species richness inside the N2000 network underlines their proper designation and their potential for the conservation of biodiversity. However, the current negative trend in butterfly species richness across Germany is not mitigated by the N2000 network, and we assume insufficient management or measures targeted at other organisms than butterflies as potential reasons. [ABSTRACT FROM AUTHOR]

Aim Species distribution models built with geographically restricted data often fail to capture the full range of conditions experienced by species across their entire distribution area. Using such models to predict distribution shifts under future environmental change may, therefore, produce biased projections. However, restricted-scale models have the potential to include a larger sample of taxa for which distribution data are available and to provide finer-resolution projections that are better applied to conservation planning than the forecasts of broad-scale models. We examine the circumstances under which the projected shifts in species richness patterns derived from restricted-scale and broad-scale models are most likely to be similar. Location Europe. Methods The distribution of butterflies in Finland, Belgium/Netherlands and Spain was modelled based on restricted-scale (local) and broad-scale (continental) distribution and climate data. Both types of models were projected under future climate change scenarios to assess potential changes in species richness. Results In Finland, species richness was projected to increase strongly based on restricted-scale models and to decrease slightly with broad-scale models. In Belgium/Netherlands, restricted-scale models projected a larger decrease in richness than broad-scale models. In Spain, both models projected a slight decrease in richness. We obtained similar projections based on restricted-scale and broad-scale models only in Spain because the climatic conditions available here covered the warm part of the distributions of butterflies better than in Finland and Belgium/Netherlands. Main conclusions Restricted-scale models that fail to capture the warm part of species distributions produce biased estimates of future changes in species richness when projected under climatic conditions with no modern analogue in the study area. We recommend the use of distribution data beyond the boundaries of the study area to capture the part of the species response curves reflecting the climatic conditions that will prevail within that area in the future. [ABSTRACT FROM AUTHOR]

Aim Agricultural intensification and urbanization are important drivers of biodiversity change in Europe. Different aspects of bee community diversity vary in their sensitivity to these pressures, as well as independently influencing ecosystem service provision (pollination). To obtain a more comprehensive understanding of human impacts on bee diversity across Europe, we assess multiple, complementary indices of diversity. Location One Thousand four hundred and forty six sites across Europe. Methods We collated data on bee occurrence and abundance from the published literature and supplemented them with the PREDICTS database. Using Rao's Quadratic Entropy, we assessed how species, functional and phylogenetic diversity of 1,446 bee communities respond to land-use characteristics including land-use class, cropland intensity, human population density and distance to roads. We combined these models with statistically downscaled estimates of land use in 2005 to estimate and map-at a scale of approximately 1 km2-the losses in diversity relative to semi-natural/natural baseline (the predicted diversity of an uninhabited grid square, consisting only of semi-natural/natural vegetation). Results We show that-relative to the predicted local diversity in uninhabited semi-natural/natural habitat-half of all EU27 countries have lost over 10% of their average local species diversity and two-thirds of countries have lost over 5% of their average local functional and phylogenetic diversity. All diversity measures were generally lower in pasture and higher-intensity cropland than in semi-natural/natural vegetation, but facets of diversity showed less consistent responses to human population density. These differences have led to marked spatial mismatches in losses: losses in phylogenetic diversity were in some areas almost 20 percentage points (pp.) more severe than losses in species diversity, but in other areas losses were almost 40 pp. less severe. Main conclusions These results highlight the importance of exploring multiple measures of diversity when prioritizing and evaluating conservation actions, as species-diverse assemblages may be phylogenetically and functionally impoverished, potentially threatening pollination service provision. [ABSTRACT FROM AUTHOR]

Aim Biological invasions are today the second-largest global threat for biodiversity. Once introduced, exotic plant species can modify ecosystem composition, structure and dynamics, eventually driving native species to local extinction. Among the groups of organisms, most likely to be directly affected by exotic invasive plants are herbivorous insects, such as butterflies, which strongly depend on plants throughout their life cycle. However, it remains unclear whether invasive plants have a negative or a positive effect on butterfly diversity at a landscape scale. Location Switzerland. Methods Using an extensive inventory (393 sites across Switzerland) of both butterfly and invasive plants, we explore the impact of 31 invasive black listed plant species on local butterfly richness. We further identify each butterfly species' response to invasive plants (i.e. positive, neutral or negative) and analyse the functional and phylogenetic characteristics of these different groups of species. Results Our results indicate that butterfly richness negatively correlates with an increase in invasive plant richness. When studying the individual response of each butterfly species to the number of invasive plants, we found that no single butterfly is profiting from invasive plant species, while 28 butterfly species (24%) suffer from the presence of invasive plants. We further show that the species negatively affected are on average less mobile than the unaffected species and that they are phylogenetically clustered. Main conclusions Our results present evidences of the influence of invasive species on other trophic levels and interaction networks. We further highlight that a lack of management efforts for mitigating invasive plant impacts threatens specific sections of the functional and phylogenetic diversity of butterflies. [ABSTRACT FROM AUTHOR]

Aim To quantify spatio-temporal changes in species richness and assemblage composition of Danish butterflies over more than 100 years and to assess whether different functional groups of butterflies show different temporal trajectories. Location Denmark, Europe. Methods We applied species accumulation curves to estimate relative species richness changes from unequally sampled occurrence records, collected over more than a century (1900-2012), at local (i.e. 10 km× 10 km) and regional (country-wide) spatial scales. Furthermore, we calculated similarity in species composition between 10 km× 10 km grid cells to evaluate changes in assemblage composition (i.e. biotic homogenization) of butterflies through space and time. Trends were evaluated for all butterflies as well as for three functional groups, using hierarchical clustering and species-specific values of eight ecological traits. Results We document severe declines in butterfly diversity over the last century, with substantial regional-scale extinctions leading to a net loss of 10% of all Danish butterfly species. Segregating species into functional groups showed that the highest rate of regional extinction occurred among sedentary habitat specialists overwintering in the egg stage, while the most severe local-scale declines occurred among sedentary host plant specialists overwintering in the larval stage. In contrast, mobile generalist species with mature overwintering stages showed stable richness trends throughout the century. However, a pervasive spatio-temporal biotic homogenization of butterfly assemblages was revealed for all functional groups. Main conclusions Our results suggest that observed changes in species richness were driven by a gradual replacement of ecological specialists by broadly adapted ecological generalists. In addition to drawing attention to a severe long-term impoverishment of the Danish butterfly fauna, our results suggest that trajectories of butterfly species richness and assemblage composition over the last century are related to multiple functional traits, highlighting the need to consider different aspects of ecological specialization when assessing extinction risk. [ABSTRACT FROM AUTHOR]

The cover image, by LAURE GALLIEN et al., is based on the Biodiversity Research Invasive plants threaten the least mobile butterflies in Switzerland, DOI: 10.1111/ddi.12513. [ABSTRACT FROM AUTHOR]