Evidence for declining populations of both wild and managed bees has raised concern about a potential global pollination crisis. Strategies to mitigate bee loss generally aim to enhance floral ...resources. However, we do not really know whether loss of preferred floral resources is the key driver of bee decline because accurate assessment of host plant preferences is difficult, particularly for species that have become rare. Here we examine whether population trends of wild bees in The Netherlands can be explained by trends in host plants, and how this relates to other factors such as climate change. We determined host plant preference of bee species using pollen loads on specimens in entomological collections that were collected before the onset of their decline, and used atlas data to quantify population trends of bee species and their host plants. We show that decline of preferred host plant species was one of two main factors associated with bee decline. Bee body size, the other main factor, was negatively related to population trend, which, because larger bee species have larger pollen requirements than smaller species, may also point toward food limitation as a key factor driving wild bee loss. Diet breadth and other potential factors such as length of flight period or climate change sensitivity were not important in explaining twentieth century bee population trends. These results highlight the species-specific nature of wild bee decline and indicate that mitigation strategies will only be effective if they target the specific host plants of declining species.
Significance Growing concern about bee declines and associated loss of pollination services has increased the urgency to identify the underlying causes. So far, the identification of the key drivers of decline of bee populations has largely been based on speculation. We assessed the relative importance of a range of proposed factors responsible for wild bee decline and show that loss of preferred host plant species is one of the main factors associated with the decline of bee populations in The Netherlands. Interestingly, species foraging on crop plant families have stable or increasing populations. These results indicate that mitigation strategies for loss of wild bees will only be effective if they target the specific host plants of declining bee species.
Functional diversity within communities may influence ecosystem functioning, but which factors drive functional diversity? We hypothesize that communities assembled from many phylogenetic lineages ...show large functional diversity if assembly is random, but low functional diversity if assembly is controlled by interactions between species within lineages. We combined > 9000 descriptions of Dutch plant communities, a species-level phylogeny, and information on 16 functional traits (including eight dispersal traits). We found that all traits were conserved within lineages, but nevertheless communities assembled from many lineages showed a smaller variation in trait-states of most traits (including dispersal traits) than communities assembled from few lineages. Hence, within lineages, species are not randomly assembled into communities, contradicting Neutral Theory. In fact, we find evidence for evolutionary divergence in trait-states as well as present-day mutual exclusion among related, similar species, suggesting that functional diversity of communities increased due to past and present interactions between species within lineages.
How plant species diversity can mediate the temporal stability of ecosystem functioning during periods of environmental stress is still a pressing question in ecology, certainly in the context of ...predicted increasing frequencies and intensities of climate extremes, such as drought. The vast majority of empirical research in this context is based on relatively small-scaled experiments, where plant species composition is manipulated and ecosystem functions, such as biomass production, are monitored through time. Results of these studies have generally shown that ecosystem functioning is more stable in more species-diverse communities. Yet, there is very little evidence so far that these relations also hold in naturally assembled plant communities. In this study, we combined historical vegetation and climate data with time series of remotely sensed indicators of aboveground biomass production (MODIS NDVI), to quantify how plant species diversity and plant functional diversity correlate with the temporal stability of biomass production in naturally assembled Dutch dune grasslands under the influence of fluctuating drought. We found that the negative NDVI response to drought of grasslands with a higher plant species richness and diversity was significantly lower than the response of less species rich and species-diverse grasslands, indicating a stabilizing role of plant species richness and diversity on biomass production through time. We found no relation between plant functional diversity and NDVI response to drought. This is the first study to generalize experimentally established relations between species diversity and stability of ecosystem functioning to naturally assembled grasslands across a large spatial and temporal scale.
The ongoing decline of many plant species in Northwest Europe indicates that traditional conservation measures to improve the habitat quality, although useful, are not enough to halt diversity ...losses. Using recent databases, we show for the first time that differences between species in adaptations to various dispersal vectors, in combination with changes in the availability of these vectors, contribute significantly to explaining losses in plant diversity in Northwest Europe in the 20th century. Species with water‐ or fur‐assisted dispersal are over‐represented among declining species, while others (wind‐ or bird‐assisted dispersal) are under‐represented. Our analysis indicates that the ‘colonization deficit’ due to a degraded dispersal infrastructure is no less important in explaining plant diversity losses than the more commonly accepted effect of eutrophication and associated niche‐based processes. Our findings call for measures that aim to restore the dispersal infrastructure across entire regions and that go beyond current conservation practices.
Question: How many vegetation plot observations (relevés) are available in electronic databases, how are they geographically distributed, what are their properties and how might they be discovered ...and located for research and application? Location: Global. Methods: We compiled the Global Index of Vegetation-Plot Databases (GIVD; http://www.givd.info), an Internet resource aimed at registering metadata on existing vegetation databases. For inclusion, databases need to (i) contain temporally and spatially explicit species co-occurrence data and (ii) be accessible to the scientific public. This paper summarizes structure and data quality of databases registered in GIVD as of 30 December 2010. Results: On the given date, 132 databases containing more than 2.4 million non-overlapping plots had been registered in GIVD. The majority of these data were in European databases (83 databases, 1.6 million plots), whereas other continents were represented by substantially less (North America 15, Asia 13, Africa nine, South America seven, Australasia two, multi-continental three). The oldest plot observation was 1864, but most plots were recorded after 1970. Most plots reported vegetation on areas of 1 to 1000 m2; some also stored time-series and nested-plot data. Apart from geographic reference (required for inclusion), most frequent information was on altitude (71%), slope aspect and inclination (58%) and land use (38%), but rarely soil properties (<7%). Conclusions: The vegetation plot data in GIVD constitute a major resource for biodiversity research, both through the large number of species occurrence records and storage of species co-occurrence information at a small scale, combined with structural and plot-based environmental data. We identify shortcomings in available data that need to be addressed through sampling under-represented geographic regions, providing better incentives for data collection and sharing, developing user-friendly database exchange standards, as well as tools to analyse and remove confounding effects of sampling biases. The increased availability of data sets conferred by registration in GIVD offers significant opportunities for large-scale studies in community ecology, macroecology and global change research.
Question
When evaluating forests in terms of their biodiversity, distinctiveness and naturalness, the affinity of the constituent species to forests is a crucial parameter. Here we ask to what extent ...are vascular plant species associated with forests, and does species’ affinity to forests vary between European regions?
Location
Temperate and boreal forest biome of Northwestern and Central Europe.
Methods
We compiled EuForPlant, a new extensive list of forest vascular plant species in 24 regions spread across 13 European countries using vegetation databases and expert knowledge. Species were region‐specifically classified into four categories reflecting the degree of their affinity to forest habitats: 1.1, species of forest interiors; 1.2, species of forest edges and forest openings; 2.1, species that can be found in forest as well as open vegetation; and 2.2, species that can be found partly in forest, but mainly in open vegetation. An additional “O” category was distinguished, covering species typical for non‐forest vegetation.
Results
EuForPlant comprises 1,726 species, including 1,437 herb‐layer species, 159 shrubs, 107 trees, 19 lianas and 4 epiphytic parasites. Across regions, generalist forest species (with 450 and 777 species classified as 2.1 and 2.2, respectively) significantly outnumbered specialist forest species (with 250 and 137 species classified as 1.1 and 1.2, respectively). Even though the degree of shifting between the categories of forest affinity among regions was relatively low (on average, 17.5%), about one‐third of the forest species (especially 1.2 and 2.2) swapped categories in at least one of the study regions.
Conclusions
The proposed list can be used widely in vegetation science and global change ecology related to forest biodiversity and community dynamics. Shifting of forest affinity among regions emphasizes the importance of a continental‐scale forest plant species list with regional specificity.
We compiled a new list of forest vascular plant species spread in large parts of the European temperate and boreal forest biome using vegetation databases and expert knowledge. Species were region‐specifically classified into four categories reflecting the degree of their affinity to forest habitats. EuForPlant can be used widely in vegetation ecology related to forest biodiversity and community dynamics.
Over the past half century, nature protection in the European Union has been increasingly controlled by commitments to policy and legislative frames, notably the Habitats Directive, originating from ...the European Union and adopted by an enlarging constituency of member states. Habitat (or biotope) classifications developed in association with these policies, first the Palaearctic habitat classification and CORINE, then the EUNIS habitat classification, have provided typologies with definitions of habitat types intended to aid their recognition, mapping, protection and monitoring. Phytosociological expertise and classifications of formally defined plant communities or syntaxa have played a part in the development of these typologies and in interpretation of the Habitats Directive from the start, though this involvement has been complex and sometimes unclear. This paper catalogues this history and shows how the development of increasingly robust definitions of EUNIS habitat types, an overarching European framework of phytosociological syntaxa and very substantial point-source data (relevés) are converging to aid the interpretation and delivery of environmental policy. In particular, crosswalks between EUNIS habitat types and syntaxa, lists of constant, differential and dominant species, standardised habitat descriptions as well as distribution, predictive and indicative maps are now becoming available. The European Red List of Habitats, also based on the EUNIS typology, provides images and other complementary information on distribution, pressures and threats and a Red List assessment. A comprehensive factsheet with complementary fuller environmental parameterisation for each EUNIS habitat type remains a realistic goal.
Aims: Although many phytosociological studies have provided detailed local and regional descriptions of coastal dune vegetation, a unified classification of this vegetation in Europe and the ...Mediterranean Basin has been missing. Our aim is to produce a formalized classification of this vegetation and to identify the main factors driving its plant species composition at a continental scale. Location: Atlantic and Baltic coasts of Europe, Mediterranean Basin and the Black Sea region. Methods: We compiled a database of 30,759 plots of coastal vegetation, which were resampled to reduce unbalanced sampling effort, obtaining a data set of 11,769 plots. We classified these plots with TWINSPAN, interpreted the resulting clusters and used them for developing formal definitions of phytosociological alliances of coastal dune vegetation, which were included in an expert system for automatic vegetation classification. We related the alliances to climatic factors and described their biogeographic features and their position in the coastal vegetation zonation. We examined and visualized the floristic relationships among these alliances by means of DCA ordination. Results: We defined 18 alliances of coastal dune vegetation, including the newly described Centaureo cuneifoliae-Verbascion pinnatifidi from the Aegean region. The main factors underlying the differentiation of these alliances were biogeographic and macroclimatic contrasts between the Atlantic-Baltic, Mediterranean and Black Sea regions, along with ecological differences between shifting and stable dunes. The main difference in species composition was between the Atlantic–Baltic and Mediterranean–Black Sea regions. Within the former region, the main difference was driven by the different ecological conditions between shifting and stable dunes, whereas within the latter, the main difference was biogeographic between the Mediterranean and the Black Sea. Conclusions: The first formal classification of the European coastal dune vegetation was established, accompanied by an expert system containing the formal definitions of alliances, which can be applied to new data sets. The new classification system critically revised the previous concepts and integrated them into a consistent framework, which reflects the main gradients in species composition driven by biogeographic influences, macroclimate and the position of the sites in the coast–inland zonation of the dune systems. A revision of the class concept used in EuroVegChecklist is also proposed.
Ecological intensification of agriculture (EI) aims to conserve and promote biodiversity and the sustainable use of associated ecosystem services to support resourceâefficient production. In many ...cases EI requires fundamental changes in farm and landscape management as well as the organizations and institutions that support agriculture. Ecologists can facilitate EI by engaging with stakeholders and, in the process, by generating âactionable knowledgeâ (that is, knowledge that specifically supports stakeholder decision making and consequent actions). Using three case studies as examples, we propose four principles whereby science can improve the delivery of actionable knowledge for EI: (1) biodiversity conservation helps to ensure the delivery of ecosystem services, (2) management of ecosystem services benefits from a landscapeâscale approach, (3) ecosystem service tradeâoffs and synergies need to be articulated, and (4) EI is associated with complex social dynamics involving farmers, governments, researchers, and related institutions. These principles have the potential to enhance adoption of EI, but institutional and policy challenges remain.
Alien species can be a major threat to ecological communities, but we do not know why some community types allow the entry of many more alien species than do others. Here, for the first time, we ...suggest that evolutionary diversity inherent to the constituent species of a community may determine its present receptiveness to alien species. Using recent large databases from observational studies, we find robust evidence that assemblage of plant community types from few phylogenetic lineages (in plots without aliens) corresponds to higher receptiveness to aliens. Establishment of aliens in phylogenetically poor communities corresponds to increased phylogenetic dispersion of recipient communities and to coexistence with rather than replacement of natives. This coexistence between natives and distantly related aliens in recipient communities of low phylogenetic dispersion may reflect patterns of trait assembly. In communities without aliens, low phylogenetic dispersion corresponds to increased dispersion of most traits, and establishment of aliens corresponds to increased trait concentration. We conclude that if quantified across the tree of life, high biodiversity correlates with decreasing receptiveness to aliens. Low phylogenetic biodiversity, in contrast, facilitates coexistence between natives and aliens even if they share similar trait states.
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