Search

Aim: We explored the range shifts of alien and native birds, the responses of alien and native β‐diversity to abiotic factors, and the effect of native diversity on alien β‐diversity in two time periods. Location: Great Britain. Time period: 1968–1972, 2007–2011. Taxa studied: Breeding birds. Methods: We estimated range shifts of alien and native species between the periods 1968–1972 and 2007–2011. Following, β‐diversity of alien and native communities was estimated by Jaccard pairwise index (βtot) and partitioned into richness difference and replacement component for each period. We built abiotic generalized dissimilarity models including abiotic factors for alien and native βtot and their components and a biotic model for aliens including native taxonomic and functional diversity as predictors. Results: Most alien and half native species expanded into new regions during the 40‐year period. The native species range shifts did not exhibit a clear pattern along the longitudinal or latitudinal gradient, while alien species tended to move north‐westwards. The richness difference was the dominant component of alien β‐diversity, and the replacement component contributed mostly to native β‐diversity. Alien β‐diversity responded similarly but less strongly than native β‐diversity, to the abiotic gradients. Temperature‐related variables, distance and precipitation were the most important abiotic drivers of native and alien β‐diversity. The biotic model of alien β‐diversity explained more deviance than the abiotic model. Main conclusions Alien species expanded into new regions over the 40 years, with alien β‐diversity driven mostly by species gains. The effect of environmental filtering on alien communities was weaker compared with native communities but was slightly reinforced in the second period compared with the first period, highlighting the role of environmental change in shaping diversity patterns. Native diversity played a key role in driving alien β‐diversity, through biotic interactions or/and by reflecting climatic suitability or niche availability for aliens. [ABSTRACT FROM AUTHOR]

Assessing spatial and temporal patterns of biodiversity change is essential to understand how communities vary over time and confront to environmental changes for the resilience of ecosystem functioning. We use data from two bird atlases of Britain collected during the breeding periods 1988–1991 and 2008–2011 to measure temporal β‐diversity of taxonomic, functional and phylogenetic dimensions and examine the relationship and the level of congruence of the three dimensions of temporal β‐diversity and their respective partitioned components (turnover‐nestedness). Temporal β‐diversity, turnover and nestedness patterns were highly congruent for the taxonomic and phylogenetic dimension, although these dimensions were weakly associated with the functional dimension. We found higher levels of temporal changes for the taxonomic (mean Jaccard β‐diversity 0.27) and phylogenetic (mean Jaccard β‐diversity 0.21) dimensions than for the functional dimension (mean Jaccard β‐diversity 0.09), implying that despite the changes in species composition the functional composition of the communities remained less affected. For taxonomic and phylogenetic dimensions, turnover contributed more than nestedness to shaping β‐diversity, while for functional β‐diversity the two components contributed similarly. Communities at higher altitudes were also more functionally similar in 20 years but with more changes in taxonomic and phylogenetic diversity possibly due to environmental filtering. We hypothesize that the low congruence might be due to species with extreme trait values persisting throughout time and retaining the volume of functional space and thus contributing to the low temporal change of functional diversity despite the high levels of change in species composition, perhaps an indication of functional "stability." [ABSTRACT FROM AUTHOR]

Amphibians are among the most endangered group of vertebrates. To conserve their diversity we need to comprehend how functional diversity and species traits vary across environmental gradients. We investigate the distribution of functional diversity (functional richness–functional dispersion–functional evenness) and the environmental drivers (climate, energy availability, landscape and anthropogenic attributes) of these patterns for the 68 amphibian species of Europe using generalized least squares models and hierarchical partitioning. Based on eight functional traits, species were arranged in a multidimensional functional trait space and principal coordinates analysis (PCoA) was applied to investigate the occupancy of this space by amphibians. Functional richness mirrored species richness pattern and decreased towards higher latitudes; while, functional dispersion showed an even stronger negative correlation with latitude. Functional evenness did not display a clear latitudinal trend. Areas with higher functional richness and functional dispersion are associated with lower temperature seasonality and increased land cover diversity, in contrast areas with higher functional evenness are characterized by lower mean annual temperature. Climate seasonality mostly influenced the traits related to the first two PCoA axes (i.e., foraging location, mobility mode) which could have been considered as functional response traits and could be used as indicators to examine how communities respond to environmental change. Our work describes the macroecological patterns and discusses the relative importance of alternative underlying mechanisms driving functional diversity of this high‐risk taxonomical group and highlight that species richness presents only part of the biodiversity patterns, while other facets like functional evenness behave distinctively differently. [ABSTRACT FROM AUTHOR]

Trait‐based approaches and functional diversity have been previously used to enlighten our knowledge on the structure of community assemblages which are driven by species interactions or abiotic factors. We assess what amphibian functional diversity implies for the community assembly of amphibians of Europe and whether the use of different Functional Trait Groups (FTGs) affects the results. We used presence/absence atlas with 50 km × 50 km grain size and three functional diversity indices (FRic, RaoQ and FDiv) which reflect functional richness and divergence to estimate functional diversity patterns calculated for three FTGs: Morphological, Habitat‐related, Reproductive and the complete set of traits. To identify the two key processes (environmental filtering and limiting similarity) that may shape amphibian communities and how the relative importance of these processes could change using different FTGs, we used null models to test for non‐random patterns of functional diversity accounting or not for the difference in regional species pool. We show that for the same grid cell, for one FTG we might observe lower than randomly expected functional diversity (i.e., trait convergence or environmental filtering as the dominant community assembly process) while for another FTG or for the complete set of traits, higher than randomly expected functional diversity (i.e., trait divergence or limiting similarity as the dominant community assembly process). This highlights the role of trait selection on the inference drawn regarding community assembly. Furthermore, the number of traits (complete set vs. FTGs) used to quantify functional diversity also affects the conclusions regarding community assembly. We assess what amphibian functional diversity implies for the community assembly of amphibians of Europe and whether the use of different Functional Trait Groups (FTGs) affect the results. We show that for the same grid cell, for one FTG we might observe lower than randomly expected functional diversity (i.e. trait convergence or environmental filtering as the dominant community assembly process) while for another FTG or for the complete set of traits, higher than randomly expected functional diversity (i.e. trait divergence or limiting similarity as dominant community assembly process). [ABSTRACT FROM AUTHOR]

Questions Do the mechanisms driving community assembly differ between two islands of different age and history of vegetation development? How does sampling scale affect the strength that each assembly mechanism poses on the assembly of plant communities? Location Volcanic islands (Palea Kameni and Nea Kameni) of Santorini Archipelago, Greece. Methods Functional diversity has been proposed as a framework for discriminating among mechanisms of community assembly, such as habitat filtering, limiting similarity and random assembly. We investigated four plant communities in two sea-born volcanic islands. We recorded plant diversity at scales from 1 m2 to 64 m2. We calculated three indices of functional diversity: functional richness, functional evenness and functional divergence, using 26 functional traits (including vegetative characteristics, ecological preferences and regenerative characteristics). We used null model analysis to test for two different assembly mechanisms: habitat filtering and limiting similarity or random assembly. Results The assemblage of the four communities was complex and did not follow a single mechanism. In most cases, finer-scale patterns indicated randomness, while coarser scales revealed more structured communities. In the older island, the scrub community was mainly defined by limiting similarity. The therophytic community displayed a limited range of functional traits, indicating mainly habitat filtering, but within this range, the evenness of the distribution indicated limiting similarity. On the younger island, the range of traits did not differ from random. However, within this range of traits, one therophytic community showed signs of limiting similarity, while the second therophytic community displayed uneven functional trait distribution, indicating mainly habitat filtering. The three indices reflected different facets of functional diversity and were not correlated, thus we may argue that they are not redundant, and we even detected different mechanisms of assembly within the same community. Conclusions The functional diversity of the therophytic communities in the younger island implied no specific assembly mechanism; perhaps due to its age, the community is still at the early stages of colonization (i.e. stochastic processes, such as arrival of new species, prevail). In the older island, the lack of disturbances for a long period allowed the establishment of communities assembled by specific mechanisms, such as competition and habitat filtering. [ABSTRACT FROM AUTHOR]

The universality of the shape of the species-area relationship (SAR) is subject to regular debate. Recently, Storch et al. (2012) argued that species-area relationships collapse into a single curve at continental scales after the axes are rescaled adjusting the area-axis being to the mean range size of species and the species-axis to the species richness of an area equal to mean range size. It has been claimed that this rescaling generates a universal model, invariant of taxon and continent, and that it is driven by differences in range sizes. Here, we test the universality of the rescaled SAR across scales smaller than the continental level, using presence data for plants, birds and butterflies. We also test an alternative rescaling approach, by using the total extent of the study area and total species richness. At the scales analysed here, we found that the proposed rescaling by Storch et al. adjusts for differences in the extent of the study area and for variation in gamma diversity. Consequently, while the rescaled curves were closely aligned, they did not converge into a single curve. The observed remaining variation is independent of scale and biogeographical region, and is correlated with beta diversity; thus, it reflects the differentiation of species composition in space. [ABSTRACT FROM AUTHOR]

Beta diversity provides a link between species diversity in a region to species diversity within sites. Many metrics have been proposed for its estimation each reflecting a different aspect of the phenomenon. Many of them are more informative of the variation in alpha diversity among samples and the sampling effort (number of sampling units) rather than of the species assemblage differentiation. Here, we propose an index based on the sampling effort needed to fulfil a certain criterion and accounts for the relationship between the initial slope of the species accumulation curve and mean alpha diversity., For defining the index, we consider a set of n samples with S( n) species among R( n) total occurrences. The shared species occurrences are I( n) = R( n) − S( n). The proposed new index ( N*) is defined as the point, in terms of n, where I( n) crosses S( n). Samples taken beyond that point ( N*) contribute, cumulatively, more to the shared occurrences rather than to new species. For the estimation of N*, we provide the R function 'Nstar' based on the specaccum function in the vegan package., We tested the properties of N* on simulated datasets with known community assembly patterns and on a dataset of plant diversity of Greek Natura 2000 protected areas., N* is not mathematically confounded with alpha or gamma diversity. It depends on the relationship between gamma and alpha (Whittaker's index) but, furthermore, it reflects the variation in species occupancies. Thus, if a number of random samples, sufficient for the reliable estimation of mean alpha diversity and the species accumulation curve, is collected, N* converges to a value that does not change by the inclusion of more samples from the same region. N* depends primarily on the proportion of new species expected in each next sample., N* declines with nestedness in community structure, while it increases with species turnover. This holds for plant diversity of Greek Natura 2000, where N* exhibited lower values in island compared to continental regions reflecting the increased nestedness of island communities. [ABSTRACT FROM AUTHOR]

1. Halting biodiversity loss, a major environmental challenge, relies on the understanding of species richness patterns. The assessment of species richness is often hampered by limited taxonomic knowledge and the general dearth of trained systematists. Research has shown that we can predict the number of species in a community by the number of higher order taxonomic units present. Here, we test whether we need to know all the genera, families or orders in order to do so. Further, the number of common species in a region is a good predictor of total richness and we test if this predictability translates to using higher taxa. 2. We used data from 240 sites from the Natura 2000 network of protected areas in Greece, including 5148 plant species and subspecies, which are grouped in 1113 genera 174 families and 56 orders. We correlated species richness with the number of common genera, families or orders present. The analysis was repeated using the number of the most speciose higher orders instead of the most common. 3. We found that we do not need to know all higher order taxa present, in order to predict species richness. If we know how many out of the 30 most common orders are present, we can reliably predict the number of species. Similar results were obtained if we know how many of the 60 most common families or 200 most common genera are present. 4. Equally good results were obtained using the same numbers of the most speciose higher orders. 5. Synthesis and applications. Our analysis demonstrates that species richness can be predicted from the number of common or more speciose genera, families and orders present. These predictions hold without complete sampling of these higher taxa. The implication is that we need only limited systematic knowledge, resources and effort in order to predict species richness. Assuming these findings hold in other taxonomic groups and in other regions, we argue that the uncertainty introduced by limited knowledge of the systematics ... [ABSTRACT FROM AUTHOR]

Aim To examine the way in which ‘area’ and ‘habitat diversity’ interact in shaping species richness and to find a simple and valid way to express this interaction. Location The Natura 2000 network of terrestrial protected areas in Greece, covering approximately 16% of the national territory. Methods We used the Natura 2000 framework, which provides a classification scheme for natural habitat types, to quantify habitat heterogeneity. We analysed data for the plant species composition in 16,143 quadrats in which 5044 species and subspecies of higher plants were recorded. We built a simple mathematical model that incorporates the effect of habitat diversity on the species–area relationship (SAR). Results Our analysis showed that habitat diversity was correlated with area. However, keeping habitat diversity constant, species richness was related to area; while keeping area constant, species richness was related to habitat diversity. Comparing the SAR of the 237 sites we found that the slope of the species–area curve was related to habitat diversity. Main conclusions Discussion of the causes of the SAR has often focused on the primacy of area per se versus habitat heterogeneity, even though the two mechanisms are not mutually exclusive and should be considered jointly. We find that increasing habitat diversity affects the SAR in different ways, but the dominant effect is to increase the slope of the SAR. While a full model fit typically includes a variety of terms involving both area and habitat richness, we find that the effect of habitat diversity can be reduced to a linear perturbation of the slope of the species accumulation curve. [ABSTRACT FROM AUTHOR]

We analysed the dynamics of a plant–pollinator interaction network of a scrub community surveyed over four consecutive years. Species composition within the annual networks showed high temporal variation. Temporal dynamics were also evident in the topology of the network, as interactions among plants and pollinators did not remain constant through time. This change involved both the number and the identity of interacting partners. Strikingly, few species and interactions were consistently present in all four annual plant–pollinator networks (53% of the plant species, 21% of the pollinator species and 4.9% of the interactions). The high turnover in species-to-species interactions was mainly the effect of species turnover ( c. 70% in pairwise comparisons among years), and less the effect of species flexibility to interact with new partners ( c. 30%). We conclude that specialization in plant–pollinator interactions might be highly overestimated when measured over short periods of time. This is because many plant or pollinator species appear as specialists in 1 year, but tend to be generalists or to interact with different partner species when observed in other years. The high temporal plasticity in species composition and interaction identity coupled with the low variation in network structure properties (e.g. degree centralization, connectance, nestedness, average distance and network diameter) imply (i) that tight and specialized coevolution might not be as important as previously suggested and (ii) that plant–pollinator interaction networks might be less prone to detrimental effects of disturbance than previously thought. We suggest that this may be due to the opportunistic nature of plant and animal species regarding the available partner resources they depend upon at any particular time. [ABSTRACT FROM AUTHOR]

Fire, a frequent disturbance in the Mediterranean, affects pollinator communities. We explored the response of major pollinator guilds to fire severity, across a fire‐severity gradient at different spatial scales. We show that the abundance of all pollinator groups responded to fire severity, and that bees and beetles showed in addition a significant species‐diversity response. Bees, sawflies, and wasps responded to fire severity at relatively small spatial scales (250–300 m), whereas flies and beetles responded at larger spatial scales. The response of bees, sawflies, and wasps was unimodal, as predicted by the intermediate disturbance hypothesis, whereas flies and beetles showed a negative response. A possible explanation is that the observed patterns (spatial scale and type of response) are driven by taxa‐specific ecological and life‐history traits, such as nesting preference and body size, as well as the availability of resources in the postfire landscape. Our observational study provides an insight into the effect of fire severity on pollinators. However, future research exploring the explicit link between the pre‐ and postfire landscape structure and pollinator traits and responses is required for further establishment and understanding of cause–effect relationships. [ABSTRACT FROM AUTHOR]