Nestedness Components Research Articles

Partitioning the effects of regional, spatial, and local variables on beta diversity of salt marsh arthropods in Chile.

AimWe examined the influence of regional, spatial, and local variables (edaphic characteristics and vegetation structure) on patterns of arthropod variation along the Chilean coast by partitioning beta diversity into its turnover and nestedness components.Location2,000 km along the coast of Chile.MethodsWe collected ground‐dwelling arthropod samples from nine marshes during two seasons. A clustering method was used to examine patterns of arthropod similarity across salt marshes. We also calculated multiple‐site beta diversity and partitioned it into its turnover and nestedness components. Variation partitioning was then used to identify the major drivers of their variation (regional, spatial, and local variables). We compared results for the whole arthropod community and for the most abundant, speciose, and functionally different groups, Crustacea, Coleoptera, and Araneae.ResultsSalt marsh arthropod similarities did not depend on the geographic proximity of sites. Arthropod beta diversity was mainly determined by its turnover component. A significant fraction of community variation was related to the spatially structured variation of climate or edaphic factors. However, the exclusive contribution of spatial variables had also a role.Main conclusionsEach salt marsh on the Chilean coast has the capacity to accommodate unique invertebrate taxa. Species sorting along the climatic gradient together with dispersal‐based processes seems the key structuring force of the arthropods and Crustacean variation in the marshes we studied, while species sorting alone might be more important for Coleoptera variation.

β‐diversity scaling patterns are consistent across metrics and taxa

β‐diversity (variation in community composition) is a fundamental component of biodiversity, with implications for macroecology, community ecology and conservation. However, its scaling properties are poorly understood. Here, we systematically assessed the spatial scaling of β‐diversity using 12 empirical large‐scale datasets including different taxonomic groups, by examining two conceptual types of β‐diversity and explicitly considering the turnover and nestedness components. We found highly consistent patterns across datasets. Multiple‐site β‐diversity (i.e. variation across multiple sites) scaling curves were remarkably consistent, with β‐diversity decreasing with sampled area according to a power law. For pairwise dissimilarities, the rates of increase of dissimilarity with geographic distance remained largely constant across scales, while grain size (or scale level) had a stronger effect on overall dissimilarity. In both analyses, turnover was the main contributor to β‐diversity, following total β‐diversity patterns closely, while the nestedness component was largely insensitive to scale changes. Our results highlight the importance of integrating both inter‐ and intraspecific aggregation patterns across spatial scales, which underpin substantial differences in community structure from local to regional scales.

Local rise of phylogenetic diversity due to invasions and extirpations leads to a regional phylogenetic homogenization of fish fauna from Chinese isolated plateau lakes

Human-mediated introductions of exotic species and extirpations of native species have modified the composition of biotic communities throughout the world, but the consequences of introductions and extirpations on local phylogenetic diversity (alpha-diversity) and on phylogenetic distinctiveness between sites (beta-diversity) remains poorly investigated. Here we analyze the long-term impacts of extirpations and invasions on both phylogenetic and taxonomic alpha and beta diversity of fish assemblages in Chinese isolated lakes. Data of fish assemblages in 15 lakes were grouped into three periods spanning the last 75 years: historical, intermediate and current periods. We partitioned phylogenetic beta diversity into turnover and nestedness component, and examined how introductions and extirpations led to temporal changes in alpha and beta diversity using linear regression and multiple regression models on distance matrices, respectively. Introductions and extirpations caused an increase of phylogenetic diversity (Δ+) and phylogenetic unevenness (Λ+) within the lakes, but the phylogenetic dissimilarity between lakes declined. Such trend, resulting from 60 years introductions and extirpations, was mainly due to a decline of the phylogenetic turnover, indicating that the replacement of native endemic species by widespread exotic species was the main driver of the observed phylogenetic homogenization. Temporal changes in phylogenetic and taxonomic dissimilarities were positively correlated, and taxonomic homogenization causes phylogenetic homogenization in ca. 60% of the lake pairs. Nevertheless, taxonomic homogenization turns to phylogenetic differentiation in one third of lake pairs due to the extirpation of the closely-related species and the introduction of distinct exotic species belonging to different lineages among lakes. Therefore, measuring phylogenetic diversity changes provides complementary information to taxonomy, and gives support to the Darwin’s naturalization hypothesis stipulating that species distantly related to natives easily establish in their introduction range. Our results demonstrate that half a century of anthropogenic disturbance was sufficient to blur the phylogenetic distinctiveness among lakes that resulted from the last 5 million years evolutionary history of the Yun-Gui plateau.

Environmental heterogeneity and dispersal limitation explain different aspects of β‐diversity in Neotropical fish assemblages

AbstractFrom a metacommunity perspective, patterns of β‐diversity emerge from the interplay between spatial and environmental processes. For obligate aquatic dispersers, river network constraints can be reflected in diversity patterns.Here, we aimed to determine the effects of environmental heterogeneity and spatial connectivity on β‐diversity components. We sampled fish assemblages in 21 sites across a longitudinal gradient. Beta‐diversity for taxonomic and functional composition among sites was decomposed into its turnover and nestedness components. We investigated whether environment was more important to functional β‐diversity and spatial factors had a higher contribution to dissimilarity in species composition. Further, we tested whether environmentally homogeneous sites with higher spatial connectivity showed lower compositional changes.We found that spatial factors were more important for taxonomic β‐diversity, whereas environment explained functional dissimilarity among habitats. Although environment and spatial factors contribute to total β‐diversity, they explained different components: while environment explained a higher portion of turnover, spatial factors were related to nestedness. The effects of mere spatial isolation and directional connectivity differed for species and functional β‐diversity and for the components of β‐diversity. Including directionality in spatial connectivity enabled the explanation of a higher proportion of variation of total species β‐diversity and its turnover.Our results suggest that niche and spatial processes may influence differently taxonomic and functional β‐diversity components. Thus, habitat filtering was the primary mechanism affecting functional diversity and species turnover, whereas spatial connectivity drove species nestedness.

Biogeographic Patterns among Seed-Bearing and Spore-Bearing Plants across the California Channel Islands

Spore-bearing and seed-bearing plants differ in their ability to colonize islands from mainland sources. To assess the importance of these differences, we investigated patterns of species richness and species composition for the native bryophyte, fern, and seed plant floras of the California Channel Islands. Native richness was regressed against island area, maximum elevation, distance to mainland, distance to nearest propagule source along prevailing wind trajectories, and latitude for the 3 plant groups. Ordinations, Mantel tests, randomization tests, and an analysis partitioning beta diversity into turnover and nestedness components were used to identify similarities and differences in species composition across the 3 groups. Patterns of species richness were mostly consistent across the 3 groups, with island area and maximum elevation being much more important than distance to mainland or distance from nearest propagule source. Patterns of species composition were also generally consistent across the 3 groups. The 3 floras exhibit similar patterns of compositional change across the archipelago and these patterns are not driven by geographic distance among islands. Island area and maximum elevation were significant predictors of compositional change, but the 2 distance metrics were not. The seed plant flora exhibited strong turnover between the 4 northern and 4 southern islands, while the bryophyte flora exhibited southern islands floras nested within those of northern islands. We interpret these findings as suggesting that ecological filtering is more important than dispersal limitation for developing both seed-bearing and spore-bearing plants on the islands.

Relating beta diversity of birds and butterflies in the Great Basin to spatial resolution, environmental variables and trait‐based groups

AbstractAimWe sought to characterize spatial and temporal beta diversity of birds and butterflies in the Great Basin (western U.S.A.) and to determine whether the magnitude of beta diversity was associated with spatial resolution, trait‐based groups or local environmental variables.LocationCentral and western Great Basin, western U.S.A.Time period1995–2014.Major taxa studiedBirds and butterflies.MethodsWe calculated temporal and spatial beta diversity of birds and butterflies at two spatial resolutions, points (birds) or transects (butterflies) and canyons (birds and butterflies). Points and transects corresponded to the spatial resolution of sampling, whereas canyons might be a more ecologically meaningful resolution. We partitioned beta diversity into turnover and nestedness components, and we calculated these components for entire assemblages and for trait‐based groups within assemblages. We used Bayesian hierarchical models to relate turnover and nestedness to spatial resolution, trait‐based groups and environmental variables.ResultsVariation in the composition of bird and butterfly assemblages was primarily associated with turnover. Species composition was more consistent at the resolution of canyons than at finer spatial resolutions. The species composition of birds changed more through space than through time, and spatial turnover of bird species tended to be higher than that of butterfly species. There were few strong associations of turnover and nestedness with environmental variables, and none with trait‐based groups.Main conclusionsOur results suggest that the identities of bird and butterfly species vary at locations within canyons among years but are less variable among canyons. Decreases in temporal turnover as spatial resolution increases suggest that, at fine spatial resolutions and among years, bird and butterfly species in the Great Basin might acquire resources somewhat opportunistically rather than via strong interspecific competition (birds and butterflies) or site tenacity to breeding territories (birds).

Polychaete diversity patterns along an environmental gradient in Términos Lagoon, a tropical lagoon-estuarine system in the southern Gulf of Mexico

In this study we analyze the faunal changes along 2 transects (5 stations each) across Terminos Lagoon. We also examined the role of the environmental gradients in controlling the number and composition of the polychaete species, and evaluated the spatial changes of beta-diversity. In total, 299 individuals from 51 species and 24 families were identified. Salinity was the most important factor to define the environmental gradients ( r2 > 0.83), but the variations in the number of species did not follow this spatial trend. The highest species richness was found in the eastern transect (mean: 12 spp./station, 78.0 ind./0.1 m2), while the western transect harbored a less diverse (mean: 6 spp./station) and less abundant fauna (mean: 21.67 ind./0.1 m2). A high similarity value (0.70) was found between the transects, but the distribution of each species was very irregular, which in turn caused a decrease in the similarity among stations at each transect (< 0.54). Except among the middle stations of the western transect, where the nestedness component represented all the beta-diversity value (βnes: 0.80 to 0.88), the species turnover (βsim: 0.38-1.0) was the dominant factor of the total dissimilarity among the polychaetes inhabiting Terminos Lagoon.

The role of habitat and daily activity patterns in explaining the diversity of mountain Neotropical dung beetle assemblages

AbstractThe interaction between land use and climate change is expected to strongly affect species distributions along high elevation landscapes. We aimed to test the effect of climatic variables on community metrics among five types of land use in a high elevation landscape. We described dung beetle spatial and temporal taxonomic and functional diversity patterns, and partitioned β‐diversity into turnover and nestedness components. The interaction between land use and daily period of activity mostly drives abundance, functional richness and functional diversity, but not dung beetle species richness. Unlike Neotropical lowlands, species richness and abundance in open environments are similar to those existing in forests. Temperature is an important predictor of abundance and functional divergence. There is a higher spatial component of the taxonomic β‐diversity, which is highly driven by species turnover. The temporal component of the taxonomic β‐diversity was strongly driven by nestedness, where night assemblages are sub‐sets, although not entirely, of diurnal assemblages. For functional diversity, the temporal β‐diversity was much higher than the spatial β‐diversity, but both were similarly represented by functional group turnover and nestedness. The composition of nocturnal and diurnal assemblages is clearly different, even more than the differences observed between habitats. However, taxonomic turnover is the dominant force between sampling sites while nestedness dominates the daily pattern. This means that forest habitats are unlikely to act as shelters for grassland species under a scenario of rising temperature.

How do bat, rodent, and marsupial communities respond to spatial and environmental gradients? Insights from a deconstruction of mammal beta diversity from the Atlantic Forest of South America.

Space and environment are fundamental in influencing the community structure. However, their relative influences vary according to species' biological characteristics. Here we test whether differences in life-history traits mainly linked to dispersal abilities influence bat, rodent and marsupial beta diversity along spatial and environmental gradients. We expect bat beta diversity to be weakly related with space in comparison to dispersal-limited rodents and marsupials. Using data from communities distributed along the Atlantic Forest of South America, we calculated the total beta diversity and its turnover and nestedness components for each group. We estimated the strength of correlation of beta diversity and its components along spatial and environmental gradients, comparing their importance within and between groups. Space had the higher influence on rodent and marsupial beta diversity. For bats, both gradients influenced similarly their community composition. Between taxa, the influence of these gradients did not differ for rodents and marsupials, while bats presented a stronger relationship with environment compared to non-volant small mammals. Also, all groups presented a similar influence of the spatial gradients on their community structure, despite their differences in dispersal abilities. Our results suggest that differences in biological characteristics partially influence the community structure of these mammals, with their responses along space likely reflecting similar biogeographical dynamics affecting their distribution. Overall, our results improve the understanding of the processes structuring these communities, highlighting the benefits of comparative analyses within a beta diversity perspective to better understand the influence of multiple processes on the community assembly along geographical gradients.

Geography, climate, ecology: What is more important in determining bee diversity in the Aegean Archipelago?

AbstractAimUnderstanding which factors drive α‐ and β‐diversity is fundamental to ecological and biogeographical research. Especially in archipelagos, diversity patterns are interesting due to the numerous factors influencing them. Here, we investigate the importance of climate and ecogeographical factors in shaping α‐ and β‐diversity patterns of bee species in the Aegean Archipelago, a bee diversity hotspot.LocationNineteen islands in the Aegean Archipelago, located along a N–S climate gradient.MethodsWe systematically sampled the bee fauna of phryganic communities in 100 sites across 19 islands. Using generalized linear models (GLMs), we tested climatic (viz. annual mean temperature and annual precipitation), geographical (island area, proportion of surrounding land mass, distance to climatically similar land mass, and maximum step length of pathway to nearest island/mainland), and ecological parameters (viz. floral abundance) as determinants of bee diversity. Following a multimodel island species–area relationship (ISAR) framework, we ranked islands according to the observed richness to identify biodiversity hotspots. Furthermore, we estimated the effect of the above factors on overall β‐diversity as well as on turnover and nestedness components, using multiple regression models on distance matrices.ResultsIsland area was the best predictor, positively affecting α‐diversity, together with precipitation, surrounding land mass proportion, and floral abundance. Temperature was found to have a significant negative effect on α‐diversity. Among all study islands, Samothraki and Kea stood out as bee diversity hotspots, with a bee richness higher than predicted by the multimodel ISAR. The overall β‐diversity was mainly driven by the turnover component and positively related to precipitation differences, whereas the nestedness component was positively affected by differences in area and surrounding land mass proportion.Main conclusionThis study highlights the importance of geography and climate in shaping both α‐ and β‐diversity of bees in the Aegean and suggests that both factors are likely to be crucial for analysing and predicting bee diversity responses to future environmental changes.

Back into the past: Resurveying random plots to track community changes in Italian coastal dunes

Resurveying studies are commonly appreciated as a means to monitoring temporal changes in plant diversity. However, most of them still rely on phytosociological plots, which, although representing an invaluable source of data, can lead to biased estimates of vegetation changes. At the community-level, temporal changes can be quantified by means of beta-diversity measures. However, compositional variation can be the result of two different, often contrasting, processes: turnover and nestedness. In this context we test the effectiveness of resurveying approaches based on quasi-permanent plots in revealing temporal changes in herbaceous communities of Mediterranean coastal dune systems. Indeed, due to their being highly dynamic, coastal dunes can be considered ideal habitats for implementing such tools. In particular, we quantified temporal changes in species composition occurred over 10–15 years by calculating Sørensen index of dissimilarity and, in order to determine whether the change was really driven by species turnover, we partitioned Sørensen index into its two components of turnover and nestedness. At the same time, since diagnostic species are considered to be particularly sensitive to habitat modifications and helpful in assessing changes in the ecological structure of a community, we analyzed temporal changes in the occurrence and cover of diagnostic species of the investigated habitats. Results show that coastal dune communities of our study area underwent consistent changes during the analyzed time-span. Almost 25% of the historical plots disappeared. Major transformations, mainly driven by species turnover, involved upper beach communities, embryonic and mobile dunes, as revealed by the parallel analysis of beta diversity and diagnostic species. This work shows how resurveying approaches can efficiently reveal useful insights on vegetation dynamics, therefore providing a solid basis for the implementation of effective conservation strategies, especially in endangered habitats.

The biogeography of non-marine molluscs in the Tuscan Archipelago reveals combined effects of current eco-geographical drivers and paleogeography

We investigated the role of present (Recent) and historical (Pleistocene, i.e., Wurmian Last Glacial Maximum) eco-geographical variables on the richness and diversity of non-marine molluscs in the Tuscan Archipelago, as well as inter-island faunal dissimilarity and relationships with source pools (Sardinia and Corsica, Tuscany). The association between species richness and present and historical eco-geographical variables were assessed with Spearman’s rank correlation test, while faunal dissimilarity both between islands and with their source pools was analyzed through beta-diversity partitioning (Sorensen index and its nestedness and turnover component) with UPGMA clustering tested with a multiscale bootstrap procedure. Non-metric multidimensional scaling in RGB color space was also used. Multiple regressions on distance matrices were then applied to explain assemblage composition between islands. Analyses were performed on all species and on all species except aliens. The overall framework showed the combined effects of current eco-geographical and paleogeographical imprints on non-marine malacofauna in the Tuscan Archipelago. However, excluding aliens, differences in species spatial turnover showed a clear correlation with Pleistocene inter-island distances, evidence of stronger historical biogeographical relationships between islands. This may indicate that widespread native species established their distribution during the Pleistocene, while alien species spread into the Tuscan Archipelago through stochastic and human-mediated dispersion events in recent times. Interestingly, Giglio’s relationships do not agree with the most accepted paleogeographical model, suggesting that this island might have been connected to the Tuscan mainland during the Wurmian Last Glacial Maximum. An in-depth revision of the paleogeographic framework of the northern Tyrrhenian is therefore called for.

Nestedness-resultant community disassembly process of extinction debt in a highly fragmented semi-natural grassland

There are two major processes of species disassembly after landscape changes: non-random loss of species resulting in nested assemblages and species replacement resulting in spatial species turnover. Although time-lagged responses of species to landscape change have been widely recognized, few studies have empirically evaluated which of these two processes is more closely related to extinction debt (i.e., postponed species extinction following habitat loss). This study aimed to understand the underlying processes of extinction debt by partitioning β-diversity into components of species nestedness and species turnover. We measured grassland species richness at three spatial extents in a highly fragmented semi-natural grassland landscape in Japan. Dissimilarity-based β-diversity was partitioned into two components (i.e., nestedness-resultant dissimilarity [βsne] and turnover-resultant dissimilarity [βsim]), which were further analyzed using principal coordinates analyses (PCoA). The relationships between the variability of PCoA axis 1 scores and the current and past habitat proportions were evaluated. A significant positive relationship between current grassland species richness and past (i.e., the 1910s) grassland proportion was found at the largest spatial extent. The first axis of PCoA based on βsne showed significant correlation with past habitat proportions, whereas the PCoA axis based on βsim showed no significant correlation with either the current or past habitat proportions. A non-random loss of grassland species represented by nestedness underlay the extinction debt found at the landscape level. There is a chance of predicting the loss of species from the nested ranks of species which likely reflects the gradient of species vulnerability to historical landscape changes.

Spatial but not temporal dung beetle β‐diversity components are scale‐dependent in a mainland–island scenario

Abstractβ‐diversity is key in understanding how ecological communities have been assembled across spatiotemporal scales. Separating β‐diversity into its process‐related components can provide richer insights into biodiversity organization. In this study, we aimed to investigate the spatial and temporal patterns of β‐diversity components in the composition and structure of dung beetle communities. Dung beetles were sampled in 20 Atlantic Forest sites in a mainland–island scenario. We partitioned β‐diversity dissimilarity based on species composition and abundance into turnover and nestedness components, and into balanced variation in abundance and abundance gradient components respectively. The mainland had higher multiple‐site values of spatial turnover and balanced variation in abundance than the island; meanwhile, nestedness‐resultant dissimilarity and abundance gradients had low relative importance, although the latter values were always higher on the island. There was an increase of spatial turnover and balanced variation in abundance with spatial extent, while nestedness‐resultant dissimilarity and abundance gradients were unrelated to the scale. The temporal turnover increased with increasing spatial extents and a different response pattern occurred between mainland and island. Our study provides support for how spatial extents influence both incidence‐based and abundance‐based β‐diversity components and shape metacommunity composition and structure in mainland–island systems.

Expected impacts of climate change threaten the anuran diversity in the Brazilian hotspots.

We performed Ecological Niche Models (ENMs) to generate climatically suitable areas for anurans in the Brazilian hotspots, the Atlantic Forest (AF), and Cerrado (CER), considering the baseline and future climate change scenarios, to evaluate the differences in the alpha and beta diversity metrics across time. We surveyed anuran occurrence records and generated ENMs for 350 and 155 species in the AF and CER. The final predictive maps for the baseline, 2050, and 2070 climate scenarios, based on an ensemble approach, were used to estimate the alpha (local species richness) and beta diversity metrics (local contribution to beta diversity index and its decomposition into replacement and nestedness components) in each ~50 × 50 km grid cell of the hotspots. Climate change is not expected to drastically change the distribution of the anuran richness gradients, but to negatively impact their whole extensions (i.e., cause species losses throughout the hotspots), except the northeastern CER that is expected to gain in species richness. Areas having high beta diversity are expected to decrease in northeastern CER, whereas an increase is expected in southeastern/southwestern CER under climate change. High beta diversity areas are expected to remain in the same AF locations as the prediction of the baseline climate, but the predominance of species loss under climate change is expected to increase the nestedness component in the hotspot. These results suggest that the lack of similar climatically suitable areas for most species will be the main challenge that species will face in the future. Finally, the application of the present framework to a wide range of taxa is an important step for the conservation of threatened biomes.

Beta Diversity Patterns of Post-fire Forests in Central Yunnan Plateau, Southwest China: Disturbances Intensify the Priority Effect in the Community Assembly.

Post-fire succession is an ideal case for studying effects of disturbance on community assembly, and the key is to disentangle the contributions of assembly processes to the variation of community composition, namely beta diversity, and the contingent scales. The central Yunnan Plateau of Southwest China is characterized by monsoon related seasonal drought, and frequent forest fires. We sampled five fire sites burned in different years and a middle aged forest, measured species composition dissimilarity and its species turnover and nestedness components, within each fire site and across all sites. Results indicated species turnover as the primary component of beta diversity within all communities. There was no trend of change with year-since-fire (YSF) in beta diversity among early post-fire communities, but beta diversity in the middle aged community was significantly higher. Species turnover patterns across fire sites revealed a weak dispersal limit effect, which was stronger at lower than upper slope position for woody plants, and reverse for herbs. At the site scale, the species dissimilarity and turnover both enlarged with increasing slope position difference, especially in the middle-aged community, but the species nestedness had no consistent trend among sites, except a decreasing trend in the middle-aged forest. (Partial) Mantel tests indicated habitat filtering [primarily indicating total nitrogen (TN) and slope position] played a much stronger role than dispersal limit and YSF (indicating competition intensity) for the post-fire forest assembly at the landscape scale, for both woody and herbaceous layers. However, at the site scale, Mantel tests indicated a diminishing effect of soil nutrient filtering with increasing YSF, while effects of topography and spatial distance in the middle aged community was stronger. This divergence suggests the primary assembly mechanism gradually shift away from the soil constraint. While the seasonal drought and the mountain topography dominate the environmental legacy, our results imply that fires may reinforce a priority effect in the forests assembly in this region, by creating a habitat filtering (e.g., moisture and nitrogen limitation) effect on species composition in post-fire communities.

Is β‐diversity of Amazonian ant and dung beetles communities elevated at rainforest edges?

AbstractAimThousands of kilometres of rainforest edges are created every year through forest fragmentation, but we have little knowledge of the impacts of edges on spatial patterns of species turnover and nestedness components of β‐diversity.LocationA quasi‐experimental landscape in the north‐east Brazilian Amazon.MethodsWe sampled dung beetles and ants using a sampling design based on a fractal series of equilateral triangles that naturally allows examination at multiple spatial scales. We sampled two edge types (primary‐secondary and primary‐Eucalyptus forest) and three control sites immersed in primary, secondary and Eucalyptus forest. We measured β‐diversity between communities across the primary forest‐matrix edge and within communities at up to 1 km from the forest edge. We examined β‐diversity at multiple scales by partitioning the dissimilarity matrix into fractal orders representing inter‐point distances of ~32, ~100, ~316 and ~1,000 m and into turnover and nestedness components.ResultsTurnover but not nestedness was greater across the primary‐Eucalyptus forest than primary‐secondary forest edge. There was spillover of species across edges in both directions. Across edges and within controls, turnover was the main driver of β‐diversity. Within community, β‐diversity was increased for dung beetles at large scales (~300–1,000 m) at both edge types. This increase, however, was driven by elevated nestedness. Levels of β‐diversity were affected even ~300 m into habitat interiors, but appeared to be at control levels by 1 km.Main conclusionsThe effects of edges on the spatial dynamics of community composition penetrated far beyond the typical distances at which forest structure and microclimate are altered. This indicates that for a significant proportion of Amazonian communities, the underlying processes determining diversity may be impacted by deforestation.

Disentangling the correlates of species and site contributions to beta diversity in dung beetle assemblages

AbstractAimWe aimed to test whether contributions of individual species (SCBD) and contributions of single sites (LCBD) to overall beta diversity can be predicted by species metrics and species characteristics and also by community metrics and ecological variables, respectively.LocationA mainland‐island landscape in the southern Brazilian Atlantic Forest domain.MethodsDung beetles were sampled along 100 sampling units within four large forest fragments. We partitioned beta diversity into SCBD and LCBD aiming to explore their relationships to species and site characteristics, respectively. We then used a combination of multivariate methods and beta regression analyses to examine patterns in SCBD and LCBD. The occupancy, total abundance, niche position, niche breadth and biological traits of species were used as predictor variables for SCBD values. Community metrics, environmental and spatial variables, and temporal patterns in the beta diversity components of turnover and nestedness were used as predictor variables for LCDB values.ResultsWe found that SCBD was strongly related to various species characteristics, such as occupancy, abundance and niche position, but was not related to biological traits of species and niche breadth. In particular, occupancy and its quadratic term showed a very strong unimodal relationship with SCBD, suggesting that intermediate species in terms of site occupancy contribute most to beta diversity. LCBD was mostly explained by variation in species richness, with a negative relationship being detected. Litter height and large‐scale spatial variables were also important in explaining variation in LCBD.Main conclusionsSCBD and LCBD were highly predictably related to species occupancy and species richness, respectively. Environmental conditions and large‐scale spatial variables also correlated with LCBD values. Understanding the determinants of SCBD and LCBD may thus hold a key to various general ecological, bioassessment and conservation issues. Protecting sites with high LCBD values may be a suitable approach to practical biodiversity conservation.

Partitioning tadpole beta diversity in highland ponds with different hydroperiods

Pond hydroperiod and other aspects of environmental heterogeneity play important roles in metacommunity organization in freshwater systems. We examined tadpole species richness and dissimilarities among assemblages at different hydroperiods (3, 7, and 13 mo) in highland ponds in the Araucaria moist forest ecoregion of southern Brazil. We also investigated whether β diversity components changed in accordance with spatial and environmental factors. We sampled tadpoles at 18 ponds between September 2012 and April 2013. Tadpole species richness was lower in permanent than in temporary ponds, but pond hydroperiod was not associated with tadpole abundance and species dissimilarities. β diversity was almost completely caused by species replacement associated with pond area, presence of predatory fish, and type of margin. Despite its small contribution, the nestedness component was associated with water depth and geographic patterns. Our study suggests that tadpole communities in the highlands of Araucaria moist forests are niche structured.

Effects of dams decrease zooplankton functional β‐diversity in river‐associated lakes

Abstract In river–floodplain systems, the construction of dams causes environmental changes in the natural dynamics of rivers and the associated wetlands, which can affect both the taxonomic and functional composition of communities, and, consequently, ecosystem functioning. We evaluated zooplankton taxonomic and functional β‐diversity in sets of lakes associated with a preserved and a dammed river in a Neotropical floodplain. We expected that both β‐diversity measures would be lower in lakes associated with a dammed river than in lakes associated with a preserved river. β‐Diversity was partitioned into turnover and nestedness components, through multiple‐site dissimilarity measures, and compared with expected null models. We expected that nestedness would be more important for both the β‐diversity measures in lakes associated with the dammed river, whereas species and trait turnover would be more important in lakes associated with the preserved river. Functional β‐diversity was higher among lakes of the preserved river than of the dammed river, while taxonomic β‐diversity was not different between the rivers. Contributions of turnover and nestedness components were similar in the preserved river, whereas that of nestedness was higher in the dammed river, revealing the loss of extreme trait combinations from the functional space. Comparisons between observed and expected β‐diversity revealed a higher trait turnover than would be expected by species turnover in the preserved river, and no differences from the null models were observed in lakes associated with the dammed river. Our results suggest that dissimilarity in trait composition is influenced more by environmental changes associated with river damming than by dissimilarity in species composition such that a functional homogenisation occurs without a change in taxonomic β‐diversity. We propose the maintenance of preserved tributaries in floodplains, which sustain environmental heterogeneity, primarily if the nearby environments are already dammed. Furthermore, we reinforce the necessity of a pluralistic approach, considering both taxonomic and functional aspects of biodiversity in ecosystem management.