Nestedness Components Research Articles

Linking beta diversity patterns to protected areas: lessons from the Brazilian Atlantic Rainforest

Understanding the processes that drive patterns of beta diversity is crucial for planning conservation policies and for designing networks of protected area (PAs). Beta diversity can be decomposed into two components: 1—species turnover, the replacement of species by others resulting in a low proportion of shared species; 2—species nestedness—the result of differences in species richness, when a poorer community is a subset of species from a richer community. We aimed to evaluate beta diversity patterns and how they are represented in the network of PAs in southern Brazilian, regarding three forest types: Atlantic Forest s.s., Araucaria Forest, and Seasonal Forest. Beta diversity was partitioned into the turnover and nestedness components. Additionally, we examined spatial patterns of site similarity using distance decay curves. Beta diversity was mainly caused by species turnover (approx. 86%), with only a small contribution of nestedness (approx. 5%) in all three forests types. The patterns of distance decay curves revealed that even at small distances (50–100 km), we found a considerable decrease in similarities, reinforcing turnover patterns. As turnover brought the larger contribution to beta diversity, additional conservation efforts must target an increase in the number of PAs, that should be spread across each one of the regions, to maximize the protection of species diversity. Most of the PAs are currently limited to the eastern region and prioritize the Atlantic Forest s.s. Thus Araucaria Forest and Seasonal Forest should deserve special priority in new conservation actions, as they also contain high levels of species turnover.

Fine spatial grain, large spatial extent and biogeography of macrophyte‐associated cladoceran communities across Neotropical floodplains

Summary Metacommunity structure may be strongly influenced by spatial dynamics and environmental factors, as well as biogeographic effects. Here, we examined variation in lake cladoceran communities associated with floating macrophytes in the four major Brazilian floodplain systems (Amazônia, Araguaia, Pantanal and Paraná) in relation to local environmental factors, spatial components, climate variables and basin identity. Moran's eigenvector maps were used as a proxy to examine spatial structures within each drainage basin. The final sets of local environmental, climate and spatial variables were selected for constrained ordination models, using a forward selection method. We used variation partitioning to decompose variation in cladoceran community composition in relation to the four sets of predictor variables. Beta‐diversity indices were calculated to quantify the contributions of turnover and nestedness components to total beta diversity of cladocerans within each basin and across the basins. Variation partitioning showed that the pure fractions were relatively small, ranging from around zero for spatial and basin identity variables to 2% for climate variables and 4% for local environmental variables. The shared effect of local environmental, climate and basin identity was considerable, accounting for 17% of the total variance. Furthermore, the shared effect of climate and basin identity was also considerable (6%). In total, 32% of variation in cladoceran community structure could be explained by our predictor variables. Cladoceran metacommunities showed high levels of beta diversity attributed to the turnover component, within each floodplain and across all four floodplains. Our finding showed that species sorting was likely to be the main agent structuring cladoceran communities. Spatial processes were not important at very large spatial scales, contrary to what has been found in previous studies. This finding was most likely due to the inclusion of climatic variables in our analysis, combined with the high dispersal ability of cladocerans.

Effects of dispersal and environmental heterogeneity on the replacement and nestedness components of β-diversity.

Traditionally metacommunity studies have quantified the relative importance of dispersal and environmental processes on observed β-diversity. Separating β-diversity into its replacement and nestedness components and linking such patterns to metacommunity drivers can provide richer insights into biodiversity organization across spatial scales. It is often very difficult to measure actual dispersal rates in the field and to define the boundaries of natural metacommunities. To overcome those limitations, we revisited an experimental metacommunity dataset to test the independent and interacting effects of environmental heterogeneity and dispersal on each component of β-diversity. We show that the balance between the replacement and nestedness components of β-diversity resulting from eutrophication changes completely depending on dispersal rates. Nutrient enrichment negatively affected local zooplankton diversity and generated a pattern of β-diversity derived from nestedness in unconnected, environmentally heterogeneous landscapes. Increasing dispersal erased the pattern of nestedness, whereas the replacement component gained importance. In environmentally homogeneous metacommunities, dispersal limitation created community dissimilarity via species replacement whereas the nestedness component remained low and unchanged across dispersal levels. Our study provides novel insights into how environmental heterogeneity and dispersal interact and shape metacommunity structure.

Temporal variation in phytoplankton beta diversity patterns and metacommunity structures across subtropical reservoirs

Summary Analysing the beta diversity components and spatial patterns of species distribution may provide key insights into how local communities respond to human‐induced environmental changes. Indeed, analysing temporal variation in spatial patterns of species distribution may reveal trends of biotic homogenisation and its likely causes. We used an eight‐year phytoplankton data set generated from to 17 reservoirs in Brazil to analyse the temporal variability in beta diversity and its turnover and nestedness components. This data set was also used to determine metacommunity structures across these subtropical reservoirs. We tested whether there was any long‐term temporal trend in beta diversity that might be indicative of biotic homogenisation or differentiation. We also tested how temporal variation was related to climatic conditions, environmental heterogeneity, productivity and cyanobacterial dominance. Lastly, we verified whether the phytoplankton metacommunity showed non‐random structure. We did not find supporting evidence for biotic homogenisation among the reservoirs. Rather, we did find that nestedness decreased during the study. Environmental heterogeneity was the main variable positively related to phytoplankton beta diversity, while high ammonium concentration and cyanobacterial abundance were negatively correlated with spatial variation among the reservoirs. Despite the noticeable temporal variation in metacommunity structures, the phytoplankton species responded similar to latent environmental gradients. Clementsian patterns found mainly in fall and winter were consistent with differences in species composition between sites, reinforcing the role of environmental filtering in driving changes in these metacommunities. Our results suggest that eutrophication control is essential to prevent biotic homogenisation, at least in our study system. We also highlight that metacommunity patterns detected in snapshot surveys should not be extrapolated temporally.

象山港浮游动物β多样性及其成分变化的环境因子解释

PDF HTML阅读 XML下载 导出引用 引用提醒 象山港浮游动物β多样性及其成分变化的环境因子解释 DOI: 10.5846/stxb201606061083 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 海洋公益性行业科研专项（201105009-3）；国家科技支撑项目（2011BAD13B08）；浙江省自然科学基金（Y5080274，Y5100369）；宁波大学水产养殖浙江省重中之重一级学科开放基金资助（421500052） Interpretation of environmental factors affecting zooplanktonic beta diversity and its components in Xiangshan Bay Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:根据象山港24个站位浮游动物样品和配套环境数据，采用R语言的gdm工具包对浮游动物β多样性进行了广义非相似性模型（GDM）分析，并利用betapart工具包对β多样性进行了成分（周转和嵌套性）分解，探讨了环境因子与浮游动物β多样性及其成分间的关系。GDM模型分析结果表明，有10个环境变量（表层水温、溶解氧、水深、透明度、pH、叶绿素a、地理距离、电导率、盐度、悬浮颗粒物）对浮游动物β多样性有影响，解释了GDM模型偏差比例的75.2%。在这10个变量中，水温、溶解氧、水深是驱动β多样性变化重要因子，3个变量累计相对贡献比例占63.9%（以GDM模型偏差的可解释比例作为100%），其他7个变量占36.1%；3个变量中，又以水温最重要，相对贡献比例占到38.4%。从各预测变量的影响梯度看，地理距离、pH和盐度分别在约高于25 km、7.8和25，水温、叶绿素a含量分别在约低于22℃和0.5 μg/L时，随着变量梯度的增加，β多样性增大；而溶解氧、电导率、透明度和水深则随着梯度增加β多样性一直增加，悬浮颗粒物含量对β多样性几乎无影响。据β多样性成分分解结果，象山港浮游动物在时空变化上总体以周转为主，嵌套性很低。在象山港，浮游动物嵌套性主要发生于大型浮游动物和幼体类群，尤其是幼体类群，嵌套性在时空上几乎都高于周转。进一步的Pearson相关性分析表明，与大型浮游动物嵌套性显著相关的环境因子是水温和溶解氧，而与幼体类嵌套性显著相关的环境因子除水温和溶解氧外，还有电导率和流速。 Abstract:To explore the relationships between environmental factors and zooplanktonic beta diversity-and its component changes-zooplankton samples and corresponding environmental data were collected from 24 stations in Xiangshan Bay. Zooplanktonic beta diversity was analyzed by a generalized dissimilarity model (GDM) with the gdm package in the R language, and was further separated into two components-turnover and nestedness-using the betapart package. Analytical results with GDM showed that 10 environmental variables (surface water temperature, dissolved oxygen, water depth, transparency, pH, chlorophyll a, geographical distance, conductivity, salinity, and suspended particulate matter) affected zooplanktonic beta diversity and could explain 75.2% of the GDM deviation. Among the 10 variables, water temperature, dissolved oxygen, and water depth were the important driving factors for beta diversity changes, which explained 63.9% of the cumulative relative contribution (taking the interpretable proportion of the GDM deviation as 100%), while the other 7 factors accounted for 36.1%. Furthermore, water temperature was the most important driving factor among these three factors, which accounted for 38.4% of the cumulative relative contribution. According to the gradient effects of predictors, beta diversity increased with the increasing gradients of factors when the geographical distance, pH, salinity, water temperature, and chlorophyll a were above ca. 25 km, 7.8, 25, and under 22℃ and 0.5 μg/L respectively. Moreover, zooplanktonic beta diversity always increased with increasing dissolved oxygen, conductivity, transparency, and water depth. However, no obvious effect was found with the content change of suspended particulate matter. According to the results of partitioning beta diversity into turnover and nestedness components, turnover played a dominant role in the spatiotemporal changes of zooplankton, while the nestedness had small effects in Xiangshan Bay. Furthermore, the nestedness mainly occurred in the groups of macro-zooplankton and lava, especially in the latter group, and the spatiotemporal nestedness was almost always higher than turnover in the two groups. Further analyses of Pearson's correlation demonstrated that the water temperature and dissolved oxygen were significantly correlated with the nestedness of macro-zooplankton, and that the water temperature, dissolved oxygen, and two other factors-conductivity and velocity-were significantly associated with the nestedness in the lava group. 参考文献 相似文献 引证文献

Partitioning beta‐diversity through different pond hydroperiod lengths reveals predominance of nestedness in assemblages of immature odonates

AbstractPatterns of freshwater invertebrate assemblage structure in the transition from permanent to non‐permanent lentic habitats are well described in the literature. However, the effects of small changes in the hydroperiod of non‐permanent ponds on invertebrate assemblage structure remain less studied, especially on β‐diversity. Thus, we tested the effects of different pond hydroperiod lengths on the assemblage structure of immature odonates, in terms of both α‐ and β‐diversity. Small high‐altitude ponds with different hydroperiod lengths (assigned to ‘short’, ‘medium’ and ‘long’ hydroperiods) were sampled in southern Brazil between 2013 and 2014. Based on the hypothesis that shorter hydroperiods filter constituents of lentic fauna, i.e. that long‐living species cannot inhabit shorter‐hydroperiod ponds, we expected to find higher α‐ and β‐diversity in longer hydroperiods, as well as predominance of the nestedness component in β‐diversity. Restricted occurrence of some genera and higher α‐diversity of immature odonate assemblages was detected in long‐hydroperiod ponds. Within‐hydroperiod β‐diversity values did not vary among hydroperiods, because the occasional occurrence of some genera with high dispersal ability of adults in short‐hydroperiod ponds yielded similar values of the β‐diversity among hydroperiods. Partitioning of β‐diversity among hydroperiods revealed a significant higher contribution of the nestedness component rather than turnover. This pattern is explained by the occurrence of some generalist genera across the whole gradient of hydroperiod, as a subset of fauna in longer‐hydroperiod ponds. Thus, our results suggest that reduction in hydroperiod length, if occurring in the future climate change, would favor habitat‐generalist taxa in lentic ecosystems.

Metacommunity ecology meets biogeography: effects of geographical region, spatial dynamics and environmental filtering on community structure in aquatic organisms.

Metacommunity patterns and underlying processes in aquatic organisms have typically been studied within a drainage basin. We examined variation in the composition of six freshwater organismal groups across various drainage basins in Finland. We first modelled spatial structures within each drainage basin using Moran eigenvector maps. Second, we partitioned variation in community structure among three groups of predictors using constrained ordination: (1) local environmental variables, (2) spatial variables, and (3) dummy variable drainage basin identity. Third, we examined turnover and nestedness components of multiple-site beta diversity, and tested the best fit patterns of our datasets using the "elements of metacommunity structure" analysis. Our results showed that basin identity and local environmental variables were significant predictors of community structure, whereas within-basin spatial effects were typically negligible. In half of the organismal groups (diatoms, bryophytes, zooplankton), basin identity was a slightly better predictor of community structure than local environmental variables, whereas the opposite was true for the remaining three organismal groups (insects, macrophytes, fish). Both pure basin and local environmental fractions were, however, significant after accounting for the effects of the other predictor variable sets. All organismal groups exhibited high levels of beta diversity, which was mostly attributable to the turnover component. Our results showed consistent Clementsian-type metacommunity structures, suggesting that subgroups of species responded similarly to environmental factors or drainage basin limits. We conclude that aquatic communities across large scales are mostly determined by environmental and basin effects, which leads to high beta diversity and prevalence of Clementsian community types.

Tropical bryophyte floras: a homogeneous assemblage of highly mobile species? Insights from their spatial patterns of beta diversity

The impact of Pleistocene climate changes substantially varied between tropical regions, resulting in striking differences in angiosperm species richness caused by post-glacial recolonization delays. Tropical bryophytes, which have been perceived as extremely good dispersers due to biased rates of monoecy and hence spore production, differ strikingly from angiosperms in their similar patterns of species richness among tropical regions. Here, we analyse the patterns of beta diversity of tropical bryophytes to determine whether their high dispersal capacities have balanced patterns of species richness and erased any difference of post-glacial recolonization patterns between tropical regions. The partitioning of beta diversity for 7485 tropical moss species among 164 operational geographical units (OGUs) and 3276 liverwort and hornwort species in 154 OGUs revealed a slight, but significantly higher beta diversity among than within tropical regions. The nestedness component of beta diversity did not significantly differ between tropical regions. This indicates that, although regional migration rates were sufficient to erase differences of the impact of Pleistocene climate changes between tropical regions, the similar bryophyte species richness of tropical regions cannot be interpreted in terms of unrestricted migrations and that oceans act as a barrier to routine dispersal, which is sufficient to shape large-scale floristic patterns.

Tropical Estuarine Macrobenthic Communities Are Structured by Turnover Rather than Nestedness.

Turnover (i.e., species substitution) and nestedness (i.e., subsets of species from more diverse locations), the two main mechanisms used to explain the beta diversity of biological communities, have different implications for biodiversity conservation. To better understand how these mechanisms contribute to beta diversity, we tested the following hypotheses: (i) greater dissimilarity in community composition occurs between estuarine zones than other hierarchical level studied; (ii) beta diversity in these communities develops by turnover in estuaries with a lower degree of anthropogenic impact, but by nestedness in estuaries with a greater degree of anthropogenic impact; and (iii) the structuring mechanism is independent of season. We studied two tropical estuaries (dry and wet seasons) that vary in terms of land-use of the drainage basins. Subtidal benthic macroinvertebrates were sampled along the estuarine gradient in each of the two estuaries. The additive partitioning approach to species diversity was used to determine the hierarchical scale with the greatest dissimilarity in community composition. General beta diversity was measured using the Sorensen dissimilarity index, partitioning the turnover and nestedness components. The greatest dissimilarity in the composition of the communities occurred between the zones along the estuarine gradient in both seasons (dry = 58.6%; wet = 46.3%). In the estuary with a lower degree of anthropogenic influence, benthic macroinvertebrate diversity was generated by turnover regardless of the season. In the estuary with a greater degree of anthropogenic impact, beta diversity was structured by turnover during the dry season and a combination of both mechanisms during the wet season. We conclude that turnover is the principal mechanism responsible for beta diversity in benthic macroinvertebrate communities in tropical estuaries.

Nestedness and species replacement along bathymetric gradients in the deep sea reflect productivity: a test with polychaete assemblages in the oligotrophic north‐west Gulf of Mexico

AbstractAimTo test the hypothesis that low productivity drives the nestedness component of β‐diversity in polychaetes at the deep‐sea floor.LocationWestern Gulf of Mexico.MethodsWe used A. Baselga's (2010, Global Ecology and Biogeography, 19, 134–143) metrics of species replacement and nestedness to assess their overall significance with differences in depth and particulate organic carbon (POC) flux to the seafloor. We used M. A. Rodríguez‐Gironés & L. Santamaría's (2006, Journal of Biogeography, 33, 924–935) BINMATNEST to calculate the significance and direction of nestedness with depth and POC flux.ResultsNestedness was the most significant part of β‐diversity with depth and POC flux. The rank order of nestedness increased significantly with increasing depth, and decreased significantly with increasing POC flux. There was little endemism below 2000 m.Main conclusionThe polychaete fauna in the deepest western Gulf of Mexico is largely a nested subset of the shallower upper to mid‐bathyal fauna. While the causes of β‐diversity in the deep sea are undoubtedly multivariate, the relative importance of turnover and nestedness appears to be modulated by productivity in the form of POC flux to the seafloor. Under circumstances of extremely low POC flux and animal density in the deepest reaches of the Gulf, nestedness may be caused by some populations being maintained by immigration from larger populations upslope, or by biogeographic filtering for tolerance to abyssal conditions. Resources at great depths in regions of exceptionally low productivity may be too limited to permit adaptation resulting in endemism and continued downslope turnover. If productivity helps to explain the nestedness part of β‐diversity, this may lead to a more unified theory of deep‐sea biodiversity.

Riverine networks constrain β‐diversity patterns among fish assemblages in a large Neotropical river

Summary Riverine metacommunities have been studied mainly in streams and headwaters, and little is known about how dendritic networks affect metacommunity structure in large river systems. We, therefore, examined fish assemblages in the Upper Tocantins River, Amazon Basin, to investigate the hypothesis that riverine networks constrain metacommunity structure. In particular, we investigated (i) taxonomic and functional β‐diversity along the river channel (main stem) and major tributaries (branches); (ii) the relative importance of the turnover and nestedness components; and (iii) the relationship between β‐diversity and spatial structure (the distance decay of similarity). Fish assemblages were sampled over a year (2007–2008) at 17 sites distributed along the main stem (n = 8) and branches (n = 9). We recorded 170 fish species in the 100‐km river section studied. Local species richness ranged from 45 to 79, with higher mean values in the main stem; local assemblages, however, showed high functional richness, with no significant difference between the main stem and branches. We observed that the turnover component contributed 87.7% of the variation in taxonomic β‐diversity (Jaccard), while the nestedness‐resultant contributed 12.3%. Taxonomic β‐diversity was on average 2.5 times higher than functional diversity, and taxonomic turnover was on average four times greater than functional turnover. In addition, a null model showed that observed values of functional β‐diversity were not different from random expectations, given the observed level of taxonomic β‐diversity. Branches showed higher species turnover, while significant distance decay of similarity was observed only along the main stem. Functional β‐diversity was not different between the main stem and branches and did not correlate with watercourse distance. Our study revealed that fish metacommunity in this large river shows species turnover, but with high functional similarity. In addition, different β‐diversity patterns between the main stem and branches indicate that the dendritic network constrained metacommunity structure. Mass effects and dispersal limitations probably explain β‐diversity patterns in the main stem, while a combination of mechanisms (i.e., disturbance, specific biological functions and dispersal constraints) affect diversity in the branches.

Meiofauna communities, nematode diversity and C degradation rates in seagrass (Posidonia oceanica L.) and unvegetated sediments invaded by the algae Caulerpa cylindracea (Sonder)

We investigated meiofauna and sedimentary C cycling in seagrass (Posidonia oceanica) and unvegetated sediments invaded and not invaded by the non-indigenous tropical algae Caulerpa cylindracea. In both habitats, invaded sediments were characterized by higher organic matter contents. No effect was observed for prokaryotes and C degradation rates. In seagrass sediments, C turnover in invaded beds was about half that in not invaded ones. Meiofaunal communities varied significantly among invaded and not invaded grounds only in bare sediments. In both habitats, nematode species richness and assemblage composition were not affected by the algae. The effect of C. cylindracea on the turnover and nestedness components of the Jaccard dissimilarity varied between the two habitats. We show that the presence of C. cylindracea gives rise to variable consequences on meiofauna biodiversity and C cycling in different habitats. We conclude that further studies across different habitats and ecological components are needed to ultimately understand and predict the consequences of C. cylindracea invasion in shallow Mediterranean ecosystems.

Validating the use of unique trait combinations for measuring multivariate functional richness

Summary Quantifying functional trait diversity has provided important new insights for understanding ecosystem processes and functioning. Functional diversity is often partitioned into three components richness, evenness and divergence. Currently, a convex hull is used as a measure of multivariate richness, but this approach has some serious limitations. Consequently, we propose using the number of unique trait combinations (UTCs) as an approach to measure the filled trait space (the hypervolume containing all possible trait combinations) and propose a new index, sUTC, as the amount of filled trait space divided by the trait space range. Like convex hull approaches, UTC can be partitioned into alpha and beta components when used across sites, and the beta component can be further partitioned into turnover and nestedness components. Unlike convex hull approaches, UTC can be used more intuitively with existing diversity measures as it can be used in conjunction with abundance information. We present the concepts these indices are based on and give examples of their use. The new index, sUTC, is compared to the existing indices on the basis of criteria specified in the literature and one novel criterion. We test and evaluate the approach using simulated data and field data. We found that the UTC approach provided a more accurate assessment of functional richness than did the existing indices. The UTC approach is a multivariate approach to measuring functional richness that can accommodate continuous and categorical traits and can account for holes in the trait space.

Multiscale partitioning of small mammal β‐diversity provides novel insights into the Quaternary faunal history of Qinghai–Tibetan Plateau and Hengduan Mountains

AbstractAimTo assess the validity of four hypothesized drivers (Quaternary climate, niche conservatism, contemporary climate, spatial configuration) of small mammal beta diversity in the Qinghai–Tibetan Plateau (QTP) and the Hengduan Mountains (HDM).LocationQTP and HDM of China.MethodsWe partitioned the beta diversity of small mammals in QTP and HDM into the spatial turnover and nestedness components at the regional (longitudinal/latitudinal zones) and grid (1° × 1°) scales. Regional beta diversity was evaluated by calculating the multiple‐site dissimilarities and the distance‐dissimilarity relationships. We examined the relative effects of geographical distance, environmental difference, habitat diversity, geographical isolation and Quaternary climate stability on the beta diversity patterns.ResultsThe overall beta diversity in all longitudinal/latitudinal zones of both regions was primarily driven by spatial turnover, longitudinal nestedness patterns were almost non‐existent in QTP. Turnover was stronger in the latitudinal direction of QTP and in the longitudinal direction of HDM, which corresponded to the general topography of each region. At the grid scale, higher turnover was primarily concentrated in mountainous areas. Turnover was highly correlated with geographical distance and environmental difference in both regions, and geographical isolation was another strong predictor of turnover in HDM. Habitat diversity independently explained most of the variation in nestedness of HDM.Main conclusionsSpatial turnover is the primary cause of the small mammal beta diversity in QTP and HDM. Three non‐exclusive mechanisms including the historic effect of past glaciation, contemporary climate and spatial configuration of the landscape might act in combination to shape the beta diversity patterns in QTP and HDM, particularly the directional patterns. Our results challenge the prevailing view that the current distribution of QTP fauna is primarily explained by westward post‐glacial recolonization, and support the alternative idea that QTP retained considerable refugia and even centres of origin during the Quaternary glaciations.

Human-Induced Landscape Changes Homogenize Atlantic Forest Bird Assemblages through Nested Species Loss.

The increasing number of quantitative assessments of homogenization using citizen science data is particularly important in the Neotropics, given its high biodiversity and ecological peculiarity, and whose communities may react differently to landscape changes. We looked for evidence of taxonomic homogenization in terrestrial birds by investigating patterns of beta diversity along a gradient of human-altered landscapes (HAL), trying to identify species associated with this process. We analyzed bird data from 87 sites sampled in a citizen science program in the south Brazilian Atlantic Forest. Regional-scale taxonomic homogenization was assessed by comparing beta diversity among sites in different HALs (natural, rural or urban landscapes) accounting for variation derived from geographical distance and zoogeographical affinities by georeferencing sites and determining their position in a phytogeographical domain. Beta diversity was calculated by multivariate dispersion and by testing compositional changes due to turnover and nestedness among HALs and phytogeographical domains. Finally, we assessed which species were typical for each group using indicator species analysis. Bird homogenization was indicated by decreases in beta diversity following landscape changes. Beta diversity of rural sites was roughly half that of natural habitats, while urban sites held less than 10% of the natural areas’ beta diversity. Species composition analysis revealed that the turnover component was important in differentiating sites depending on HAL and phytogeography; the nestedness component was important among HALs, where directional species loss is maintained even considering effects of sampling effort. A similar result was obtained among phytogeographical domains, indicating nested-pattern dissimilarity among compositions of overlapping communities. As expected, a few native generalists and non-native urban specialists were characteristic of rural and urban sites. We generated strong evidence that taxonomic homogenization occurs in the south Brazilian Atlantic Forest as a result of a directional and nested species loss, with the resultant assemblages composed of few disturbance-tolerant birds.

Determinants of local and regional communities in intermittent and perennial headwaters of the Bolivian Amazon

Summary The effect of drying events on aquatic biodiversity is still overlooked in wet Neotropical systems. Yet, the responses of local communities and metacommunities in these biodiversity hotspots may differ from what is reported in other areas. We addressed the effect of drying events on local and regional fish and macroinvertebrate communities in the headwaters of the Chipiriri River basin, in the wet Neotropical piedmont of Bolivia. According to current knowledge in intermittent rivers and ephemeral streams (IRES) ecology, we predicted that intermittent (INT) sites would harbour lower α‐diversity, but higher β‐diversity, than perennial (PER) sites, due to local, negative effect of drying combined with the existence of multiple recovery stages at the network scale. Although habitat variables were similar between INT and PER sites, local and regional diversity patterns differed. Local invertebrate communities were not different between site types as soon as 4–6 weeks after flow resumption. The proximity of colonist sources and frequent rainfall probably enhanced persistence through dry periods and high resilience. In contrast, fish communities were still poorer at INT than PER sites, indicating they were still in the process of recolonising upstream INT reaches. β‐diversity analyses confirmed that invertebrate and fish metacommunities were not at the same recovery stage because (i) β‐diversity of invertebrates was best explained by physical and environmental distances at both INT and PER sites, whereas that of fish was explained only by physical distances at INT sites; (ii) fish β‐diversity was higher at INT than at PER sites, but invertebrate β‐diversity was similar; and (iii) physical distances were correlated with the turnover component of invertebrate β‐diversity but with the nestedness component for fish. Exploring regional community patterns in IRES and across biota with different dispersal abilities and modes can advance metacommunity theory and improve our ability to predict local community composition in dynamic ecosystems.

Contrasting metacommunity structure and beta diversity in an aquatic‐floodplain system

Habitat connectivity and dispersal interact to structure metacommunities, but few studies have examined these patterns jointly for organisms across the aquatic–terrestrial ecotone. We assessed metacommunity structure and beta diversity patterns of instream benthic invertebrates, riparian carabid beetles (Order: Coleoptera; Family: Carabidae) and riparian spiders (Order: Araneae) at fifteen sites in a river‐floodplain system. Sampling took place over a three‐year period (2010–2012) in the Rhine‐Main‐Observatory LTER site on the Kinzig River, central Germany. This allowed disentangling the combined influence, and temporal variability, of habitat connectivity (i.e. between aquatic and terrestrial) and dispersal ability (i.e. between spiders and beetles, and aerial and aquatic dispersing invertebrates) on the dominant paradigms structuring these metacommunities. We found mostly consistent differences in the manner that metacommunities were structured between groups, with lower levels of variability explained for beetles compared to the other groups. Beetles were consistently structured more by turnover than nestedness components, with greater beta diversity than expected by chance and a minor spatial compared to environmental signal emerging with variance partitioning. Conversely, spiders and benthic invertebrates had lower beta diversity and greater nestedness than null expectation, and a clearer spatial signal controlling metacommunity structure. Our results suggest varying levels of mass effects and species sorting shape river‐floodplain metacommunities, depending on habitat connectivity and dispersal ability. That is, greater connectivity and lower fragmentation along the river compared to the terrestrial zone promoted mass effects, and differences in overall dispersal ability and mode (i.e. active and passive) for instream and riparian communities shifted paradigms between mass effects and species sorting.

Geographical patterns of species richness and beta diversity of Larentiinae moths (Lepidoptera: Geometridae) in two temperate biodiversity hotspots

Biodiversity hotspots have been in the mainstream of studies and debates regarding conservation and biodiversity. Results, however, are skewed towards vertebrates and the tropics, and cannot simply be generalized to invertebrates and temperate biodiversity hotspot regions. In this first study of its kind, we explored the spatial patterns of Larentiinae moth (except genus Eupithecia Curtis, 1825) species richness and beta diversity in two neighbouring temperate biodiversity hotspots, the Caucasus and the Irano-Anatolian biodiversity hotspots, Middle Palearctic. We explored how spatial gradients contribute to the formation of moth species richness in these two biodiversity hotspots by disentangling beta diversity patterns to spatial turnover and nestedness components. Larentiinae moths showed a positive association with latitude and a unimodal relationship with elevation. The latitudinal gradient contributed more than the elevational gradient in formation of biodiversity. Both hotspots showed similar patterns of beta diversity partitioning, demonstrating a large contribution of spatial turnover to biodiversity formation. Constant high values of spatial turnover across 17° of latitudinal gradient may indicate that diversity has been formed by a consistent mechanism of horizontal species level diversification of larentine moths throughout mountains.

Patterns in species and functional dissimilarity: insights from periphytic algae in subtropical floodplain lakes

Understanding spatial and temporal changes in species composition has long demanded the attention of ecologists. However, only recently questionsrelatedtochangesinspecies functionaltraits have been investigated. We explored patterns of species andfunctionaldissimilarity ofperiphyticalgae at six lakes sampled over a year across a subtropical floodplain. We evaluated the importance of turnover and nestedness components across space and time; the influence of environmental dissimilarity, spatial dis- tance,andtimeonspecies andfunctionaldissimilarity; and whether functional dissimilarity results from non- stochastic assembly processes. We used six functional traits to describe 155 species. Functional dissimilarity was estimated by functional dendrograms, and stochasticity was evaluated using null models. The turnover component was greater than nestedness for species and functional dissimilarity. Environmental dissimilarity, spatial distance, or time did not signif- icantly explain species or functional dissimilarity. However, functional dissimilarity was significantly greater than expected given the observed species dissimilarity. The main finding of this study is that communityassemblywasdeterministicwithrespectto traits. Further, each lake contributed similarly to the overall species and traits pool. These results highlight the importance of comparing species and functional dissimilarities to reach a better understanding of the organization of periphytic algal communities.

Concordance and discordance between taxonomic and functional homogenization: responses of soil mite assemblages to forest conversion.

The compositional characteristics of ecological assemblages are often simplified; this process is termed "biotic homogenization." This process of biological reorganization occurs not only taxonomically but also functionally. Testing both aspects of homogenization is essential if ecosystem functioning supported by a diverse mosaic of functional traits in the landscape is concerned. Here, we aimed to infer the underlying processes of taxonomic/functional homogenization at the local scale, which is a scale that is meaningful for this research question. We recorded species of litter-dwelling oribatid mites along a gradient of forest conversion from a natural forest to a monoculture larch plantation in Japan (in total 11 stands), and collected data on the functional traits of the recorded species to quantify functional diversity. We calculated the taxonomic and functional β-diversity, an index of biotic homogenization. We found that both the taxonomic and functional β-diversity decreased with larch dominance (stand homogenization). After further deconstructing β-diversity into the components of turnover and nestedness, which reflect different processes of community organization, a significant decrease in the response to larch dominance was observed only for the functional turnover. As a result, there was a steeper decline in the functional β-diversity than the taxonomic β-diversity. This discordance between the taxonomic and functional response suggests that species replacement occurs between species that are functionally redundant under environmental homogenization, ultimately leading to the stronger homogenization of functional diversity. The insights gained from community organization of oribatid mites suggest that the functional characteristics of local assemblages, which support the functionality of ecosystems, are of more concern in human-dominated forest landscapes.