Variation In Beta Diversity Research Articles

High interannual variability of a climate-driven amphibian community in a seasonal rainforest

Seasonality exerts strong pressures on biodiversity patterns. Yet, temporal beta-diversity is poorly studied in tropical systems, and the drivers of variability in amphibian activity and seasonality remain largely unknown. We quantified intra- and interannual variation in temporal beta-diversity relying on a nine-year, year-round survey (51 species, n > 23,000) performed in a protected area (Betampona, Madagascar). We assessed the dependence on climate of beta-diversity and abundance using a distance-based redundancy analysis and generalised linear mixed models, respectively. Despite the majority of species being preferentially active during one specific period, beta-diversity and abundance were more variable between years than within years. Temporal variation in beta-diversity was best explained by temperature (but climate accounted for only 2% of variation). Species abundance was best explained by temperature (for 32% of the tested species), monthly humidity (30%) and monthly rainfall (24%). We found no climatic dependence for 24% of the species. Our results suggest that studies focusing on species phenology can be misleading when based on single-year surveys even in seasonal systems. The high interannual variability in diversity may be due to an adaptive responses to an important regime of stochastic events. Given the direction of the relationships between weather and abundances, we predict that a large proportion of amphibians would suffer from climate change in Madagascar. We emphasise the need to account for multiple temporal scales in studies of tropical species composition and abundance to better understand species phenology and their response to climate change, and make targeted conservation actions more effective.

Determinants of the beta diversity of tree species in tropical forests: Implications for biodiversity conservation

The mapping of earth’s biodiversity has advanced our theoretical and empirical understanding of biodiversity and has thus guided conservation efforts. Yet, early biodiversity maps often relied on alpha diversity indices, while beta diversity has rarely been used for practical conservation actions. We used generalized dissimilarity modelling (GDM) and variance partitioning to map beta diversity patterns of Hainan Island, China, and explore its underlying factors based on a large dataset of 248,538 individual trees belonging to 1,016 species in 902 forest plots. We used principal component analysis and hierarchical clustering to visualize community similarity, and spatial overlap analysis to assess the ability of the current protected areas (PAs) to encompass beta diversity. The GDMs explained 27.65% and 26.58% of the variation in beta diversity at the genus and species levels, respectively. The community composition of tree species in Hainan presented a general east-to-west gradient, and three floristic regions were delineated. This biogeographical pattern is predominantly structured by mean annual precipitation. Environmental variables, rather than geographical distance, were the most important factors determining present beta diversity patterns. Currently, PAs of Hainan Island are concentrated on mountain forest areas, while the lowland forest has largely been ignored. Thus, we suggest that biodiversity mapping based only on alpha diversity is not enough to identify conservation gaps, and the inclusion of beta diversity in such maps constitutes a promising tool to maximize the biodiversity coverage of PAs. Our study provides empirical evidence that a spatially explicit analysis of beta diversity in a specific region can be used for conservation planning.

Association of dietary patterns with the gut microbiota in older, community-dwelling men

While the gut microbiota is relatively stable through adulthood, its composition is influenced by various host and environmental factors, including changes in health, gastrointestinal processes (e.g., transit time, gastric acidity), medication use, and diet. The association of habitual diet, in the form of a posteriori-derived dietary patterns, and microbiota composition has not been adequately studied, particularly in older men. The objective was to investigate the association of dietary patterns with the composition and diversity of the gut bacterial microbiota in community-dwelling, older men. This cross-sectional study included 517 men who were participants in the Osteoporotic Fractures in Men (MrOS) Study (≥65 y of age at baseline in 2000-2002) and who provided a stool sample and completed an FFQ at MrOS Visit 4 in 2014-2016. Dietary patterns were derived by factor analysis. 16S ribosomal RNA target gene sequencing was performed and taxonomy assignments were derived using the Greengenes database. Linear regression and permutational multivariate analysis of variance (PERMANOVA) considered variations in alpha and beta diversity by dietary pattern, and a model that implements a 0-inflated Gaussian distribution of mean group abundance for each taxa (metagenomeSeq) assessed taxonomic variations by dietary pattern. In multivariable-adjusted models, greater adherence to the Western pattern was positively associated with families Mogibacteriaceae and Veillonellaceae and genera Alistipes, Anaerotruncus, CC-115, Collinsella, Coprobacillus, Desulfovibrio, Dorea, Eubacterium, and Ruminococcus, while greater adherence to the prudent pattern was positively associated with order Streptophyta, family Victivallaceae, and genera Cetobacterium, Clostridium, Faecalibacterium, Lachnospira, Paraprevotella, and Veillonella. The relative abundance of the dominant gut bacterial phyla, Bacteroidetes and Firmicutes, did not differ between participants with greater adherence to the Western pattern, compared with those with greater adherence to the prudent pattern. Dietary patterns were not associated with measures of alpha diversity, but beta diversity measures were significantly associated with both Western and prudent patterns. We observed significant associations between dietary patterns and measures of gut microbial composition in this sample of community-dwelling, older men.

Multiple processes at different spatial scales determine beta diversity patterns in a mountainous semi-arid rangeland of Khorassan-Kopet Dagh floristic province, NE Iran

The study of local and regional mechanisms driving spatial patterns in beta diversity is essential to the understanding of biodiversity. We aimed to predict the roles of multiple mechanisms operating at regional to fine spatial scales in structuring the beta diversity in a mountainous semi-arid rangeland of the Khorassan-Kopet Dagh floristic province located in NE Iran. We evaluated the relative contributions of three main filters, at the regional (stochastic but spatially structured dispersal filter), local (abiotic filter), and fine (biotic filter) spatial scales on beta diversity across communities. We partitioned beta diversity constrained by spatial, environmental, and biotic variables in 23 communities studied here, and used simple RDA and RDA-based variation partitioning to assess the contributions of studied filters on beta diversity. Moreover, spatial autocorrelation analyses were used to test neutral theory predictions. The relative contributions of the studied ecological filters explained 55% of variation in beta diversity. Although differences in the explained variations between unique fractions are low, the abiotic and biotic filters (signifying the niche-based processes) represent stronger effects directly and indirectly (via impact on significantly of other ecological filters) than dispersal (signifying neutral processes) on beta diversity. In addition, 45% of the variation in beta diversity was not explained by the studied ecological filters. In conclusion, independent and shared impacts of processes at different spatial scales determine beta diversity in our plant communities. However, unexplained variation in beta diversity requires further study of other facets of biodiversity and community assembly processes.

Untangling the assembly of macrophyte metacommunities by means of taxonomic, functional and phylogenetic beta diversity patterns

Metacommunity ecology has broadened considerably with the recognition that measuring beta diversity beyond the purely taxonomic viewpoint may improve our understanding of the dispersal- and niche-based mechanisms across biological communities. In that perspective, we applied a novel multidimensional approach including taxonomic, functional and phylogenetic data to enhance our basic understanding of macrophyte metacommunity dynamics. For each beta diversity metric, we calculated the mean overall value and tested whether the mean value was different from that expected by chance using null models. We also employed evolutionary and spatially constrained models to first identify the degree to which the studied functional traits showed a phylogenetic signal, and then to estimate the relative importance of spatial and environmental effects on metacommunity structure. We first found that most individual ponds were inhabited by species that were merely random draws from the taxonomic and phylogenetic species pool available in the study region. Contrary to our expectations, not all measured traits were conserved along the phylogeny. We also showed that trait and phylogenetic dimensions strongly increased the amount of variation in beta diversity that can be explained by degree of environmental filtering and dispersal limitation. This suggests that accounting for functional traits and phylogeny in metacommunity ecology helps to explain idiosyncratic patterns of variation in macrophyte species distribution. Importantly, phylogenetic and functional analyses identified the influence of underlying mechanisms that would otherwise be missed in an analysis of taxonomic turnover. Together, these results let us conclude that macrophyte species have labile functional traits adapted to dispersal-based processes and some evolutionary trade-offs that drive community assembly via species sorting. Overall, our exploration of different facets of beta diversity showed how functional and phylogenetic information may be used with species-level data to test community assembly hypotheses that are more ecologically meaningful than assessments of environmental patterns based on the purely taxonomic viewpoint.

Environmental Filtering Drives Plant Community Assembly Processes in the Riparian Marsh of Downstream Yellow River, China

The driver of plant community assembly in riparian marshes is vital but still unclear. In this study, we report the results of sixty plots located along the downstream Yellow River to identify the driver of plant community assemblages. Seven functional traits were measured and compiled to calculate functional beta diversity, and phylogenetic tree was constructed to assess phylogenetic dissimilarity. The analyses show that all of traits had weak phylogenetic signals using the Blomberg’s K statistic. The phylogenetic and functional beta diversity present clustering patterns, with the exception of leaf nitrogen concentration and leaf phosphorus concentration; and the standardized effect sizes based on multi-traits, maximum height, leaf dry matter content are well correlated with the environmental gradient. The findings imply that environment filtering was responsible for the variation of beta diversity, and drove community assembly in the riparian marsh. Of all environmental factors, soil salinity is the most crucial indicator to dominate the pattern of beta diversity.

Aquatic ecosystem changes in a global biodiversity hotspot: Evidence from the Albertine Rift, central Africa

AbstractAimDetermine the extent to which remote, high‐altitude (Afroalpine) aquatic ecosystems in tropical Africa have been impacted by global and regional‐scale environmental change processes.LocationTwo volcanic crater lakes (Bisoke and Muhavura) in the Afroalpine zone, Albertine (Western) Rift, central Africa.MethodsSediment cores were collected from Bisoke and Muhavura lakes and dated using radiometric techniques. A range of sediment‐based proxies was extracted from the cores and quantified. Sedimentary data were subjected to statistical analyses that contributed to the identification of influential environmental variables and their effects on diatom assemblages, the determination of variations in spatial beta diversity and estimates of the rate of compositional turnover over the last c. 1,200 years.ResultsSediments from the two sites provide evidence of the sensitivity of remote, Afroalpine aquatic ecosystems to perturbation. Climate variability has been a major driver of ecological change, particularly at Bisoke Lake, throughout the c. 1,200‐year‐long record, while Muhavura Lake has been directly impacted by and recovered from at least one volcanic eruption during this time. The effects of climatic warming from the mid‐ to late 19th century and especially from the late 20th century, possibly accentuated by atmospheric deposition‐driven nutrient enrichment, appear increasingly in lockstep. Effects include changes in diatom community composition, increased productivity and compositional turnover, and biotic homogenization (reduced spatial beta diversity) between the two sites.Main conclusionsThe two Afroalpine sites record changes in atmospheric conditions and their effects on diatom assemblage composition, particularly over the last c. 150 years. Drivers of these changes have the potential to disrupt ecosystems at lower altitudes in the Albertine Rift, including biodiverse areas of forest, and across tropical Africa more widely.

The effects of environment, hosts and space on compositional, phylogenetic and functional beta-diversity in two taxa of arthropod ectoparasites.

We studied the effects of variation in environmental, host-associated and spatial factors on variation in compositional, phylogenetic/taxonomic and functional facets of beta-diversity in fleas and gamasid mites parasitic on small mammals and asked whether (a) the importance of these factors as drivers of beta-diversity differs among its multiple facets and (b) the effects of variation in environment, hosts and space on beta-diversity variation differ between the two ectoparasite taxa. To understand the relative effects of each group of predictors, we used a distance-based redundancy analysis and variation partitioning. The greatest portions of variation in the compositional beta-diversity of fleas were equally explained by host-associated and spatial predictors, whereas variation in host species composition contributed the most to variation in the compositional beta-diversity of mites. Variation in the phylogenetic (i.e. based on phylogenetic tree) beta-diversity of fleas was mainly due to variation in the phylogenetic composition of host communities, while the taxonomic (i.e. based on Linnean taxonomy) beta-diversity of mites was influenced by environmental variation. Unique contributions of spatial and environmental variation explained most of the variation in functional beta-diversity and its species replacement (= turnover) component (i.e. beta-diversity explained by replacement of species alone) in fleas and mites, respectively. Variation in the richness difference component (i.e. beta-diversity explained by species loss/gain alone) of functional beta-diversity was mainly affected by either variation in the functional composition of host assemblages (fleas) or its joint action with environmental variables (mites). We conclude that the pattern of the relative effects of environmental, host-associated and spatial factors on beta-diversity is context-dependent and may differ among different facets of beta-diversity, among different beta-diversity components and also among taxa dependent on biological affinities.

Species turnover drives the spatial distribution of frog beta diversity in farmland ponds

AbstractStudies integrating variation in species composition among sites are useful in understanding the impacts of land-use changes on the spatial distribution of biodiversity. However, the failure to recognize the distinction between beta diversity components, dissimilarity due to species replacement (i.e. turnover) and dissimilarity due to species loss from site to site (i.e. nestedness), can lead to inappropriate use of some indices. Here, we evaluated how the spatial distribution of anuran beta diversity components, turnover and nestedness, is associated with local and landscape descriptors in a tropical agricultural landscape with a recent history of agriculture expansion in south-eastern Brazil. Overall, 27 anuran species were found in the region with average ± SD species richness in each pool of 9.5 ± 3.5 species, ranging from 4 to 15 species. We observed that species turnover was the major component for anuran dissimilarity among pools, indicating that anuran species occurring in species-poor pools are not subsets of anuran species occurring in species-rich pools. Local variables and geographic distance were not important descriptors explaining the variation of anuran beta diversity. In contrast, the distance of the pools to the nearest forest fragment explained 16% of the variance in total beta diversity, 5% of the nestedness component and 2% of spatial turnover. Our results show that pools distributed across farmland landscapes are harbouring different anuran species composition, and together, these pools are contributing to the regional diversity of anurans in this region which is considered one of the most deforested and fragmented within Brazil.

Beta diversity of stream fish communities along anthropogenic environmental gradients at multiple spatial scales.

Despite the importance of assessing beta diversity to understand the effects of human modifications on biological communities, there are almost no studies that properly addressed how beta diversity varies along anthropogenic gradients. We developed an algorithm to calculate beta diversity among a set of sites included in a moving window along any given environmental gradient. This allowed us to assess beta diversity among sites with similar conditions in terms of human modifications (e.g., land use or instream degradation). We investigated beta diversity using stream fish community data and indicators of human modification quantified at four spatial scales (whole catchment, riparian, local, and instream). Variation in beta diversity was dependent on the scale of human modifications (catchment, riparian, local, instream, and all four scales combined) and on the type of diversity considered (taxonomic or functional). We also found evidence for non-linear responses of both taxonomic and functional beta diversity to human-induced environmental alterations. Therefore, the response of beta diversity was more complex than expected, as it depended on the scale used to quantify human impact and exhibited opposite responses depending on the location along the environmental impact gradient and on whether the response was taxonomic or functional diversity. Anthropogenic modifications can introduce unexpected variability among stream communities, which means that low beta diversity may not necessarily indicate a degraded environmental condition and high beta diversity may not always indicate a reference environmental condition. This has implications for how we should consider beta diversity in environmental assessments.

Decoupling species richness variation and spatial turnover in beta diversity across a fragmented landscape

BackgroundHow habitat fragmentation affects the relationship between local richness and the variation in community composition across space is important to both ecology and conservation biology, but this effect remains poorly understood.MethodsHere, we present an empirical study to address this topic in a fragmented landscape, the Thousand Island Lake (TIL), an artificial land-bridge island system with more than 1,000 islands, which provides an “experimental” fragmented landscape with a homogeneous matrix and similar successional history. We measured species composition and plant functional type (PFT) on 29 islands, and tested the effects of island area and isolation on the relationship between α- and β-diversity. General Linear Models were applied to test the impact of habitat fragmentation. In addition, variation partitioning was used to decouple α-diversity dependent and α-diversity independent spatial turnover in β-diversity of the plant community and across different PFTs.ResultsWe found habitat fragmentation influences β-diversity of plants primarily by modifying local α-diversity, not spatial turnover in the TIL system. We also found area-dependent environmental filtering and differential plant responses across functional types were the most likely underlying driving mechanisms.DiscussionThese results highlight the importance of hierarchical linkages between components of biodiversity across scales in fragmented landscapes, and have practical conservation implications.

Environmental toxicants in breast milk of Norwegian mothers and gut bacteria composition and metabolites in their infants at 1\xa0month

BackgroundEarly disruption of the microbial community may influence life-long health. Environmental toxicants can contaminate breast milk and the developing infant gut microbiome is directly exposed. We investigated whether environmental toxicants in breastmilk affect the composition and function of the infant gut microbiome at 1 month. We measured environmental toxicants in breastmilk, fecal short-chain fatty acids (SCFAs), and gut microbial composition from 16S rRNA gene amplicon sequencing using samples from 267 mother-child pairs in the Norwegian Microbiota Cohort (NoMIC). We tested 28 chemical exposures: polychlorinated biphenyls (PCBs), polybrominated flame retardants (PBDEs), per- and polyfluoroalkyl substances (PFASs), and organochlorine pesticides. We assessed chemical exposure and alpha diversity/SCFAs using elastic net regression modeling and generalized linear models, adjusting for confounders, and variation in beta diversity (UniFrac), taxa abundance (ANCOM), and predicted metagenomes (PiCRUSt) in low, medium, and high exposed groups.ResultsPBDE-28 and the surfactant perfluorooctanesulfonic acid (PFOS) were associated with less microbiome diversity. Some sub-OTUs of Lactobacillus, an important genus in early life, were lower in abundance in samples from infants with relative “high” (> 80th percentile) vs. “low” (< 20th percentile) toxicant exposure in this cohort. Moreover, breast milk toxicants were associated with microbiome functionality, explaining up to 34% of variance in acetic and propionic SCFAs, essential signaling molecules. Per one standard deviation of exposure, PBDE-28 was associated with less propionic acid (− 24% [95% CI − 35% to − 14%] relative to the mean), and PCB-209 with less acetic acid (− 15% [95% CI − 29% to − 0.4%]). Conversely, PFOA and dioxin-like PCB-167 were associated with 61% (95% CI 35% to 87%) and 22% (95% CI 8% to 35%) more propionic and acetic acid, respectively.ConclusionsEnvironmental toxicant exposure may influence infant gut microbial function during a critical developmental window. Future studies are needed to replicate these novel findings and investigate whether this has any impact on child health.

The Influence of Abiotic Environment and Connectivity on the Distribution of Diversity in an Andean Fish Fluvial Network

Abstract The distribution of Andean freshwater fishes is the result of the interaction of historical and contemporary factors such as basin geomorphology and the physicochemical characteristics of the water bodies. Dramatic changes along the river network due to waterfalls or dams generate dramatic changes in longitudinal slopes and fish assemblages because they function as ecological barriers to dispersal. We expect the amount of variation in beta diversity along the elevation gradient (between 700 and 3,500 m a.s.l.) of the eastern slope of the Cauca River basin to be explained by changes in the water environment and connectivity among sites. We measured connectivity in terms of the distance in the stream channel between sampling sites considering changes in slope. We used a Generalized Dissimilarity Model (GDM) to evaluate the contribution of connectivity and other water mass characteristics (dissolved oxygen, pH, conductivity, temperature, and elevation) in predicting changes in beta diversity. The GDM models explained 33% of the total variance in species turnover, suggesting that there are additional variables that have not been considered, such as available habitats along the rivers. Elevation was the variable with the largest relative importance in the model and connectivity only explained seven percent of the total variance when all sites were included. However, when only the sampling sites in the stream headers were included (most geographically isolated sites), the contribution due to connectivity increased to 51%. Isolation of stream headers, in conjunction with extreme conditions such as low water temperature, may influence the fish assemblage turnover. Our results provide evidence that elevation has a strong influence on beta diversity of Andean fish assemblages. Species turnover upstream above 1,200 m a.s.l. is strongly influenced by channel connectivity and there are additional environmental variables that need to be included in the models to improve their prediction power.

Community structure of woody plants on islands along a bioclimatic gradient

Understanding patterns of community structure and the causes for their variation can be furthered by comparative biogeographic analyses of island biotas. We used woody plant data at the local scale to investigate variations in species rarity, alpha, beta, and gamma diversity within and between three islands from the oceanic archipelagoes of Azores, Canaries and Mascarene. We used standardized protocols to sample ten 50 m × 50 m forest plots in each of the three islands with contrasting climate and regional species pools: Terceira (Azores), Tenerife (Canaries), and Reunion (Mascarene Islands). Occupancy frequency distributions and species abundance distributions were used to investigate rarity. The partitioning of beta diversity in a distance-decay framework was used to test for spatial patterns of community composition. Rarity was much more pronounced in the highly diverse islands of Tenerife and Reunion than in the regionally poorer island of Terceira. The number of species rose faster with increasing sample area in both Tenerife and Reunion. The slope of the species rank abundance curve was steeper in Terceira whereas the richer island assemblages approached a lognormal model. Compositional changes according to spatial distance were mostly due to replacement of species in Terceira and Reunion. Our results point to important differences in the community structure of Terceira, which is the less diverse and temperate region in comparison to Tenerife and Reunion which are highly diverse.

Different roles for geography, energy and environment in determining three facets of freshwater molluscan beta diversity at broad spatial scales

Current understanding of different facets of beta diversity and their underlying determinants remains limited at broad scales in the freshwater realm. We examined the geographical patterns and spatial congruence of three beta diversity facets of freshwater molluscs across all of China, and evaluated the relative importance of environmental and spatial factors underlying the observed patterns. Taxonomic (β-TD), functional (β-FD) and phylogenetic (β-PD) beta diversity were calculated for 212 drainage basins belonging to 10 hydrographic regions using compiled occurrence data of 313 molluscan species. Geographical patterns of the three diversity facets were visualized on maps and pairwise spatial congruence among them was evaluated using regression on distance matrices. Variation partitioning and multivariate regression trees were used to assess the relative importance of different factors underlying beta diversity patterns. Beta diversity maps revealed that geographical patterns of β-TD and β-PD showed strong spatial clustering and were well matched with hydrographic regions' boundaries, while β-FD showed only moderate spatial aggregation. The three facets were only moderately congruent, with over 60% of the variation in one facet remaining unexplained by any other facet. Remarkably, all diversity facets were best explained by the spatial factors with considerable unique effects. Environmental filtering associated with energy gradients also made a large contribution, while habitat availability only explained minor fractions of the variation in beta diversity. At the national scale, β-TD and β-PD were more strongly related to spatial processes, whereas β-FD was more strongly associated with energy gradients. Our results suggested that, for freshwater organisms with low dispersal capacity, dispersal processes may override environmental filtering in driving geographical diversity patterns. However, different ecological drivers were important for each diversity facet. Importantly, rather weak spatial congruence among the different diversity facets stresses the need to incorporate functional and phylogenetic facets into the development of conservation planning.

Predicting beta diversity of terrestrial and aquatic beetles using ecogeographical variables: insights from the replacement and richness difference components

AbstractAimWe examined the responses of the beta diversity of aquatic and terrestrial beetles to ecogeographical variables, including climate, land cover and land use, across Northern Europe.LocationNorthern Europe (Denmark, Sweden, Norway and Finland).MethodsInformation on the occurrence of ground beetles and diving beetles across Northern European biogeographical provinces was collated from literature sources. Beta diversity was examined using Jaccard dissimilarity coefficient as well as its replacement and richness difference components. Each of the three dissimilarity matrices (responses) was modelled using various ecogeographical variables (predictors) by generalized dissimilarity modelling (GDM).ResultsThe magnitude of total beta diversity was relatively similar between ground beetles and diving beetles, but the richness difference component contributed more than the replacement component to total beta diversity in ground beetles, whereas the opposite was true for diving beetles. The predictor variables most influential in GDM in accounting for spatial variation in beta diversity varied between the two beetle groups as well as between the replacement and richness difference components. In general, the richness difference component of ground beetles responded strongly to latitude and associated climatic variables, whereas the replacement component of diving beetles varied strongly along the same geographical gradient.Main conclusionsOur findings suggest that the study of the determinants of biodiversity patterns benefits from the partitioning of beta diversity into different components and from comparing terrestrial and aquatic groups. For example, our findings suggest that the strong climatic and land use‐related gradients in beta diversity have important implications for predicting and mitigating the effect of ongoing global change on the composition of regional biotas.

Cross-taxon congruence in insect responses to fragmentation of Brazilian Atlantic forest

Anthropogenic disturbance causes many impacts across multiple levels of biological organization from populations to ecosystems. However, the extent of cross-taxon congruence in biotic responses to disturbance, and therefore the utility of using particular taxa as indicators of broader biotic responses, is poorly known. In this study, we examine the extent to which variation in alpha diversity, beta diversity and species composition of ants, fruit-feeding butterflies, dung beetles and termites in relation to fragment size are congruent in the highly fragmented Brazilian Atlantic forest. Our results show generally low and inconsistent congruence, typically occurring for particular pairs of taxa only (such as butterflies and dung beetles for species composition, and ants and termites for Hill diversity-1D) or not at all (such as for species richness). In synthesis, there some universal community-level attributes and taxa (i.e., attributes responding consistently and congruently across taxa) have been proved to be sensitive in general. Vegetation structure and spatial location of fragments were not significant predictors of ant and termite species composition, but explained 21% and 40% of the variation in species composition of dung beetles and butterflies, respectively. In addition, we found no general increase in the ratio of generalists to specialists with decreasing fragment size. The overall lack of cross-taxon congruence means that a single taxon cannot provide a reliable indication of biotic responses to fragmentation in our study system. This can be explained by taxon-specific responses to variation in tree diversity, tree functional attributes and the spatial location of fragments. Our study therefore provides support for a multi-taxon approach to biodiversity monitoring and conservation planning.

Local environment and space drive multiple facets of stream macroinvertebrate beta diversity

AbstractAimUnderstanding variation in biodiversity typically requires consideration of factors operating at different spatial scales. Recently, ecologists and biogeographers have recognized the need of analysing ecological communities in the light of multiple facets including not only species‐level information but also functional and phylogenetic approaches to improve our understanding of the relative contribution of processes shaping biodiversity. Here, our aim was to disentangle the relative importance of environmental variables measured at multiple levels (i.e., local, catchment, climate, and spatial variables) influencing variation in macroinvertebrate beta diversity facets (i.e., species, traits, and phylogeny) and their components (i.e., replacement and abundance difference) in boreal streams.TaxonAquatic macroinvertebratesLocationWestern FinlandMethodsA total of 105 streams were sampled in western Finland, encompassing a geographical extent over 500 km. We analysed variation in the different beta diversity facets and components using distance‐based redundancy analysis and associated variation partitioning procedures. We modelled spatial structures using distance‐based Moran eigenvector maps.ResultsWe found that the relative influence of explanatory variables on each diversity facet and component revealed relatively similar patterns. Our main finding was that local environmental and spatial variables generally contributed most to the total explained variability in all facets and components of beta diversity, whereas catchment and climate variables explained less variation in the beta diversity facets at the spatial scale considered in this study.Main conclusionsDifferent facets of beta diversity were mainly influenced by local environmental variables and spatial structuring, likely acting through deterministic and stochastic pathways respectively. Identifying the ecological variables and mechanisms that drive variation in beta diversity may be used to guide the conservation and restoration efforts for biodiversity under global change.

Local-scale determinants of arboreal spider beta diversity in a temperate forest: roles of tree architecture, spatial distance, and dispersal capacity.

Spiders are a functionally important taxon in forest ecosystems, but the determinants of arboreal spider beta diversity are poorly understood at the local scale. We examined spider assemblages in 324 European beech (Fagus sylvatica) trees of varying sizes across three forest stands in Würzburg (Germany) to disentangle the roles of tree architecture, spatial distance, and dispersal capacity on spider turnover across individual trees. A large proportion of tree pairs (66%) showed higher compositional dissimilarity in spider assemblages than expected by chance, suggesting prominent roles of habitat specialization and/or dispersal limitation. Trees with higher dissimilarity in DBH and canopy volume, and to a lesser extent in foliage cover, supported more dissimilar spider assemblages, suggesting that tree architecture comprised a relevant environmental gradient of sorting spider species. Variation partitioning revealed that 28.4% of the variation in beta diversity was jointly explained by tree architecture, spatial distance (measured by principal coordinates of neighbor matrices) and dispersal capacity (quantified by ballooning propensity). Among these, dispersal capacity accounted for a comparable proportion as spatial distance did (6.8% vs. 5.9%). Beta diversity did not significantly differ between high- and low-vagility groups, but beta diversity in species with high vagility was more strongly determined by spatially structured environmental variation. Altogether, both niche specialization, along the environmental gradient defined by tree architecture, and dispersal limitation are responsible for structuring arboreal spider assemblages. High dispersal capacity of spiders appears to reinforce the role of niche-related processes.

Archipelago reserves, a new option to protect montane entomofauna and beta-diverse ecosystems

Beta diversity is often a dominant characteristic in mountain systems and naturally fragmented ecosystems. However, natural protected areas are traditionally designed to protect ecosystems with high alpha and low beta diversity. Recent information about dung beetles of the Transmexican Volcanic Belt was used to identify the most suitable strategy for the conservation of insect biodiversity in montane and beta-diverse ecosystems. Mean alpha diversity by mountain represents 38% of regional diversity. Most of the variation in beta diversity is explained because each mountain represents a unique habitat hosting a highly differentiated community. National parks appear to be inefficient to protect the high beta diversity shown by Mexican temperate mountains, especially for insect communities adapted to fragile ecosystems. The Archipelago Reserve scheme seems to be a suitable alternative to protect montane entomofauna and beta-diverse ecosystems. Our study reveals beta diversity patterns and complementarity among sites in a montane system, representing a first step to detect a suitable region for establishing an Archipelago Reserve in the Transmexican Volcanic Belt. Nevertheless, an analysis that matches current diversity patterns and protected areas is required to establish the best configuration for future reserves.