Generalized Dissimilarity Models Research Articles

Temporal changes in spatial scale and autocorrelation structure of forest openings based on taxonomic, phylogenetic, and functional turnover

ContextDuring European settlement, Illinois grasslands were converted for agricultural purposes. Remaining natural areas in southern Illinois include natural xeric forest openings, with communities representative of remnant grasslands and adjacent hardwood forests. Previous research in these openings shows plant communities are driven by edaphic conditions. ObjectivesThe first objective aimed to characterize spatial scale and autocorrelation structure of these openings based on climatic, environmental, and diversity variables. The second objective was to predict taxonomic, phylogenetic, and functional turnover between 1988 and 2019, using climatic and environmental variables. MethodsSurveys were conducted to calculate taxonomic, phylogenetics and functional trait metrics and analyses of these dimensions of diversity. Randomization tests were used to assess phylogenetic and functional clustering and over-dispersion at each site. Spatially-explicit climatic and environmental variables were included from earlier surveys and data repositories. Global Moran's I and spatial autocorrelograms were used to assess spatial structure of climatic, environmental, and diversity variables and generalized dissimilarity modeling was used to characterize taxonomic, phylogenetic, and functional turnover based on environmental variables. ResultsSoil depth was the only environmental variable which exhibited significant global spatial autocorrelation. Overall, sandstone sites were phylogenetically over-dispersed while loess sites were phylogenetically clustered. Climate variables and diversity metrics exhibited significant spatial structure during surveys. Generalized dissimilarity models showed that geographic distance between openings was the most influential driver of turnover across surveys. ConclusionsPrevious glacial events explained the spatial structure of soil depth across sites, due to Quaternary loess deposition in loess sites. High diversity values were clustered in the southeastern portions of the study area. Functional generalized dissimilarity models best predicted turnover in these openings compared to taxonomic and phylogenetic models.

Urbanization drives biotic homogenization of the avian community in China.

Urbanization-driven biotic homogenization has been recorded in various ecosystems on local and global scales; however, it is largely unexplored in developing countries. Empirical studies on different taxa and bioregions show conflicting results (i.e. biotic homogenization vs. biotic differentiation); the extent to which the community composition changes in response to anthropogenic disturbances and the factors governing this process, therefore, require elucidation. Here, we used a compiled database of 760 bird species in China to quantify the multiple-site β-diversity and fitted distance decay in pairwise β-diversities between natural and urban assemblages to assess whether urbanization had driven biotic homogenization. We used generalized dissimilarity models (GDM) to elucidate the roles of spatial and environmental factors in avian community dissimilarities before and after urbanization. The multiple-site β-diversities among urban assemblages were markedly lower than those among natural assemblages, and the distance decays in pairwise similarities in natural assemblages were more rapid. These results were consistent among taxonomic, phylogenetic, and functional aspects, supporting a general biotic homogenization driven by urbanization. The GDM results indicated that geographical distance and temperature were the dominant predictors of avian community dissimilarity. However, the contribution of geographical distance and climatic factors decreased in explaining compositional dissimilarities in urban assemblages. Geographical and environmental distances accounted for much lower variations in compositional dissimilarities in urban than in natural assemblages, implying a potential risk of uncertainty in model predictions under further climate change and anthropogenic disturbances. Our study concludes that taxonomic, phylogenetic, and functional dimensions elucidate urbanization-driven biotic homogenization in China.

Spatial patterns of β-diversity under cumulative pressures in the Western Mediterranean Sea

Understanding the spatial dynamics of biodiversity is an essential issue in marine ecology and requires combining information at local and regional scales. β-diversity is an important measure of biodiversity that informs on the differences in community composition between sites and, thus, in the species turnover in the community structure. In this study, we analysed and predicted the spatial patterns of β-diversity for fishes, invertebrates and the demersal assemblage along the Iberian Mediterranean coast. We used Bayesian Bootstrap Generalized Dissimilarity Models (BBGDMs) to study the effects of environment and human pressures on the β-diversity of invertebrate, fishes and the entire demersal assemblage from 1994 to 2015 using different time windows to account for temporal variability. Then, we used these relationships to predict the spatial patterns of β-diversity in the whole Iberian Mediterranean coast. Our results highlighted that the regional spatial patterns of β-diversity were best described by bathymetry and a cumulative index of coastal impacts. We identified specific regions with the highest β-diversity in the study area, which were complementary to hotspots of species richness and presented different degree of overlapping with existent marine protected areas. Overall, our study illustrates that by modelling spatial turnover using β-diversity we can better understand and predict spatial variation of biodiversity and the effects of particular variables, providing relevant information to end-users and policy makers for designing specific spatial conservation and management strategies.

Regional climate contributes more than geographic distance to beta diversity of copepods (Crustacea Copepoda) between caves of Italy

Despite the study of subterranean biodiversity facing harsh sampling and mapping challenges, the huge diversity of taxa, ecological adaptations and evolutionary trajectories in subterranean environments is gaining increasing attention. Yet, the spatial and environmental factors driving the composition of groundwater communities are still poorly understood. To partially fill this knowledge gap, we collected copepod crustaceans from 12 caves along the Italian peninsula between 2019 and 2022, sampling each cave twice. The resulting presence-absence data were analysed to assess: (i) between-cave taxonomic beta diversity, also partitioning between turnover and nestedness-resultant dissimilarity; (ii) the relative weight of geographic distance and climatic differences in shaping observed beta diversity. Seventy-one species of copepods were collected overall. Pairwise beta diversity was high for most pairs of caves, with turnover being the major component. Geographic distance-decay models partially explained total beta diversity and turnover patterns. However, in Generalized Dissimilarity Models (GDM), including surface climatic conditions as predictors, the contribution of seasonal temperature averages was generally higher than that of geographic distance. Further, the explanatory and predictive performance of the GDMs notably increased, along with temperature contribution, when widening the spatial extent from which climate data were gathered. Our results confirmed a high spatial turnover in groundwater copepods’ assemblages and strengthened the link between regional climate and subterranean biodiversity.

Beyond taxonomic diversity patterns - investigating how α and β components of macrophyte functional diversity respond to environmental gradients in lotic ecosystems of Greece.

In addition to quantifying the taxonomic diversity of aquatic communities, understanding the patterns of alpha functional diversity (α-diversity) and exploring changes in functional dissimilarity (β-diversity) can improve our understanding on how ecosystems respond to environmental changes. In this study, we quantified functional alpha (α) and beta (β) diversity of macrophytic assemblages from river sites in Greece and then, examined relationships with water quality parameters and hydromorphological factors. We assigned 6 traits (Ellenberg nutrients indicator, Ellenberg light indicator, growth form, leaf size, leaf type, fruit size) to a total of 36 hydrophyte species and calculated three indices of functional diversity (functional richness, functional dispersion and functional evenness). We also estimated the total β-functional diversity and its' main components, turnover and nestedness. To assess the effects of water quality (including physical and chemical variables) we used Generalized Additive Models (GAM) for alpha functional diversity indices and Generalized Dissimilarity Models (GDM) for beta functional diversity. We performed Kruskal-Wallis tests and permutational multivariate analysis of variance (PERMANOVA) to search for significant variations of α- and β-diversity among the hydromorphological factors. Our results showed that macrophyte growth form and light preference were important trait characteristics that explained a large share of the total variance of functional composition. We also found relatively low taxonomic and functional richness, whereas taxonomic and functional dissimilarity were mostly attributed to species turnover, which expresses the changes in taxonomic and functional composition. We found significant relationships between functional dispersion and functional evenness with pH and oxygen saturation, whereas functional dissimilarity was driven only by geographic distance, although the GDM explained a small portion of the total variance. Functional richness, dispersion and evenness were significantly higher at systems with fine substrates and deep waters with low or high flow compared to systems with coarser substrates and riffle habitats. We also found significant variation in functional dissimilarity among the hydromorphological factors, although much of the total variance remained unexplained. Overall, our study highlights the importance of considering the functional diversity of aquatic plant assemblages within the frame of freshwater monitoring and conservation plans.

Agricultural drivers of field margin plant communities are scale-dependent

In recent decades, agricultural intensification has led to a strong decline in biodiversity. Field margins act as shelters and dispersal corridors for biodiversity in highly disturbed landscapes, and are critical to the maintenance of ecosystem services. However, they are also impacted by agricultural practices in neighboring fields. Agricultural impacts are often studied at field to landscape scales, and rarely across biogeographic regions. One of the challenges in large-scale studies is the lack of standardized monitoring schemes including both biodiversity and accurate estimation of agricultural practices. Here, we take advantage of a national monitoring scheme in 462 sites in France, to assess the effects of agricultural practices on field margin flora at different extents and resolutions. We used spatial simultaneous autoregressive and generalized dissimilarity models to assess the response of plant richness and composition to climatic, soil and landscape conditions, and to agricultural (fertilization, herbicides) and margin management drivers. Analyses were repeated at the site-level, 40 and 75 km resolutions, and at regional and national extents. We found that the impact of agricultural practices on species richness was most important at the site-level, whereas climate and crop diversity became more important at the 75 km resolution. Compositional variations responded differently, with climate being more important at the site-level, and fertilization and crop diversity at the coarsest resolution. There was a strong variation in the variance explained by models among regions, but climate effects were weaker within biogeographic units compared to the national level, and different agricultural practices stood out as influential in different regions, suggesting that the regional context is fundamental in determining plant community structure. To efficiently conserve biodiversity, we therefore recommend the implementation of agricultural measures adapted to each region.

How Biodiversity, Climate and Landscape Drive Functional Redundancy of British Butterflies.

Biodiversity promotes the functioning of ecosystems, and functional redundancy safeguards this functioning against environmental changes. However, what drives functional redundancy remains unclear. We analyzed taxonomic diversity, functional diversity (richness and β-diversity) and functional redundancy patterns of British butterflies. We explored the effect of temperature and landscape-related variables on richness and redundancy using generalized additive models, and on β-diversity using generalized dissimilarity models. The species richness-functional richness relationship was saturating, indicating functional redundancy in species-rich communities. Assemblages did not deviate from random expectations regarding functional richness. Temperature exerted a significant effect on all diversity aspects and on redundancy, with the latter relationship being unimodal. Landscape-related variables played a role in driving observed patterns. Although taxonomic and functional β-diversity were highly congruent, the model of taxonomic β-diversity explained more deviance than the model of functional β-diversity did. Species-rich butterfly assemblages exhibited functional redundancy. Climate- and landscape-related variables emerged as significant drivers of diversity and redundancy. Τaxonomic β-diversity was more strongly associated with the environmental gradient, while functional β-diversity was driven more strongly by stochasticity. Temperature promoted species richness and β-diversity, but warmer areas exhibited lower levels of functional redundancy. This might be related to the land uses prevailing in warmer areas (e.g., agricultural intensification).

Climate, host and geography shape insect and fungal communities of trees

Non-native pests, climate change, and their interactions are likely to alter relationships between trees and tree-associated organisms with consequences for forest health. To understand and predict such changes, factors structuring tree-associated communities need to be determined. Here, we analysed the data consisting of records of insects and fungi collected from dormant twigs from 155 tree species at 51 botanical gardens or arboreta in 32 countries. Generalized dissimilarity models revealed similar relative importance of studied climatic, host-related and geographic factors on differences in tree-associated communities. Mean annual temperature, phylogenetic distance between hosts and geographic distance between locations were the major drivers of dissimilarities. The increasing importance of high temperatures on differences in studied communities indicate that climate change could affect tree-associated organisms directly and indirectly through host range shifts. Insect and fungal communities were more similar between closely related vs. distant hosts suggesting that host range shifts may facilitate the emergence of new pests. Moreover, dissimilarities among tree-associated communities increased with geographic distance indicating that human-mediated transport may serve as a pathway of the introductions of new pests. The results of this study highlight the need to limit the establishment of tree pests and increase the resilience of forest ecosystems to changes in climate.

Uncovering the determinants of biodiversity hotspots in China: Evidence from the drivers of multiple diversity metrics on insect assemblages and implications for conservation

Understanding large-scale biodiversity patterns and underlying mechanisms during the formation process is essential for guiding conservation efforts. However, previous studies on the identification and formation mechanism of diversity hotspots in China were often limited to a single (alpha) diversity metric, while multiple (beta or zeta) diversity has rarely been used for exploring drivers and conservation actions. Here, a comprehensive species distribution dataset consisting of representative families of three insect orders was compiled to explore biodiversity hotspots based on different algorithms. Furthermore, to assess the effects of environmental factors on hotspots, we fitted generalized additive mixed-effects models (GAMMs) for species richness, generalized dissimilarity models (GDMs) and multi-site generalized dissimilarity modeling (MS-GDM) for the total beta and zeta diversity. Our results showed that biodiversity hotspots were mainly concentrated in central and southern China, especially in mountainous areas with complex topography, which indicated the insects' affinity to montane environments. Further analyses based on multiple models showed that water-energy factors exerted the strongest explanatory power for the insect assemblage diversity in hotspots of both alpha and beta (or zeta) levels. Additionally, anthropogenic factors also exerted a significant effect on hotspots, and this effect was higher for beta diversity than for alpha diversity. Overall, our study elucidates a comprehensive analysis of the identification and underlying mechanism of biodiversity hotspots in China. Despite several limitations, we still believe that our findings can provide some new insights for conservation efforts in Chinese hotspots.

Revealing the drivers of parasite community assembly: using avian haemosporidians to model global dynamics of parasite species turnover

Why do some regions share more or fewer species than others? Community assembly relies on the ability of individuals to disperse, colonize and thrive in new regions. Therefore, many distinct factors, such as geographic distance and environmental features, can determine the odds of a species colonizing a new environment. For parasites, host community composition (i.e. resources) also plays a key role in their ability to colonize a new environment as they rely on their hosts to complete their life cycle. Thus, variation in host community composition and environmental conditions should determine parasite turnover among regions. Here, we explored the global drivers of parasite turnover using avian malaria and malaria‐like (haemosporidian) parasites. We compiled global databases on avian haemosporidian lineages distributions, environmental conditions, avian species distributions and functional traits, and ran generalized dissimilarity models to uncover the main drivers of parasite turnover. We demonstrated that haemosporidian parasite turnover is mainly driven by geographic distance followed by host functional traits, environmental conditions and host distributions. The main host functional traits associated with high parasite turnover were the predominance of resident (i.e. non‐migratory) species and strong territoriality, while the most important climatic drivers of haemosporidian turnover were mean temperature and temperature seasonality. Overall, we established the importance of geographic distance as a key predictor of ecological dissimilarity and showed that host resources influence parasite turnover more strongly than environmental conditions. We also evidenced that parasite turnover is most pronounced among tropical and less interconnected regions (i.e. regions with mostly territorial and non‐migratory hosts). Our findings provide a robust foundation for the prediction of avian pathogen spread and the emergence of infectious diseases.

Replacement drives native β‐diversity of British avifauna, while richness differences shape alien β‐diversity

AbstractAimWe explored the range shifts of alien and native birds, the responses of alien and native β‐diversity to abiotic factors, and the effect of native diversity on alien β‐diversity in two time periods.LocationGreat Britain.Time period1968–1972, 2007–2011.Taxa studiedBreeding birds.MethodsWe estimated range shifts of alien and native species between the periods 1968–1972 and 2007–2011. Following, β‐diversity of alien and native communities was estimated by Jaccard pairwise index (βtot) and partitioned into richness difference and replacement component for each period. We built abiotic generalized dissimilarity models including abiotic factors for alien and native βtot and their components and a biotic model for aliens including native taxonomic and functional diversity as predictors.ResultsMost alien and half native species expanded into new regions during the 40‐year period. The native species range shifts did not exhibit a clear pattern along the longitudinal or latitudinal gradient, while alien species tended to move north‐westwards. The richness difference was the dominant component of alien β‐diversity, and the replacement component contributed mostly to native β‐diversity. Alien β‐diversity responded similarly but less strongly than native β‐diversity, to the abiotic gradients. Temperature‐related variables, distance and precipitation were the most important abiotic drivers of native and alien β‐diversity. The biotic model of alien β‐diversity explained more deviance than the abiotic model.Main conclusionsAlien species expanded into new regions over the 40 years, with alien β‐diversity driven mostly by species gains. The effect of environmental filtering on alien communities was weaker compared with native communities but was slightly reinforced in the second period compared with the first period, highlighting the role of environmental change in shaping diversity patterns. Native diversity played a key role in driving alien β‐diversity, through biotic interactions or/and by reflecting climatic suitability or niche availability for aliens.

Population connectivity and genetic offset in the spawning coral Acropora digitifera in Western Australia.

Anthropogenic climate change has caused widespread loss of species biodiversity and ecosystem productivity across the globe, particularly on tropical coral reefs. Predicting the future vulnerability of reef‐building corals, the foundation species of coral reef ecosystems, is crucial for cost‐effective conservation planning in the Anthropocene. In this study, we combine regional population genetic connectivity and seascape analyses to explore patterns of genetic offset (the mismatch of gene–environmental associations under future climate conditions) in Acropora digitifera across 12 degrees of latitude in Western Australia. Our data revealed a pattern of restricted gene flow and limited genetic connectivity among geographically distant reef systems. Environmental association analyses identified a suite of loci strongly associated with the regional temperature variation. These loci helped forecast future genetic offset in gradient forest and generalized dissimilarity models. These analyses predicted pronounced differences in the response of different reef systems in Western Australia to rising temperatures. Under the most optimistic future warming scenario (RCP 2.6), we predicted a general pattern of increasing genetic offset with latitude. Under the extreme climate scenario (RCP 8.5 in 2090–2100), coral populations at the Ningaloo World Heritage Area were predicted to experience a higher mismatch between current allele frequencies and those required to cope with local environmental change, compared to populations in the inshore Kimberley region. The study suggests complex and spatially heterogeneous patterns of climate‐change vulnerability in coral populations across Western Australia, reinforcing the notion that regionally tailored conservation efforts will be most effective at managing coral reef resilience into the future.

Fish zeta diversity responses to human pressures and cumulative effects across a freshwater basin

AbstractAimDeclining biodiversity across ecosystems and myriad human pressures necessitate high‐level regional assessments for effective management. Evaluation of biodiversity patterns and stressor accumulation through beta diversity and cumulative effect analyses are two key methods for management prioritization. This study links these concepts to develop a novel cumulative effect metric based on beta diversity responses.LocationFraser River basin, British Columbia, Canada.MethodsMulti‐Site Generalized Dissimilarity Models were used to evaluate nonlinear relationships between fish species compositional differences (ζn, number of shared species across any number of watersheds compared) and human pressure, environmental, and geospatial differences among all watersheds and within low, mid‐, and high elevation clusters. A cumulative effect metric was calculated as the sum of response values generated by the model for each human pressure variable specific to each watershed, when evaluated for ζ2 (equivalent to pairwise beta diversity). This metric was tested against the local contribution of each watershed to beta diversity to determine whether watersheds with unique communities had low cumulative effects and are, therefore, candidates for conservation and conversely, whether watersheds with non‐distinctive communities had high cumulative effects and warrant restoration. Species contributions to beta diversity were also assessed across the basin.ResultsZeta diversity across low elevation watersheds indicated stronger filtering by human pressures than mid‐ and high elevation watersheds, which showed more stochastic community assembly. The relative importance and response to human pressures varied based on the diversity component (i.e., total diversity including compositional nestedness vs. turnover) and order of zeta (number of watersheds compared). Cumulative effects were negatively related to community uniqueness, supporting the use of these metrics for developing management priorities.Main ConclusionsThis assessment contributes to biodiversity conservation efforts by identifying important watersheds, species, and human pressures to manage as well as providing a cumulative effect metric directly based on biodiversity responses.

Perils of life on the edge: Climatic threats to global diversity patterns of wetland macroinvertebrates

Climate change is rapidly driving global biodiversity declines. How wetland macroinvertebrate assemblages are responding is unclear, a concern given their vital function in these ecosystems. Using a data set from 769 minimally impacted depressional wetlands across the globe (467 temporary and 302 permanent), we evaluated how temperature and precipitation (average, range, variability) affects the richness and beta diversity of 144 macroinvertebrate families. To test the effects of climatic predictors on macroinvertebrate diversity, we fitted generalized additive mixed-effects models (GAMM) for family richness and generalized dissimilarity models (GDMs) for total beta diversity. We found non-linear relationships between family richness, beta diversity, and climate. Maximum temperature was the main climatic driver of wetland macroinvertebrate richness and beta diversity, but precipitation seasonality was also important. Assemblage responses to climatic variables also depended on wetland water permanency. Permanent wetlands from warmer regions had higher family richness than temporary wetlands. Interestingly, wetlands in cooler and dry-warm regions had the lowest taxonomic richness, but both kinds of wetlands supported unique assemblages. Our study suggests that climate change will have multiple effects on wetlands and their macroinvertebrate diversity, mostly via increases in maximum temperature, but also through changes in patterns of precipitation. The most vulnerable wetlands to climate change are likely those located in warm-dry regions, where entire macroinvertebrate assemblages would be extirpated. Montane and high-latitude wetlands (i.e., cooler regions) are also vulnerable to climate change, but we do not expect entire extirpations at the family level.

Assemblage reorganization of South African dragonflies due to climate change

AbstractAimClimate change is expected to cause large shifts in species assemblages such as dragonflies and damselflies (Insecta: Odonata). Here, we assess the influence of environmental drivers of turnover on Odonata assemblages. Secondly, we map the predicted spatial variation in species composition, first as a gradient of assemblage similarity, and then as discrete bioregions delineating major areas of odonate endemism. Finally, we map the magnitude of expected change in species turnover in response to climate change under two emission scenarios.LocationSouth Africa.MethodsWe used a spatial database comprising of 164 species of odonates and 20 covariates, to explore changes in compositional turnover using generalized dissimilarity models. Bioregions were compiled through various clustering techniques.ResultsPresent‐day odonate bioregions correspond to climatic zones and are clearly separated by transitional zones with rapid spatial turnover. Present odonate bioregions are projected to undergo extensive reorganization by 2050 and 2070. Temporal turnover in species composition is expected to reach up to 80% in the large arid interior and 64% along the coast. Half of all South Africa's protected areas are likely to experience climate induced changes to dragonfly bioregions in the near future.Main conclusionsSpecies assemblages are rapidly changing. This work highlights future shifts in climate will result in complex and nonlinear responses in Odonata communities. With ongoing climate change, current odonate bioregions are predicted to expand while others will contract considerably in size within the next 30 years. The current demarcated protected areas may be inadequate to protect dragonflies as climates change. Odonata can be used to track forefronts of climate change, which will likely affect a larger array of taxa as well.

Understanding the local drivers of beta‐diversity patterns under climate change: The case of seaweed communities in Galicia, North West of the Iberian Peninsula

AbstractAimTo understand spatial‐temporal changes (beta‐diversity) in coastal communities and their drivers in the context of climate change. Coastal ecosystems are extremely exposed and dynamic, where changes in seaweed assemblages have been associated with changing water temperatures. However, at local scale, the effects of changes in the upwelling events and related stressors seek further exploration.LocationGalicia rías, North West of the Iberian Peninsula.MethodsUsing data collected in 42 sampling localities in Galicia rias and over two time periods (1998 and 2014), we analysed changes in the seaweed community's composition through time and space. We calculated the temporal beta‐diversity index and spatial beta‐diversity as the pairwise composition differences between sampling localities. We use generalized dissimilarity models, to identify local environmental drivers of spatial and temporal beta‐diversity.ResultsWe found a significant change in seaweed communities of Galicia rias, between 1998 and 2014 (temporal beta‐diversity). They were mostly related to species loss rather than to species replacement. The dissimilarity among localities (spatial beta‐diversity) was significantly higher in 2014 than in 1998. Nitrate concentration was consistently predicted as the main driver of both temporal and spatial beta‐diversity patterns.Main conclusionsUnlike other studies in marine ecosystems, our results suggest that observed changes in the structure of perennial seaweed assemblages in Galicia Rias might lead to a local biotic heterogenization, indirectly linked to climate change through changes in nutrients availability and the upwelling intensity. Changes in Galicia seaweed communities call scientific attention to the importance of local stressors in climate change studies.

The influence of climate and palaeoclimate on distributions of global conifer clades depends on geographical range size

AbstractAimWe investigate how plant distributions are shaped by current and palaeoclimate regimes. We specifically use global conifer biodiversity to test if palaeoclimatic signatures are stronger in range‐restricted taxa relative to widespread taxa.LocationGlobal.TaxonConiferales.MethodsWe combine global geographical occurrences for 606 conifer species and 69 conifer genera with climate information (modern day and palaeoclimate) to examine the predictors of current conifer distribution. We test how climate predicts the richness of range‐restricted taxa and influences turnover of widespread taxa using generalized dissimilarity models and a zeta diversity framework. We also construct ensemble distribution models to test if palaeoclimates differentially influence the current distribution of range‐restricted versus widespread taxa.ResultsGeneralized dissimilarity models suggest that palaeoclimatic variation is associated with richness differences among small‐range species and genera; specifically, most occur in areas with little temporal climatic variation. Turnover among more widespread taxa, in contrast, is more strongly related to broad modern and palaeoclimatic temperature gradients. Ensemble distribution models also suggest that palaeoclimatic variation contributes more to the current range of genera with restricted ranges.Main conclusionsThe most widespread conifers broadly follow past and current temperature gradients, leading to latitudinal sorting of genera based on their physiological adaptations. Range‐restricted species and genera, however, preferentially occur in climatically stable regions where they contribute to richness hotspots. History, rather than current climate patterns, likely exerts a disproportionate influence on global richness patterns in the group.

What is the role of topographic heterogeneity and climate on the distribution and conservation of vascular epiphytes in the Brazilian Atlantic Forest?

Mapping diversity patterns is important to clarify its causes and is essential information for conservation policies. We map the distribution of vascular epiphytes from the Southern block of the Brazilian Atlantic Forest (SBAF) to understand the main factors responsible for the richness and species turnover, as well as to generate information for the conservation of this functional group. We gathered a data set of vascular epiphytes, mapping the richness and weighted endemism using cells of 0.5° × 0.5°, and performed two Generalized Dissimilarity Models (GDM) using a filter of 18 and 54 species in cells of 5 km × 5 km to evaluate the species turnover and correlation with the climatic and topographic factors. We found four sites presenting both a high richness and endemism. A gradient of richness and species turnover between the coastal and inland regions was confirmed, as well as between the lowlands and the mountainous regions. The main predictors obtained from GDM were geographic distance, cloud cover, and temperature seasonality. The topographic heterogeneity and the resulting climate changes are responsible to enhance the richness and species turnover of vascular epiphytes in the SBAF. It is important to conserve the coastal areas and the mountainous gradients due to the high richness and strong species turnover, but also the inland areas since their composition is quite distinct from previous environments.

Post‐glacial determinants of regional species pools in alpine grasslands

AbstractAimAlpine habitats support unique biodiversity confined to high‐elevation areas in the current interglacial. Plant diversity in these habitats may respond to area, environment, connectivity and isolation, yet these factors have been rarely evaluated in concert. Here we investigate major determinants of regional species pools in alpine grasslands, and the responses of their constituent species groups.LocationEuropean mountains below 50° N.Time periodBetween 1928 and 2019.Major taxa studiedVascular plants.MethodsWe compiled species pools from alpine grasslands in 23 regions, including 794 alpine species and 2,094 non‐alpines. We used species–area relationships to test the influence of the extent of alpine areas on regional richness, and mixed‐effects models to compare the effects of 12 spatial and environmental predictors. Variation in species composition was addressed by generalized dissimilarity models and by a coefficient of dispersal direction to assess historical links among regions.ResultsPool sizes were partially explained by current alpine areas, but the other predictors largely contributed to regional differences. The number of alpine species was influenced by area, calcareous bedrock, topographic heterogeneity and regional isolation, while non‐alpines responded better to connectivity and climate. Regional dissimilarity of alpine species was explained by isolation and precipitation, but non‐alpines only responded to isolation. Past dispersal routes were correlated with latitude, with alpine species showing stronger connections among regions.Main conclusionsBesides area effects, edaphic, topographic and spatio‐temporal determinants are important to understand the organization of regional species pools in alpine habitats. The number of alpine species is especially linked to refugia and isolation, but their composition is explained by past dispersal and post‐glacial environmental filtering, while non‐alpines are generally influenced by regional floras. New research on the dynamics of alpine biodiversity should contextualize the determinants of regional species pools and the responses of species with different ecological profiles.

Zooplankton taxonomic and functional structure is determined by macrophytes and fish predation in a Neotropical river

Habitat structure and predation are major factors that influence the distribution of zooplankton species and functional traits. Here, we analyzed how the structure provided by macrophytes (richness, Shannon’s diversity, and biomass) and potential predation by small-bodied fishes (richness and abundance) determine the richness of species and functional traits of zooplankton, as well as the spatial dissimilarity (beta-diversity) of species and traits. Zooplankton, fish, and macrophytes were simultaneously sampled across a gradient of 30 multi-species macrophyte beds. We assessed spatial patterns of zooplankton under taxonomic and functional approaches, using linear regression models, Generalized Dissimilarity Models, a Structural Equation Model, and a Fourth-Corner Analysis. Zooplankton taxonomic beta-diversity was most represented by the turnover component and zooplankton functional beta-diversity by nestedness. Zooplankton taxonomic richness and taxonomic beta-diversity were positively related to macrophyte biomass, richness, and Shannon’s diversity, whereas zooplankton functional richness and functional beta-diversity were positively related to fish richness and abundance. Macrophyte biomass and diversity oppositely influenced fish structure, which had influence on zooplankton structure. Macrophytes also negatively influenced the zooplankton traits such as body size, reproduction type, habitat, lifespan, and predatory escape response and positively influenced the trait feeding type. Fish were negatively related to the trait body size. The spatial structure generated by macrophyte beds and fish community determined the distribution of zooplankton species and functional traits.