Global Ecology and Biogeography

Biogeography has a critical influence on how ecological communities respond to threats and how effective conservation interventions are designed. For example, the resilience of ecological communities is linked to environmental and climatic features, and the nature of threats impacting ecosystems also varies geographically. Understanding community-level threat responses may be most accurate at fine spatial scales, however collecting detailed ecological data at such a high resolution would be prohibitively resource intensive. In this study, we aim to find the spatial scale that could best capture variation in community-level threat responses whilst keeping data collection requirements feasible. Using a database of biodiversity records with extensive global coverage, we modelled species richness and total abundance (the responses) across land-use types (reflecting threats), considering three different spatial scales: biomes, biogeographical realms, and regional biomes (the interaction between realm and biome). We then modelled data from three highly sampled biomes separately to ask how responses to threat differ between regional biomes and taxonomic group. We found strong support for regional biomes in explaining variation in species richness and total abundance compared to biomes or realms alone. Our biome case studies demonstrate that there is a high variation in magnitude and direction of threat responses across both regional biomes and taxonomic group, but all groups in tropical forest showed a consistently negative response, whilst many taxon-regional biome groups showed no clear response to threat in temperate forest and tropical grassland. Our results suggest that the taxon-regional biome unit has potential as a reasonable spatial and ecological scale for understanding how ecological communities respond to threats and designing effective conservation interventions to bend the curve on biodiversity loss.

AimRapoports rule posits that species range size increases with distance from benign conditions along environmental gradients. We asked whether, and along which axis, marine species obey Rapoports rule when ranges are quantified in three dimensions. LocationGlobal ocean. Taxon> 20,000 marine species spanning pelagic and benthic habitats across major animal phyla and fishes. MethodsWe combined AquaMaps 2.0 / AquaX modelled distributions with independently curated depth limits from FishBase and SeaLifeBase to estimate latitudinal and vertical (bathymetric) ranges for each species. We quantified latitudinal range versus absolute mid-latitude and depth range versus mid-depth, and repeated analyses by habitat and taxonomic group. We used linear and polynomial regressions and Gaussian mixture models in range-gradient space to identify and compare alternative Rapoport regimes. ResultsMarine biodiversity exhibits a classic latitudinal diversity gradient and strong concentration of richness in the upper ocean, with broader ranges at higher latitudes and greater depths. Support for Rapoports rule is weak and inconsistent for latitudinal ranges, but strong and pervasive with depth, with correlations between vertical range and mid-depth frequently exceeding 0.8 across habitats and taxa. Latitudinal and vertical ranges are positively, but only moderately, coupled, with a small subset of "3-D generalists" spanning both large latitudinal and depth extents. Main conclusionsThe marine realm appears to obey Rapoports rule primarily along the vertical, rather than latitudinal, axis. Depth-structured environmental tolerance thus emerges as a dominant constraint on marine range limits and three-dimensional biodiversity gradients.

Climate is a strong predictor of global species richness, but the effects of climatic conditions are difficult to separate from the geography of the climates themselves. Recent work in climate space has shown that the area and isolation of discrete climatic conditions explain broad-scale richness gradients, yet the internal spatial cohesion of those climates remains poorly characterized. Here, we introduce climate percolation as a complementary descriptor of climate geography, measuring the degree to which the total area of a climate bin is concentrated within effectively connected fragments. Using global range maps for amphibians, birds, mammals and reptiles, we quantified species richness across a two-dimensional climate space defined from 12 climatic variables and evaluated the independent and joint effects of climate area, climate isolation and climate percolation across multiple climate-space resolutions. Climate isolation and percolation were strongly coupled: their first joint axis explained, on average, more than 95% of their shared variation, revealing a dominant gradient of climate fragmentation along which geographically isolated climates are also internally subdivided. Despite this collinearity, percolation consistently outperformed isolation in cross-validation across all four vertebrate groups, with particularly strong predictive gains for birds and mammals. The largest improvements, however, came from the shared isolation-percolation axis, indicating that vertebrate richness in climate space is more strongly associated with the integrated geographical structure of climates than with either inter-fragment distance or internal cohesion alone. These results suggest that climate fragmentation is a multidimensional property of environmental space, combining both the distance among climate fragments and the dominance structure of connected areas. By extending climate-space approaches from area and isolation to percolation, our framework provides a more complete description of how the geography of climate may shape global richness gradients and offers a structural basis for anticipating how future changes in climate connectivity could alter biodiversity patterns.

The extinction rates of Anthropocene biodiversity vary dramatically through geographic and phylogenetic space, with certain regions and lineages concentrating high defaunation rates, while others remain nearly unchanged. This heterogeneity results from (spatial and phylogenetic) variation in the interactions between species fitness-relevant traits and environmental threats that trigger the pathway to extinction. Existing evidence reveals that factors including life histories, ecophysiology, and resource-use generalism influence variation in species declines under rapidly changing environments. An emerging hypothesis predicts that species spread across different locations of the 24h diel spectrum are exposed to different anthropogenic pressures on demographic stability (e.g. daytime contact with humans), which can trigger differential extinction risk among diurnal, nocturnal and cathemeral (day-night actives) species. However, this prediction remains largely neglected. Only a single large-scale test of this hypothesis, on mammals, exists, which documented higher declines in diurnal species, driven by primates. Here, we address this hypothesis across the worlds tetrapods, spanning >23,000 species across both endotherms and ectotherms for the first time. Our results reveal that extinction risk is higher across diurnal species from tropical regions with greater human footprint. Collectively, extinction risk is the synergistic outcome of the interplay between extrinsic human-induced pressures and species traits.

Species abundance is expected to decrease from the centre towards the edge of their ecological niches (abundant niche-centre hypothesis). Recently, Osorio-Olvera et al. (2020) reported strong support for the abundant niche-centre relationship in North American birds. We demonstrate here that methodological decisions strongly affected perceived support. Avoiding these issues casts doubt on conclusions by Osorio-Olvera et al. and the putative support for the abundant nichecentre hypothesis in North American birds.

Many species are responding to global warming by shifting their distributions upslope to higher elevations, but the observed rates of shifts vary considerably among studies. Here we test the hypothesis that this variation is in part explained by latitude, with tropical species being generally more responsive to warming temperatures than are temperate species. We find support for this hypothesis in each of two independent empirical datasets--shifts in species elevational ranges, and changes in composition of forest inventory tree plots. Tropical species are tracking rising temperatures 2.1-2.4 times (range shift dataset) and 10 times (tree plot dataset) better than their temperate counterparts. Models predict that for a 100 m upslope shift in temperature isotherm, species at the equator have shifted their elevational ranges 93-96 m upslope, while species at 45{degrees} latitude have shifted only 37-42 m upslope. For tree plots, models predict that a 1{degrees}C increase in temperature leads to an increase in community temperature index (CTI), a metric of the average temperature optima of tree species within a plot, of 0.56 {degrees}C at the equator but no change in CTI at 45{degrees} latitude (-0.033). This latitudinal gradient in temperature tracking suggests that tropical montane biotas may be on an "escalator to extinction" as global temperatures continue to rise.

Introduction and AimAssessing the realized climate limits for a species based on the climate conditions (i.e., different aspects of temperature and precipitation) a species has experienced over its range enables us to determine the climatic boundaries of its existence, and thus its potential exposure to novel climate conditions in the future. We combine species range maps from IUCN and BirdLife International with global climate data from the ERA5 reanalysis and five Earth System Models (ESMs) to produce ClimLimits: a database of multivariate realized species climate limits based on historical temperature and precipitation for terrestrial and freshwater animal species worldwide. Main variables includedFor a total of 54,255 species (24,731 terrestrial, 18,182 freshwater, and 11,342 terrestrial-freshwater species), we estimated 44 species climate limits, which delineate the most extreme climate conditions experienced by a species over its entire range over the last 80 years (1940-2020). The database accounts for three aspects of species climate limits: a) maximum and minimum values of temperature and precipitation experienced over the historical reference period, b) maximum annual variability in temperature and precipitation, and c) maximum frequency, intensity, duration and severity of extreme events (heatwaves, cold-spells, and droughts). Climate data is sourced from the ERA5 reanalysis and from five different Earth System Models (ESMs), producing 6 different subsets of the ClimLimits database. Time coverageSpecies climate limits are estimated based on historical climate records from 1941-2014 (5 ESMs) and 1940-2020 (ERA5). Temperature-based limits are inferred at a daily scale, while precipitation-based limits are inferred at a monthly and yearly scale. Spatial coverageGlobal, over 24km x 24km grid-cells. TaxaTerrestrial and freshwater taxa, including amphibians, birds, mammals, reptiles, freshwater fish, and freshwater invertebrates, with shapefiles from IUCN and BirdLife International. Data is produced at the species level. ApplicationsClimLimits provides ready-to-use standardized realized climate limits for individual species across multiple aspects of climate, facilitating global-scale assessments of macroecological patterns and climate exposure risk for species.

The development of deep learning methods using convolutional neural networks (CNNs) has revolutionised the field of computer vision in recent years. The automation of taxonomic identification using CNNs leads naturally to the use of such technology for rapidly generating large organismal datasets in order to study the evolutionary and ecological dynamics of biological communities across time and space. While CNNs have been used to train machine learning classifiers that can identify organisms to the species level for several groups, this vision of automated community ecology has yet to be thoroughly tested or fulfilled. Here, we present a case study of automated community ecology using a large dataset of Atlantic planktonic foraminifera for which the generation of species labels and morphometric measurements was completely automated. We compare standard community diversity metrics between the fully automated dataset and a "traditional" dataset with human-identified specimens. We show that there is high congruence between the results, and that machine classifications help avoid biases that can result in the inference of misleading biodiversity patterns. Our study demonstrates the viability and potential of fully automated community ecology and sets the stage for a new era of ecological and evolutionary inquiry driven by artificial intelligence.

AimWe examined the patterns and processes of taxonomic and functional dissimilarities for two disparate organismal groups (ectothermic hawkmoths and endothermic birds) across a broad tropical elevational gradient. LocationEaglenest Wildlife Sanctuary (northeast India), eastern Himalayan global biodiversity hotspot. Taxon4,731 hawkmoths; 15,387 birds MethodsTurnover and nestedness components for taxonomic and functional dissimilarities were obtained using the methods developed by Baselga (2013) and Leprieur et al., 2012. We used Generalized Dissimilarity Modeling (GDM) with geographic distance, contemporary and historic climatic variables to assess the relative importance of dispersal and environmental processes in determining the beta diversity. Functional redundancy (FRed) was calculated for both organismal groups using the Simpsons diversity indices. Null modeling was used to determine randomness in species and trait distributions. ResultsTurnover dominated taxonomic and functional dissimilarities, however the contribution of nestedness was considerably higher to the latter. Overall, the rate of dissimilarity with distance, for both facets of diversity, was significantly higher for birds, with stronger contributions of geographic distance and historic climate; whereas the hawkmoth dissimilarities were strongly correlated with only contemporary climate. Taxonomic dissimilarities deviated significantly from null, whereas functional dissimilarities exhibited high redundancy and randomness. Main ConclusionsOverall, our results suggest that while the drivers of beta-diversity exhibit idiosyncrasy and taxon-specificity; for a given taxa, they are consistent across the two facets of dissimilarity. More importantly, regardless of the principal predictor, the net result was that of high taxonomic turnover, which is de-coupled to a high degree from functional turnover in these tropical ecosystems. The large redundancy in trait values, despite high species turnover, indicates functional resilience of these tropical communities. The consistency of this pattern, across two disparate organismal groups, is suggestive of a key mechanism in which tropical communities may retain functionality of ecosystems in a changing environment.

As humans increasingly modify the natural world, many animals have responded by changing their behaviour. Predicting the extent of these responses is a key step in conserving these species. For example, the tendency for some species of birds to incorporate anthropogenic items - particularly plastic material - into their nests is of increasing concern, as in some cases this behaviour has harmful effects on both adults and young. Studies of this phenomenon, however, have to date been limited in geographic and taxonomic scope. To investigate the global correlates of anthropogenic (including plastic) nest material use, we used Bayesian phylogenetic mixed models and a dataset of recorded nest materials in 6,147 species of birds. We find that after controlling for research effort, anthropogenic nest material use is correlated with proximity to human landscape modification, synanthropic (artificial) nesting locations, breeding environment, and the number of materials that has been recorded within the species nest. We also demonstrate that anthropogenic nest material use is unrelated to body mass, range size, or conservation status. These results indicate that anthropogenic materials are more likely to be included in nests when they are more readily available, as well as potentially by species who have more flexibility in nest material choice.

AimTo examine the support of two ecological diversity theories- The Ecological Limits Hypothesis (ELH) and the Niche Conservatism Hypothesis (NCH) - in explaining patterns of global shark diversity. LocationGlobal scale and two ecological realms: the Tropical Atlantic and the Central Indo-Pacific. Time PeriodPast 100 years Major Taxa StudiedWe examined 534 species of sharks and chimaeras, and we performed two subclade analyses on 272 species of ground sharks and 15 species of mackerel sharks. MethodsWe compared the species richness, mean root distance (MRD), and tree imbalance patterns to those simulated under the ELH and NCH with temperate and tropical centers of origin. We used sea temperature as a proxy for energy availability. We examined the importance of biogeographic history by comparing the model fits between two taxonomic groups, ground and mackerel sharks, and two geographic regions, the Tropical Atlantic realm and Central Indo-Pacific realm. ResultsThe ELH, temperate-origin model had the best fit to the global dataset and the sub-analyses on ground sharks, mackerel sharks, and the Tropical Atlantic. The NCH temperate-origin model provided the best fit for the Central Indo-Pacific. The {beta} metric of tree symmetry showed the best potential for differentiating between the ELH and NCH models, and the correlation coefficient for temperature vs MRD performed the best at differentiating between temperate and tropical origin of ancestors. Main ConclusionsThe global and subclade analyses indicate the ELH provides the best explanation for global scale shark diversity gradients even in clades with varying ecology. However, at the realm scale, biogeographic history has an impact on richness patterns. Comparing multiple metrics in relation to a simulation model provides a more rigorous comparison of these models than simple regression fits.

O_LIGlobal warming is pushing species to shift their ranges towards higher latitudes and elevations, causing a reassembly of plant communities potentially accompanied by community thermophilization (i.e., an increasing number or cover of thermophilic species, sometimes at the expense of mesic or cold-adapted species). Given the large variation typically observed in the magnitude and direction of range shifts, quantifying community thermophilization might provide a sensitive method to detect range shifts within short time periods and across limited spatial extents. Assessing changes in plant community composition as a whole might integrate early signs of range shifts across co-occurring species while accounting for changes in both occurrence and abundance. C_LIO_LIHere, we combine an assessment of (i) species-level range shifts, (ii) changes in species richness and (iii) changes in community-inferred temperatures along three mountain roads in Switzerland to ask whether plant communities have responded to warming climate over a 10 year period, and whether community thermophilization is an appropriate metric for early detection of these changes. C_LIO_LIWe found a community thermophilization signal of +0.13{degrees}C over the 10-year study period based on presence-absence data only. Despite significant upward shifts of species upper range limits in the lower part of the studied elevational gradient and a decrease in species richness at high elevations, significant thermophilization was not detectable if community- inferred temperatures were weighted by species covers. Low cover values of species that were gained or lost over the study period and their similar species-specific temperatures to resident species explained the discrepancy between the thermophilization detected in either cover-weighted or unweighted models. C_LIO_LISynthesis. Our work shows that plant species are shifting to higher elevations along roadsides in the western Swiss Alps and that this translates into a detectable warming signal of plant communities within 10 years. However, the species-level range shifts and the community-level warming effect are mostly based on low cover values of gained/lost species, preventing the detection of community thermophilization signals when incorporating cover changes. We therefore recommend using unweighted approaches for early detection of community-level responses to changing climate, ideally set into context by also assessing species-level range shifts. C_LI

AimThe Global Biodiversity Information Facility (GBIF) is the most prominent source of species occurrence data for modeling climate niches, but exhibits strong unevenness in its data coverage across different geographic regions. The impact of this spatial bias on the reliability of GBIF-based plant climate niches in Europe remains unexplored. This study aims to address this gap, and to investigate whether the targeted integration of additional atlas data can reduce the potential impact of the spatial bias. LocationEurope. Time period1950s - 2024 Major taxa studiedEuropean grassland plant species. MethodsWe analyzed the climate niches of a large number of grassland species, with diverse distribution patterns across Europe, based on a) GBIF and b) on an enriched version of GBIF with national atlas data from Eastern European countries (GBIF+), where data coverage is currently low in GBIF. We followed best practices in niche characterization, particularly by performing environmental subsampling. The accuracy in climate niche properties was determined by comparing niches based on GBIF and GBIF+ data with niches based on a careful implementation of expert range maps as reference dataset. We focused on niche optimum position and niche similarity. Additionally, we investigated how biogeographical indicators can predict variability in climate niche accuracy. ResultsMost species exhibited reliable climate niche characterization using GBIF data, especially for widely distributed species. Yet, reliability decreased with continentality; that is, when species were primarily distributed in Eastern Europe. Integrating additional data did not significantly reduce this bias in niche characterization. Main conclusionsDespite the spatial bias in its records, GBIF can be used to reliably characterize the climate niches of many species in Europe if uneven sampling effort is accounted for. The laborious integration of additional data to address spatial bias does not yield the desired increase in niche reliability.

O_LIClimate change and other anthropogenic drivers of biodiversity change are unequally distributed across the world. The geographic patterns of different drivers, and the spatial overlap among these drivers, have important implications for the direction and pace of biodiversity change, yet are not well documented. Moreover, it is unknown if the geographic patterns of drivers differ between the terrestrial and marine realm, as expected due to marked differences in how humans interact with the land and ocean. C_LIO_LIWe compiled global gridded datasets on climate change, land-use, resource exploitation, pollution, species invasions, and human population density. We used multivariate statistics to examine the spatial relationships among the datasets and to characterize the typical combinations of drivers experienced by different parts of the world. C_LIO_LIWe found stronger positive correlations among drivers in the terrestrial than in the marine realm, leading to areas of high intensities of multiple drivers on land. Climate change tended to be negatively correlated with other drivers in the terrestrial realm (e.g., in the tundra and boreal forest with high climate change but low human use and pollution) whereas the opposite was true in the marine realm (e.g., in the Indo-Pacific with high climate change and high fishing). C_LIO_LIWe show that different regions of the world can be defined by anthropogenic threat complexes (ATCs), distinguished by different sets of drivers with varying intensities. The ATCs can be used to test hypothesis about the pattern of biodiversity change, especially the joint effects of multiple drivers. More generally, our global analysis highlights the broad conservation priorities needed to mitigate the effects of anthropogenic change on biodiversity responses, with different priorities emerging on land and in the ocean, and in different parts of the world. C_LI

AimThe assembly of montane plant communities through time is underlain by historical and abiotic factors. However, the extent of evolutionary connectivity between ancient highland ecosystems and surrounding lowlands remains unclear. Here, we investigate the evolutionary connections between the campos rupestres, a hyperdiverse and fragmented montane vegetation complex in eastern South America, and lowland biomes surrounding it: savannas, rainforests, and seasonally dry tropical forests. LocationEastern South America. Time periodCenozoic. Major taxa studiedFlowering plants. MethodsUsing phylogenetic beta diversity analyses for 13 angiosperm clades, we assess the degree of lineage dissimilarity between campos rupestres subregions and adjacent biomes. We also apply generalized dissimilarity modeling to determine the role of climate, soil, and geographic distance in shaping spatial patterns of phylogenetic composition. ResultsOur results reveal high lineage permeability between campos rupestres and surrounding biomes, with lineage sharing largely reflecting biome adjacency. This pattern is mainly driven by shared climatic conditions, which are the strongest predictors of phylogenetic dissimilarity. Main conclusionsWe highlight the importance of lineage exchange between lowland and montane environments for the assembly of highland floras. By showing that lineage movements across biome boundaries have been common over time and spatial scales, our study challenges the idea that ancient Neotropical mountains are isolated sky-islands. Instead, we emphasize the dynamic nature of montane plant diversity and the pivotal role of climate in shaping evolutionary connections between highlands and lowlands.

A shared goal within macroecology, biogeography and population ecology research is to understand biodiversity patterns and the processes driving them across spatial and taxonomic scales. A common approach to study macroecological patterns and processes involves developing and testing ecogeographical rules or hypotheses. The much-debated abundant-centre hypothesis posits that species abundances are highest in their range centres and decline towards their range edges. We perform the largest global test of the hypothesis to date, on 3,675 species, using 6,055,549 abundance observations. Using meta-analytical approaches, we summarised species-level abundance-distance correlations exploring the effects of dispersal-related species traits on abundance-distance relationships. Overall, animals did not follow abundant-centre patterns, whereas plants tended to. Larger-bodied mammals were more likely to conform to abundant-centre patterns, as were mammals and freshwater fishes from higher latitudes. Perennial life cycles and large range sizes were significant predictors of abundant-centre patterns in plants. Trees and shrubs with larger seeds showed more support for abundant-centre patterns. Accounting for species dispersal improves models of abundant-centre patterns across geographic space. Assuming abundant-centre patterns represent optimal equilibria within nature, our findings suggest that abundant-centre relationships are not a general ecological phenomenon but tend to manifest only in species with higher dispersal capabilities.

AimBiodiversity is distributed unevenly among lineages and regions, and understanding the processes generating these global patterns is a central goal in evolutionary research, particularly in light of the current biodiversity crisis. Here, we integrate phylogenetic relatedness with species diversity patterns in four major clades of living tetrapods (amphibians, squamates, birds, and mammals) to approach this challenge. LocationGlobal. Time period300 million years ago - Present. Major taxa studiedTetrapods. MethodsWe studied geographic patterns of richness-corrected phylogenetic diversity (residual PD), identifying regions where species are phylogenetically more closely or distantly related than expected by richness. We explored the effect of different factors in residual PD: recent speciation rates, temporal trends of lineage accumulation, and environmental variables. Specifically, we searched for evolutionary and ecological differences between regions of high and low residual PD. ResultsOur results show heterogeneous spatial patterns of diversity dynamics across tetrapods. They reveal an overall negative relationship between recent speciation rates and residual PD, underscoring the role of recent speciation events in structuring current biogeographic patterns. Furthermore, we found differences between endothermic and ectothermic tetrapods in response to temperature and precipitation, highlighting the pivotal role of thermal physiology in shaping diversity dynamics. Main conclusionsGeographic patterns of diversity dynamics are heterogeneous across tetrapod clades and help us disentangle the evolutionary and ecological processes underlying them. By illuminating the multifaceted factors underpinning global diversity patterns, our study represents a significant advancement towards better understanding of how the present-day diversity of tetrapods was formed and how speciation rates influenced their species and phylogenetic diversity across clades and regions.

Arid environments constitute one of the main terrestrial biomes on Earth and are predicted to expand under ongoing climate change. Studying the effect of arid conditions on biodiversity patterns and ecological dynamics is therefore critical to understand the evolutionary fate of desert-adapted faunas. Here we provide a global assessment of how aridity influences climatic niche breadth and phylogenetic structure across terrestrial vertebrates. Using distributional data for over 34,000 species of amphibians, squamates, birds, and mammals, combined with environmental data and nearly complete phylogenies of these clades, we quantified species positions along aridity gradients and their climatic niche breadth, and evaluated phylogenetic clustering at multiple spatial scales. Across all groups, species occupying more arid environments exhibited significantly narrower climatic niches than those from non-arid habitats, supporting the hypothesis that ecological filtering in deserts promotes climatic specialization. Further, analyses of system-wide community phylogenetic structure revealed significant phylogenetic clustering in most arid systems for all clades except birds, underscoring that deserts broadly act as ecological filters at large scale, but this effect is subjected to clade-specific traits. However, finer-scale analyses showed significant phylogenetic overdispersion in several cases, suggesting that competition and micro-niche dynamics might be stronger determinants of phylogenetic structure at the local-to-regional level. Together, our results demonstrate that drylands act as ecological filters shaping both functional and evolutionary dimensions of biodiversity, with implications for predicting biotic responses to desertification and climate change.

Anthropogenic climate and land-use change are driving an emerging extinction crisis that is expected to intensify in the future. Species climatic niche limits shape their sensitivity to these pressures, potentially leading to disproportionate extinction risk among more climatically vulnerable species. We test whether realized climatic niche limits are associated with current and projected extinction risk across >23,000 terrestrial vertebrate species. We assessed the phylogenetic structure of thermal and aridity niche limits and related them to IUCN threat status and simulated future extinctions. We show that realized niche limits are phylogenetically conserved, indicating evolutionary clustering of climatic tolerances. Species with colder upper thermal limits were more likely to be classified as threatened across taxa. Aridity niche limits show weaker and less consistent relationships with current threat status. Simulated extinction scenarios reveal taxon-specific patterns of climatic niche loss compared to random species extinctions. We also show significant reductions in phylogenetic diversity relative to randomized expectations based on simulated species extinctions. We find that extinction risk is systematically associated with species climatic niche limits, reflecting evolutionary constraints on environmental tolerance. These results indicate that future extinctions will disproportionately affect climatically vulnerable lineages, with cascading consequences for phylogenetic diversity and ecosystem functioning.

AimDetecting and describing temporal changes in biological communities is fundamental to biodiversity research and applied ecology. Species richness remains a widespread metric in long-term monitoring, yet it obscures underlying processes since changes in species richness are often only the result of turnover, homogenisation and/or shifts in relative abundances. Furthermore, biodiversity trends and their drivers can vary across spatial scales, demanding spatially explicit approaches. This study aims at unravelling how changes in community structure shape trends in richness across spatial scales, offering a more mechanistic view on biodiversity trend detection. LocationEurope Time period1975 - 2023 Major taxa studiedBirds MethodsWe first assessed trends in breeding bird richness on local (site-level) and national scale for 25 European countries or sub-divisions using linear models. Next, we applied the multi-scale Measures of Biodiversity (MoB) framework in a temporal context to decompose changes in species richness into contributions from individual density, species-abundance distribution, and con-specific spatial aggregation. We then quantify how these components drive species richness from local plots to national extents. Analyses were further conducted separately for farmland and forest guilds, as well as across ecoregions. ResultsThree general patterns emerged beyond variation among countries and functional guilds: Aggregation dominates local richness dynamics, evenness governs broad-scale trends, and density plays an intermediate role. Findings of distinct local and national trends in bird richness agree with previous findings, albeit we find more heterogeneous average trends among countries on local scales. Distinct trends and components patterns vary among ecoregions within countries, highlighting the need for sub-national analyses. Main conclusionsThis scale-explicit, component-based approach reveals how changes in community structure shape trends in species richness from local to national scales. Such mechanistic insights of biodiversity change might enable more precisely targeted conservation strategies and identification of external drivers.