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Aim: Life in mountains is associated with multiple features that increase the risk of demographic collapses in populations – small geographic ranges, short breeding seasons, specialization to harsh climates – leading to the hypothesis that extinction risk is exacerbated in species inhabiting higher elevations. Here, we implement the first test of this hypothesis across the amphibian tree of life – the tetrapods with the largest proportion of montane species, and nature's most threatened animals. Location: Global. Time Period: Present. Major Taxa Studied: Class Amphibia. Methods: We collated a dataset spanning 8042 species from across all three amphibian orders (Anura, Caudata and Gymnophiona). We preformed phylogenetic logistic regressions to test the predictions that extinction risk increases with elevation, and whether this effect is caused by factors previously hypothesised to drive high‐elevation declines, including restrictions on species' geographic ranges, variation in their life histories and the presence of infectious disease. Results: Globally, extinction risk increases towards higher elevations. At order‐level, this relationship holds for frogs and salamanders. Even when controlling for geographic range size, life histories and infectious disease, extinction risk increases with elevation for amphibians combined and frogs globally, and in the Americas. In contrast, whereas extinction risk is greater among high‐elevation Eurasian amphibians, this relationship is explained by larger body sizes and lower fecundity. Main Conclusions: Our analyses indicate that after considering factors previously thought to explain the increase in extinction risk towards higher elevations (e.g., geographic range size, disease), elevation remains a significant predictor of amphibian extinction risk. Given that the only available tests of this hypothesis in other tetrapods (birds and reptiles) conflict with our findings, we suggest that physiological or life‐history features of amphibians may explain this observed phenomenon. [ABSTRACT FROM AUTHOR]

The global‐scale decline of animal biodiversity ('defaunation') represents one of the most alarming consequences of human impacts on the planet. The quantification of this extinction crisis has traditionally relied on the use of IUCN Red List conservation categories assigned to each assessed species. This approach reveals that a quarter of the world's animal species are currently threatened with extinction, and ~1% have been declared extinct. However, extinctions are preceded by progressive population declines through time that leave demographic 'footprints' that can alert us about the trajectories of species towards extinction. Therefore, an exclusive focus on IUCN conservation categories, without consideration of dynamic population trends, may underestimate the true extent of the processes of ongoing extinctions across nature. In fact, emerging evidence (e.g. the Living Planet Report), reveals a widespread tendency for sustained demographic declines (an average 69% decline in population abundances) of species globally. Yet, animal species are not only declining. Many species worldwide exhibit stable populations, while others are even thriving. Here, using population trend data for >71,000 animal species spanning all five groups of vertebrates (mammals, birds, reptiles, amphibians and fishes) and insects, we provide a comprehensive global‐scale assessment of the diversity of population trends across species undergoing not only declines, but also population stability and increases. We show a widespread global erosion of species, with 48% undergoing declines, while 49% and 3% of species currently remain stable or are increasing, respectively. Geographically, we reveal an intriguing pattern similar to that of threatened species, whereby declines tend to concentrate around tropical regions, whereas stability and increases show a tendency to expand towards temperate climates. Importantly, we find that for species currently classed by the IUCN Red List as 'non‐threatened', 33% are declining. Critically, in contrast with previous mass extinction events, our assessment shows that the Anthropocene extinction crisis is undergoing a rapid biodiversity imbalance, with levels of declines (a symptom of extinction) greatly exceeding levels of increases (a symptom of ecological expansion and potentially of evolution) for all groups. Our study contributes a further signal indicating that global biodiversity is entering a mass extinction, with ecosystem heterogeneity and functioning, biodiversity persistence, and human well‐being under increasing threat. [ABSTRACT FROM AUTHOR]

Aim: The emergence of large‐scale patterns of animal body size is the central expectation of a wide range of (macro)ecological and evolutionary hypotheses. The drivers shaping these patterns include climate (e.g. Bergmann's rule), resource availability (e.g. 'resource rule'), biogeographic settings and niche partitioning (e.g. adaptive radiation). However, these hypotheses often make opposing predictions about the trajectories of body size evolution. Therefore, whether underlying drivers of body size evolution can be identified remains an open question. Here, we employ the most comprehensive global dataset of body size in amphibians, to address multiple hypotheses that predict patterns of body size evolution based on climatic factors, ecology and biogeographic settings to identify underlying drivers and their generality across lineages. Location: Global. Time Period: Present. Major Taxa Studied: Amphibians. Methods: Using a global dataset spanning 7270 (>87% of) species of Anura, Caudata and Gymnophiona, we employed phylogenetic Bayesian modelling to test the roles of climate, resource availability, insularity, elevation, habitat use and diel activity on body size. Results: Only climate and elevation drive body size patterns, and these processes are order‐specific. Seasonality in precipitation and in temperature predict body size clines in anurans, whereas caecilian body size increases with aridity. However, neither of these drivers explained variation in salamander body size. In both anurans and caecilians, size increases with elevational range and with midpoint elevation in caecilians only. No effects of mean temperature, resource abundance, insularity, time of activity or habitat use were found. Main Conclusions: Precipitation and temperature seasonality are the dominant climatic drivers of body size variation in amphibians overall. Bergmann's rule is consistently rejected, and so are other alternative hypotheses. We suggest that the rationale sustaining existing macroecological rules of body size is unrealistic in amphibians and discuss our findings in the context of the emerging hypothesis that climate change can drive body size shifts. [ABSTRACT FROM AUTHOR]

Marine heatwaves caused by global warming are progressively degrading coral reefs worldwide via the process of coral bleaching – the expulsion of photosynthetic endosymbionts. However, coral bleaching is not spatially homogeneous, but varies across environmental gradients in association with local conditions and taxonomic composition. Emerging evidence suggests that mangrove habitats are recurrent ''microenvironments' for reef corals, providing key biogeochemical services believed to influence their resilience, and housing co‐tolerant coral taxa. This close association between coral reefs and mangroves has led to the hypothesis that the extent of coral bleaching is reduced by the proximity of reef building corals to mangroves. Here, we present the first global‐scale test addressing this hypothesis. Using Bayesian generalised linear mixed effect modelling, we show that coral bleaching tends to increase under higher thermal stress when corals are further away from mangroves. When comparing conditional effects, corals furthest away from mangroves also show the highest levels of bleaching, suggesting a phenomenon of reduced bleaching for corals residing closer to mangroves under thermal stress. The drivers of this pattern may be numerous, but most likely include the presence of co‐tolerant coral species which are known to be associated with mangroves. Future research should focus on disentangling the mechanisms underlying these coral bleaching patterns in association with mangroves, specifically focusing on in‐situ environmental and taxonomic data collection. These endeavours will most likely require high‐resolution analyses of coral reefs at more local‐scales. Ultimately, our findings add to the ever‐growing importance of mangroves for near‐shore coral reef environments, and suggest a potentially important benefit for coral reefs associated with mangroves in the Anthropocene. [ABSTRACT FROM AUTHOR]

Variation in genome size spans multiple orders of magnitude among animals. Despite the longstanding debate regarding the adaptive value or costs of genomic complexity, genome size has been proposed to influence extinction risk under the rapidly changing environments of the Anthropocene.The main hypothesis suggests that genome enlargement increases the accumulation of deleterious mutations while reducing rates of organismal growth and development. These combined effects of larger genome size are predicted to trigger population declines that can lead to extinction, especially under rapidly changing environments that disrupt demographic resilience.Comparative evidence from terrestrial plants and across vertebrates has provided mixed support for this hypothesis. However, large‐scale comparative studies based on explicit phylogenetic approaches remain lacking. Using a global‐scale amphibian dataset and two recognised proxies of extinction risk (International Union for Conservation of Nature IUCN conservation categories and population trends), we test the prediction that genomes are larger (as estimated by C‐value) in species facing extinction risk. We combine these analyses with life‐history traits widely known to be implicated with extinctions (body size, fecundity), along with a range of environmental factors.Our phylogenetic analyses consistently failed to identify an effect of genome size on either of the two proxies for extinction risk. The only consistent predictor of extinction risk observed across models performed for amphibians combined and for orders separately was decreasing geographical range size. We also identified a role for larger body size, decreasing range of environmental temperature (for anurans) and increasing levels of UV‐B radiation (for salamanders) as drivers of increasing threat.Our study provides no support for the prediction that species with larger genomes suffer heightened risk of extinction. We discuss some fundamental limitations underlying the genome size‐extinction hypothesis, and suggest that it is not a promising avenue to elucidate the causes of biodiversity declines in the Anthropocene. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Rising ocean temperatures are the primary driver of coral reef declines throughout the tropics. Such declines include reductions in coral cover that facilitate the monopolization of the benthos by other taxa such as macroalgae, resulting in reduced habitat complexity and biodiversity. Long‐term monitoring projects present rare opportunities to assess how sea surface temperature anomalies (SSTAs) influence changes in the benthic composition of coral reefs across distinct locations. Here, using extensively monitored coral reef sites from Honduras (in the Caribbean Sea), and from the Wakatobi National Park located in the center of the coral triangle of Indonesia, we assess the impact of global warming on coral reef benthic compositions over the period 2012–2019. Bayesian generalized linear mixed effect models revealed increases in the sponge, and hard coral coverage through time, while rubble coverage decreased at the Indonesia location. Conversely, the effect of SSTAs did not predict any changes in benthic coverage. At the Honduras location, algae and soft coral coverage increased through time, while hard coral and rock coverage were decreasing. The effects of SSTA at the Honduras location included increased rock coverage, but reduced sponge coverage, indicating disparate responses between both systems under SSTAs. However, redundancy analyses showed intralocation site variability explained the majority of variance in benthic composition over the course of the study period. Our findings show that SSTAs have differentially influenced the benthic composition between the Honduras and the Indonesian coral reefs surveyed in this study. However, the large intralocation variance that explains the benthic composition at both locations indicates that localized processes have a predominant role in explaining benthic composition over the last decade. The sustained monitoring effort is critical for understanding how these reefs will change in their composition as global temperatures continue to rise through the Anthropocene. [ABSTRACT FROM AUTHOR]

Aim: Rising ocean temperatures are widely recognized as the dominant driver behind the rapid degradation of coral reefs via the process of coral bleaching (the expulsion of photosynthetic endosymbionts, which reveals the coral skeleton). However, bleaching of hard corals is often assumed to be further aggravated by the effect of local‐scale stressors from anthropogenic activity, accelerating coral reef decline where these stressors are stronger. Despite the importance of this hypothesis, the interaction between climate change and local stressors for driving coral bleaching has only been investigated in a handful of studies, with no large scale (regional or global) test conducted thus far. We investigate the impact of human population density (HPD) – a proxy for local stressors – in both protected and non‐protected marine regions, and their interaction under heat stress as drivers of coral bleaching. Location: Global. Time period: 2002–2018. Major taxa studied: Scleractinia corals. Methods: Using 9,170 coral reef surveys worldwide, we performed Bayesian modelling to assess the probability of coral bleaching in response to local‐scale stressors in interaction with global warming. Results: Local HPD does not exacerbate coral bleaching, either independently or under thermal stress from climate change. Rather, the relationship between HPD and temperature stress appears weakly antagonistic for coral bleaching, contradicting the expectation that HPD increases sensitivity of corals to bleaching under thermal stress. Main conclusions: Local HPD does not interact with global warming for degrading coral reefs. However, regional variation in bleaching patterns exists. Consequently, bleaching will continue to occur on most coral reefs globally regardless of local HPD. Thus, it is likely that even isolated, well‐protected, coral reefs will continue to decline because of climate warming‐induced bleaching. Therefore, tackling the source of global warming remains the most effective way to mitigate coral reef decline via coral bleaching. [ABSTRACT FROM AUTHOR]

Aim: Biodiversity is not uniformly distributed across the Earth's surface, even among physiographically comparable biomes in different biogeographic regions. For lizards, the world's large desert regions are characterized by extreme heterogeneity in species richness, spanning some of the most species‐rich (arid Australia) and species‐poor (central Asia) biomes overall. Regional differences in species diversity may arise as a consequence of the interplay of several factors (e.g., evolutionary time, diversification rate, environment), but their relative importance for biogeographic patterns remains poorly known. Here we use distributional and phylogenetic data to assess the evolutionary and ecological drivers of large‐scale variation in desert lizard diversity. Location: Deserts worldwide. Major taxa studied: Lizards (non‐snake squamates). Methods: We specifically test whether diversity patterns are best explained by differences in the ages of arid‐adapted lineages (evolutionary time hypothesis), by regional variation in speciation rate, by geographic area of the arid systems, and by spatial variation related to environment (climate, topography, and productivity). Results: We found no effect of recent speciation rate and geographic area on differences in desert lizard diversity. We demonstrate that the extreme species richness of the Australian deserts cannot be explained by greater evolutionary time, because species began accumulating more recently there than in more species‐poor arid regions. We found limited support for relationships between regional lizard richness and environmental variables, but these effects were inconsistent across deserts, showing a differential role of the environment in shaping the lizard diversity in different arid regions. Main conclusions: Our results provide evidence against several classic hypotheses for interregional variation in species richness, but also highlight the complexity of processes underlying vertebrate community richness in the world's great arid systems. [ABSTRACT FROM AUTHOR]

Aim: Worldwide distribution patterns of living animals are structured in multiple zoogeographical regions, characterized by faunas with homogeneous composition that are separated by sharp boundaries. These zoogeographical regions can differ depending on the considered animal group, probably because they have distinct characteristics such as dispersal, metabolism, or evolutionary history, and thus divergent responses to major biogeographical drivers, such as tectonic movements, abrupt climate transitions and orographic barriers. Here, we tested if the drivers of biogeographical boundaries are different between vertebrate classes with strongly divergent traits and evolutionary history. Location: Global. Time period: Present. Major taxa studied: Amphibians, birds and mammals. Methods: We focused on terrestrial biogeographical boundaries, considering multiple potential drivers: spatial heterogeneity of present‐day climate, altitudinal variation, long‐term tectonic movements and past climate change (temperature). We used spatially explicit regression models and geographically weighted regressions to select and quantify the factors explaining the position of the biogeographical boundaries between vertebrate classes. Results: For mammals, tectonic movements, abrupt climatic transitions and orographic barriers jointly determined extant biogeographical boundaries, with tectonic movements being the most important. For birds, abrupt climatic transitions played the strongest role, while the effect of orographic barriers was weak. For amphibians, biogeographical boundaries mostly corresponded to areas with abrupt climatic transitions. The strongest transitions of amphibian faunas occur in areas with abrupt shifts of temperature and precipitation regimes. Main conclusions: Our analyses confirmed that different drivers have jointly shaped the global vertebrate biogeographical regions, and highlight that taxa with different features show heterogeneous responses across the globe. Eco‐physiological constraints likely increase the importance of spatial heterogeneity of climate, while dispersal limitations magnify the relevance of physical barriers (mountain chains and long‐term tectonic instability). Integrating among‐taxa heterogeneity into analyses thus provides a more complete view of how different processes determine biodiversity variation across the globe. [ABSTRACT FROM AUTHOR]

Aim: The diversity of brood size across animal species exceeds the diversity of most other life‐history traits. In some environments, reproductive success increases with brood size, whereas in others it increases with smaller broods. The dominant hypothesis explaining such diversity predicts that selection on brood size varies along climatic gradients, creating latitudinal fecundity patterns. Another hypothesis predicts that diversity in fecundity arises among species adapted to different microhabitats within assemblages. A more recent hypothesis concerned with the consequences of these evolutionary processes in the era of anthropogenic environmental change predicts that low‐fecundity species might fail to recover from demographic collapses caused by rapid environmental alterations, making them more susceptible to extinctions. These hypotheses have been addressed predominantly in endotherms and only rarely in other taxa. Here, we address all three hypotheses in amphibians globally. Location: Global. Time period: Present. Major taxa studied: Class Amphibia. Methods: Using a dataset spanning 2,045 species from all three amphibian orders, we adopt multiple phylogenetic approaches to investigate the association between brood size and climatic, ecological and phenotypic predictors, and according to species conservation status. Results: Brood size increases with latitude. This tendency is much stronger in frogs, where temperature seasonality is the dominant driver, whereas salamander fecundity increases towards regions with more constant rainfall. These relationships vary across continents but confirm seasonality as the key driver of fecundity. Ecologically, nesting sites predict brood size in frogs, but not in salamanders. Finally, we show that extinction risk increases consistently with decreasing fecundity across amphibians, whereas body size is a "by‐product" correlate of extinction, given its relationship with fecundity. Main conclusions: Climatic seasonality and microhabitats are primary drivers of fecundity evolution. Our finding that low fecundity increases extinction risk reinforces the need to refocus extinction hypotheses based on a suggested role for body size. [ABSTRACT FROM AUTHOR]

Motivation: A species' diet is central to understanding many aspects of its biology, including its behaviour, movement, and ecological niche. The diets of terrestrial carnivorous mammals, defined here as species primarily consuming other mammals (hereafter, mammal‐consumers), have been extensively studied and can vary in the proportion of different food types, and species, consumed across their geographic ranges. Accessibility to data capturing such variation in diets of mammal‐consumers across the variety of ecosystems they occur in would provide valuable information for conservation, and open research avenues for macroevolution and macroecology. However, data on mammal‐consumer diets across their geographic ranges have not been systematically collated. Here, we present CarniDIET (version 1.0), an open‐access database containing quantitative data on the diets of terrestrial mammal‐consumers collated from the literature. Main types of variable contained: Diet records capturing the percentage of mammalian prey, to the highest taxonomic resolution available, and non‐mammalian food types (e.g., birds, invertebrates) in the diets of mammal‐consumers at specific sites and times. Associated data with each diet record include, where available, age and sex of mammal‐consumer, sample size, sample origin, and quantification method as well as spatial and temporal variables including dates, season, study site, altitude and coordinates. Spatial location and grain: Global, terrestrial. The spatial grain varies among sites from 0.03 to 100,000 km2, with a median of 170 km2. Study centroids are provided as latitude‐longitude coordinates. Time period and grain: Original diet samples were collected between 1933 and 2017, with half of studies collected between 1994 and 2008. Studies summarize diets from 1 month to 66 years, with a median of 1 year. Major taxa and level of measurement: Terrestrial carnivorous mammals that primarily consume other mammals (103 species). Studies generally represent species' population averages, although can include demographic breakdowns. [ABSTRACT FROM AUTHOR]

Radiations of ectothermic vertebrates across cold climates depend on the coordinated evolution of multiple traits that compensate for the constraints imposed by limited and fluctuating resources, such as temperature, food and oxygen. One of nature's most prolific such radiations, Liolaemus lizards, has diversified across the extreme cold climates of the Andes and Patagonia. Remarkably, the prevailing patterns of reptile herbivory are opposed by Liolaemus which, in contrast with lizards generally, have repeatedly evolved plant consumption across small-bodied species from cold climates. Herbivory is hypothesized to depend on the evolution of multiple traits that maximize absorption of nutrients from an intrinsically poor-quality diet, such as increases in gastrointestinal tract size and increases in the density of nematodes in the intestine that may assist with plant digestion. Here, a comparative phylogenetic approach across Liolaemus species is implemented to test these hypotheses, which have only been investigated nonphylogenetically. Results reveal that intestine length increases consistently with increasing herbivory, whereas stomach size or nematode load are not associated with plant consumption. Body size plays no role in herbivory either. Consequently, this evidence places emphasis on the enlargement of the intestine to facilitate the evolution of herbivory in cold climates. [ABSTRACT FROM AUTHOR]

Abstract Background The impact of environmental gradients on the evolution of life history traits is a central issue in macroecology and evolutionary biology. A number of hypotheses have been formulated to explain factors shaping patterns of variation in animal mass. One such example is Bergmann's rule, which predicts that body size will be positively correlated with latitude and elevation, and hence, with decreasing environmental temperatures. A generally accepted explanation for this phenotypic response is that as body mass increases, body surface area gets proportionally smaller, which contributes to reduced rates of heat-loss. Phylogenetic and non-phylogenetic evidence reveals that endotherms follow Bergmann's rule. In contrast, while previous non-phylogenetic studies supported this prediction in up to 75% of ectotherms, recent phylogenetic comparative analyses suggest that its validity for these organisms is controversial and less understood. Moreover, little attention has been paid to why some ectotherms conform to this rule, while others do not. Here, we investigate Bergmann's rule in the six main clades forming the Liolaemus genus, one of the largest and most environmentally diverse genera of terrestrial vertebrates. A recent study conducted on some species belonging to four of these six clades concluded that Liolaemus species follow Bergmann's rule, representing the only known phylogenetic support for this model in lizards. However, a later reassessment of this evidence, performed on one of the four analysed clades, produced contrasting conclusions. Results Our results fail to support Bergmann's rule in Liolaemus lizards. Non-phylogenetic and phylogenetic analyses showed that none of the studied clades experience increasing body size with increasing latitude and elevation. Conclusion Most physiological and behavioural processes in ectotherms depend directly upon their body temperature. In cold environments, adaptations to gain heat rapidly are under strong positive selection to allow optimal feeding, mating and predator avoidance. Therefore, evolution of larger body size in colder environments appears to be a disadvantageous thermoregulatory strategy. The repeated lack of support for Bergmann's rule in ectotherms suggests that this model should be recognized as a valid rule exclusively for endotherms.

Aim: Body size explains most of the variation in fitness within animal populations and is therefore under constant selection from ecological and reproductive pressures, which often promote its evolution in sex‐specific directions, leading to sexual size dimorphism (SSD). Several hypotheses have been proposed to explain the vast diversity of SSD across species. These hypotheses emphasize: (a) the mate competition benefits to larger male size (sexual selection); (b) the benefits of larger female size for fecundity (fecundity selection); (c) the simultaneous benefits of niche divergence for males and females to reduce intersexual competition for ecological resources (natural selection); and (d) the underlying impact of geographical variation in climatic pressures expected to shape large‐scale patterns of SSD in synergy with the above selection pressures (e.g., intensification of fecundity selection as breeding seasons shorten). Based on a new, global‐scale amphibian dataset, we address the shortage of large‐scale, integrative tests of these four hypotheses. Location: Global. Time period: Extant. Major taxa studied: Class Amphibia. Methods: Using a > 3,500 species dataset spanning body size, ecological, life‐history, geographical and climatic data, we performed phylogenetic linear models to address the sexual, fecundity, ecological and climatic hypotheses of SSD. Results: Evolution of SSD is discordant between anurans and salamanders. Anuran SSD is shaped by climate (male‐biased SSD increases with temperature seasonality) and by nesting site. In salamanders, SSD converges across species that occupy the same types of microhabitats ("ecodimorphs"), whereas reproductive or climatic pressures have no effects on their SSD. These contrasts are associated with latitudinal gradients of SSD in anurans, but not in salamanders. Main conclusions: Amphibian SSD is driven by ecological and climatic pressures, whereas no roles for sexual or fecundity selection were detected. We show that macroevolutionary processes determined by different forms of selection lead to latitudinal patterns of trait diversity, and the lack of them. [ABSTRACT FROM AUTHOR]

Aim: Body size frequency distributions are often skewed to the right, with a greater frequency of small‐sized species. Right skewness can appear when speciation is biased towards small species and extinction towards large ones. In contrast, limits imposed by environmental constraints will select taxa to co‐occur in assemblages and can modify size distributions to the left or to the right. We analysed whether the shape of size distributions of anurans is related to diversification rates and how the environment might also be creating the observed patterns. Location: The Western Hemisphere. Time period: Current. Major taxa studied: Anurans. Methods: We computed diversification rates from a dated phylogeny and obtained data for body size, spatial distribution and the climate (annual temperature, potential evapotranspiration and normalized difference vegetation index) inhabited by 2,598 anuran species to analyse the relationship between diversification rates and body size. We then used an assemblage‐based approach to test whether the climate is acting together with species evolutionary history to generate skewed distributions of body sizes at local sites. Results: Skewness was positively correlated with size‐biased speciation and extinction, whereas it was negatively correlated with net diversification. After the inclusion of environmental predictors, the explanatory power of our models increased significantly. When ranking the predictors, evolutionary rates remained first, followed by a secondary role of environmental variables. Main conclusions: Despite the high frequency of right‐skewed body size distributions, anuran assemblages of the New World showed a variation of skewness that can be explained by faster net diversification (speciation minus extinction) at modal sizes. We conclude that size‐biased evolutionary rates and the environment both have a role in defining the proportion of small and large sizes at local scales. [ABSTRACT FROM AUTHOR]