Diversity gradients of terrestrial vertebrates – substantial variations about a common theme

Abstract

Environmental factors, such as temperature, precipitation, and elevation, explain most of the variation in species richness at the global scale. Nevertheless, richness patterns may have different drivers across taxa and regions. To date, a comprehensive global examination of how various factors such as climate or topography drive patterns of species richness across all terrestrial vertebrates, using the same methods and predictors, has been lacking. Recent advances in species‐distribution data allowed us to model and examine the richness pattern of all terrestrial tetrapods comprehensively. We tested the relationship between environmental and biogeographical variables and richness of amphibians (5983 species), birds (9630), mammals (5004), reptiles (8939), and tetrapods as a whole, globally, and across biogeographical realms. We studied the effects of climatic, ecological, and biogeographic drivers using generalized additive models. Richness patterns and their environmental associations varied among taxa and realms. Overall precipitation was the predominant richness predictor. However, temperature was more important in realms where both cold and warm conditions exist. In the Indomalayan realm, elevational range was very important. Richness patterns of mammals, birds, and amphibians were strongly related to precipitation whereas reptile richness was mostly associated with temperature. Our results support the universal importance of precipitation but also suggest that future global‐scaled research should incorporate other relevant variables other than climate, such as elevational range, to gain a better understanding of the richness–environment relationship. By doing so, we can further advance our knowledge of the complex relationships between biodiversity and the environment.

A dataset containing speciation rates, uncertainty, and presence-absence matrices for more than 34,000 vertebrate species

“…At least for the DivRate based on the fair proportion approach and BAMM, the coefficient of variation for the 75% of the data remained below the 10% threshold, except for sharks. On the other hand, the presence-absence matrices successfully recovered the well-known latitudinal patterns of diversity for the five vertebrate groups (Jenkins et al, 2013; Raz et al, 2023), exhibiting a general trend of higher species richness in tropical regions (Fig. 3), although showing specific variations in the main areas with the highest species richnes.…”

Generation length of the world’s amphibians and reptiles

“…We used those primary climate variables to calculate 4 bioclimatic variables: mean annual temperature (bio01), temperature seasonality (bio04), as temperature influences reptiles and amphibians reproductive ecology and metabolism (Shine, 2005; Taylor et al, 2021), mean annual precipitation (bio12) and precipitation seasonality (bio15). Those variables explain most of the climatic variation at global scale (Buckley & Jetz, 2008; Raz et al, 2024) and other factors such as summer and winter temperatures exhibit significant correlations with linear combinations of these 4 variables. We retrieved species’ distribution from the IUCN Red List spatial data repository, which provided distribution information for 5,657 amphibians, 9,203 squamates and 121 testudines.…”

SquamBase—A database of squamate (Reptilia: Squamata) traits

“…With such great variation in basic biological attributes, it is unsurprising that squamates are ubiquitous in all terrestrial biomes, except the coldest ones, across all continents and tiny, often very remote, islands. Indeed, squamates are relatively more successful than other vertebrates in colonising and persisting in warm deserts and islands (Raz et al, 2024;Roll et al, 2017).…”