Data for: Classic hypotheses of area, time, and climatic stability fall short in explaining high tropical species richness

Tropical biodiversity overshadows the number of species inhabiting other
regions. Age, area, and stability constitute three classical ideas used to
explain the higher richness in these warm and humid zones. In this study,
we measured the global dynamics of tropical, arid, temperate, cold, and
polar climate zones over the last 5 million years (Ma). We aimed to
evaluate whether the age, area, and stability of these climate zones
contribute to explaining the observed differences in species richness. We
classified the paleoclimatic layers generated by the PALEO-PGEM climatic
emulator – temperature and precipitation for the last 5 Ma at 1,000-year
intervals – into the main Köppen-Geiger climate zones: tropical, arid,
temperate, cold, and polar. We then calculated three variables: age, area,
and stability. Age represents the duration that each map cell has remained
within its current climate zone since its last change (map cell-based
measure). Area quantifies the total extent of each climate zone over time
by summing all map cells corresponding to that climate zone (climate
zone-based measure). Stability indicates the number of times a given map
cell changed between climate zones over time (map cell-based measure). We
implemented regression and correlation tests, Structural Equation Models,
and decision trees to measure the relationship between these estimates and
current global patterns of amphibian, bird, and mammal
richness. Our results indicate that age, area, and stability do
not account for the observed differences in species richness among the 5
climate zones. None of these classical hypotheses alone can
explain the high vertebrate tropical richness observed. Further
investigation, incorporating additional taxa (e.g., invertebrates or
plants), or integrating new perspectives (such as the influence of local
variations in diversification processes) will provide a more comprehensive
understanding of the factors shaping large-scale biodiversity patterns.