Pleistocene Forest Stability Predicts Patterns of Frog Diversity in Central Africa.

Understanding why diversity is unevenly distributed across the globe is central to ecology and evolution. Focusing on Afrobatrachian frogs of the Lower Guinean Forests of western Central Africa, we combined Pleistocene-to-present palaeoclimatic reconstructions with ecological niche models to delineate areas of long-term habitat stability ("refugia"). We tested whether refugia or contemporary climate best explain present-day patterns of species richness, phylogenetic diversity, and weighted endemism. Strict and relaxed stability thresholds identified core refugia that occupy only a small fraction of the landscape yet harbor the highest values for each diversity metric. Spatial regression models revealed that past forest stability accounted for 65%-71% of the spatial variance in richness and phylogenetic diversity, far exceeding the explanatory power of current abiotic conditions, and that all diversity metrics declined sharply with increasing distance from the edge of stable forest. Because less than 15% of inferred refugia fall within existing protected areas, expanding conservation coverage to include the most stable forest blocks would increase mean amphibian richness in protected areas by nearly one-fifth. Our results demonstrate that the legacy of Pleistocene forest dynamics outweighs contemporary climate in shaping amphibian diversity within this tropical hotspot. We provide a transferable, quantitative workflow for integrating past habitat stability into regional conservation planning.