Idiosyncrasies Unveiled: Examining the Pace, Patterns and Predictors of Biotic Diversification in Peninsular India

The Peninsular Indian Plate, one of the oldest regions of diversification in tropical Asia, harbours highly diverse and endemic biota. However, our understanding of the diversification dynamics of its biota within a quantitative framework remains limited. To address this, we used time-calibrated molecular phylogenies and birth-death models to examine the tempo, mode and drivers of diversification across 33 well-studied endemic clades (~770 species). Among peninsular Indian clades, angiosperms diversified the fastest, whereas invertebrates diversified the slowest. Younger clades of Asian origin diversified more rapidly than the older, relictual Gondwanan clades. Evolutionary relatedness explained the disparities in diversification rates across taxonomic groups and biogeographic origins. A gradual accumulation of diversity was supported in 17 clades, suggesting that the historical stability of their habitat was an important driver. Miocene intensification of monsoons, and aridification and fluctuations in paleotemperature explained diversification patterns in the remaining 16 clades. Our results highlight the role of regional biogeography, geoclimatic processes and phylogenetic history in governing diversification dynamics in the tropics.