The interplay of abiotic and biotic factors likely drove one of the fastest plant radiations from tropical-subtropical Asia.

Abstract

Both biotic and abiotic factors are expected to drive species diversification, yet demonstrating their synergistic effects within a single framework is challenging and has rarely been studied. The recent and rapid radiation of the genus Aspidistra (cast-iron plant) provides an ideal system for examining these processes. Here, we generated restriction site-associated DNA sequencing data for 123 Aspidistra taxa and reconstructed well-resolved phylogenies using both concatenation- and coalescent-based approaches. Using a comprehensive suite of diversification models, we quantified the contributions of multiple biotic and abiotic factors and applied phylogenetic path analysis to detect their synergistic effects. Our phylogenetic analyses recovered two main clades that differ in stem habits. We found that the diversification of Aspidistra has been driven by both abiotic factors (paleotemperature and the East Asian monsoon) and biotic factors (interspecific competition and pollination mutualism). Notably, these drivers operated both independently and synergistically to facilitate the rapid radiation of Aspidistra. Beyond providing a robust phylogeny useful for classifying Aspidistra, we present a statistical framework for better understanding the macroevolutionary processes underlying rapid plant radiations. Our findings underscore the critical importance of integrating multiple biotic and abiotic drivers into a unified analytical framework to comprehensively understand diversification history.