Insights into the drivers of radiating diversification in biodiversity hotspots using Saussurea (Asteraceae) as a case

The Qinghai-Tibet Plateau (QTP) encompasses areas with a remarkably high degree of biodiversity, harboring exceptional species-rich radiations. How these radiations formed by interacting with geology, climate and ecology remains seldom examined.We investigate the roles of abiotic (environmental) and biotic (species-intrinsic) factors in driving radiating diversification of Saussurea (Asteraceae) by deploying a number of time-dependent, paleoenvironment-dependent and trait-dependent models, as well as ecological distribution data.We show that three main clades of Saussurea begin to diversify in the Miocene almost simultaneously, with increasing diversification rates toward the present and negative dependence to paleotemperature. Acceleration in diversification rates are correlated with adaptive traits, as well climate lability, niche breadth and species range.We conclude that fluctuation of paleoclimate along with complex QTP environments provided opportunities for increased diversification rates of Saussurea with diverse adaptive traits, highlighting the importance of combinations of clade-specific traits and ecological niches in driving rapid radiation.