Rapidin-situdiversification rates in Rhamnaceae explain the parallel evolution of high diversity in temperate biomes from global to local scales

Abstract

SummaryThe macroevolutionary processes that have shaped biodiversity across the temperate realm remain poorly understood and may have resulted from evolutionary dynamics related to diversification rates, dispersal rates, and colonization times, closely coupled with Cenozoic climate change.We integrated phylogenomic, environmental ordination, and macroevolutionary analyses for the cosmopolitan angiosperm family Rhamnaceae to disentangle the evolutionary processes that have contributed to high species diversity within and across temperate biomes.Our results show independent colonization of environmentally similar but geographically separated temperate regions mainly during the Oligocene, consistent with the global expansion of temperate biomes. High global, regional, and local temperate diversity was the result of highin-situdiversification rates, rather than high immigration rates or accumulation time, except for Southern China, which was colonized much earlier than other regions. The relatively common lineage dispersals out of temperate hotspots highlights strong source-sink dynamics across the cosmopolitan distribution of Rhamnaceae.The proliferation of temperate environments since the Oligocene may have provided the ecological opportunity for rapidin-situdiversification of Rhamnaceae across the temperate realm. Our study illustrates the importance of highin-situdiversification rates for the establishment of modern temperate biomes and biodiversity hotspots across spatial scales.

Dispersal modes affect Rhamnaceae diversification rates in a differentiated manner

“…Diversification rates were found to be higher for Rhamnaceae lineages with diplochory and myrmecochory compared to those taxa dispersed by wind, ballistics, or vertebrates (figure 2). Geological changes and climatic fluctuations have contributed to the rapid flourishing of angiosperms, as well as to the development of the modern flora on Earth since the late Cretaceous [88][89][90][91][92]. The evolution of the various dispersal modes may have provided opportunities for colonizing new and heterogeneous habitats and promoting diversification, such as in Rhamnaceae.…”