Orogeny and climate change jointly shaped elevational speciation and introgression within Pachygrontha antennata and...

The formation and evolution of biogeographic processes are shaped by the long-term interplay of multiple biotic and abiotic factors. Compared with the Qinghai-Tibetan Plateauand Himalayas, the Hengduan Mountains region experienced rapid and relatively recent orogenic activity, primarily between the late Miocene to late Pliocene, a period marked by significant climatic change. This makes the Hengduan Mountains an ideal system for investigating how orogeny, climate change, and biological processes collectively influence species divergence and distribution patterns. Using ddRAD-seq data, we reconstructed the divergence history of Pachygrontha antennata and its closely related species. Our results indicate that the speciation of four clearly delineated lineages occurred near the Miocene-Pliocene boundary along the eastern margin of the Qinghai-Tibet Plateau, coinciding with major tectonic events and paleoclimatic oscillations. Orogeny generated diverse ecological niches along elevational gradients, while pronounced climatic shifts facilitated their expansion and colonization. Notably, during interglacial dispersal, populations at the leading edge ofthe low-elevation speciesP. antennatacame into secondary contact with high-elevationP. sp.along the western margin of the Sichuan Basin. Thisinteraction resulted in bidirectional but asymmetric gene flow, allowing P. antennata to retain ancestral genetic components shared with P. sp.and develop analogous genetic characteristics, which may have enhanced the high-elevation adaptability of the P. antennata population. Overall, our research reveals how abiotic factors-including orogeny and climate change-interact with biotic processes such as adaptive evolution and genetic introgression to shape species divergence and distribution dynamics.