Geographic isolation and climatic heterogeneity shape the genetic diversity of Blarinellini (Eulipotyphla: Soricidae) in the Hengduan Mountains

The Hengduan Mountains of southwestern China constitute a classic sky-island system shaped by complex topography and climatic history. We investigated the evolutionary history of the shrew tribe Blarinellini using 272 samples representing both genera and all four recognized species. Based on mitochondrial and nuclear sequence data, we reconstructed phylogenetic relationships, estimated divergence times, and examined population genetic structure and ecological niche dynamics. Our results support an early Miocene origin of Blarinellini (~18.2 million years). Population genetic analyses recovered five and four deeply divergent geographic lineages within Blarinella quadraticauda and B. wardi , respectively. Most genetic variation was partitioned among lineages, indicating strong long-term isolation. Lineage distributions closely correspond to major river systems and montane regions, suggesting that the effects of river barriers and sky-island fragmentation may have contributed to the observed patterns of diversification. Ecological niche models identified climatically stable habitats within the Hengduan Mountains across multiple glacial–interglacial cycles, whereas demographic analyses revealed recent expansion in a subset of lineages. Together, these results suggest that river barriers, sky-island fragmentation, and climatic change may have jointly contributed to diversification in Blarinellini, and suggest that evolutionary diversity within the tribe may be substantially underestimated. These findings highlight the dual role of the Hengduan Mountains as both a refuge preserving ancient lineages and a cradle generating new diversity.