Divergent Lineages in the de Winton's Shrew Complex (Eulipotyphla: Soricidae) From China: Assessing Evidence for Incipient Speciation

ABSTRACT Speciation is a fundamental evolutionary process, with incipient species crucial for understanding its mechanisms and the origins of species. Here, we analysed the genetic structure of the de Winton's shrew (Eulipotyphla: Soricidae) species complex using 140 samples to investigate its speciation patterns. This species complex belongs to the genus Chodsigoa , a group of shrews widely distributed in China and characterised by the absence of the fourth upper unicuspid tooth. We performed principal component analysis and discriminant analysis on cranial measurement data to examine morphological divergence. The molecular results suggested that the divergence time of this species complex began 2.82 to 7.08 million years ago, resulting in the formation of three divergent lineages with minimal morphological differences. Specifically, during the Pleistocene, climatic upheavals forced these lineages into refugia within the Hengduan Mountains, where the region's complex topography promoted isolation and facilitated both genetic and morphological divergence. During the more stable climate of the Last Glacial Maximum, range expansion and gene flow among populations occurred, thereby shaping the three divergent lineages. Our results also revealed that the Hengduan Mountains, a recognised biodiversity hotspot, harbour significant hidden diversity, shaped by complex evolutionary processes, geological history and climatic fluctuations. In addition, C. h. hypsibia and C. h. larvarum show no significant genetic or morphological differences, suggesting that the subspecies status of C. h. larvarum should be invalid.