Genome-wide analysis of Cushion willow provides insights into alpine plant divergence in a biodiversity hotspot

Funding: Strategic Priority Research Program of Chinese Academy of Sciences (XDA 20050203 (H.S.); Major Program of the NSFC 31590823 (H.S.); National Key R & D Program of China 2017YF0505200 (H.S.); NSFC (31670198 to J.C., 31560062 to Y.H.,31871271 to W.Z.); Science and Technology Research Program of KIB (NO.KIB2016005 to J.C.); Youth Innovation Promotion Association, CAS (J.C.), and Peking-Tsinghua Center for Life Science, the State Key Laboratory of Protein and PlantGene Research and Qidong-SLS Innovation Fund (W.Z.).The Hengduan Mountains (HDM) biodiversity hotspot exhibits exceptional alpine plant diversity. Here, we investigate factors driving intraspecific divergence within a HDM alpine species Salix brachista (Cushion willow), a common component of subnival assemblages. We produce a high-quality genome assembly for this species and characterize its genetic diversity, population structure and pattern of evolution by resequencing individuals collected across its distribution. We detect population divergence that has been shaped by a landscape of isolated sky island-like habitats displaying strong environmental heterogeneity across elevational gradients, combined with population size fluctuations that have occurred since approximately the late Miocene. These factors are likely important drivers of intraspecific divergence within Cushion willow and possibly other alpine plants with a similar distribution. Since intraspecific divergence is often the first step toward speciation, the same factors can be important contributors to the high alpine species diversity in the HDM.Publisher PDFPeer reviewe

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