J Syst Evol ›› 2021, Vol. 59 ›› Issue (1): 44-57.DOI: 10.1111/jse.12593

• Research Articles • Previous Articles     Next Articles

Restriction‐site associated DNA sequencing data reveal a radiation of willow species (Salix L., Salicaceae) in the Hengduan Mountains and adjacent areas

Li He1,2,3* , Natascha Dorothea Wagner2, and Elvira Hörandl2   

  1. 1College of Forestry, Fujian Agriculture and Forestry University, Fuzhou 350002, China
    2Department of Systematics, Biodiversity and Evolution of Plants (with Herbarium), University of Goettingen, Göttingen, Germany
    3College of Biological Sciences and Technology, Beijing Forestry University, Beijing 100083, China
  • Received:2019-05-10 Accepted:2020-04-19 Online:2020-04-24 Published:2021-01-01

Abstract: The Hengduan Mountains (HDM) in China are an important hotspot of plant diversity and endemism, and are considered to be a secondary diversification center for the woody plant genus Salix L. (Salicaceae). Here we aimed to reconstruct the spatiotemporal evolution of the Salix ChamaetiaVetrix clade in the HDM and to test for the occurrence of a local radiation. We inferred phylogenetic relationships based on more than 34 000 restriction‐site associated DNA loci from 27 species. Phylogenetic analyses recovered a well‐resolved tree topology with two major clades, the Eurasian clade and the HDM clade, with a divergence time of ca. 23.9 Ma. Species in the HDM clade originated in the northern part of the range and adjacent areas, and then dispersed into the southern HDM, westwards to the Himalayas and eastwards to the Qinling Mountains. Niche modelling analyses reveal that range contractions occurred in the northern areas during the last glacial maximum, while southward expansions resulted in range overlaps. Reconstructions of character evolution related to plant height, inflorescence, and flower morphology suggest that adaptations to altitudinal distribution contributed to the diversification of the HDM willows. Our data support the occurrence of a radiation in the HDM within the Salix ChamaetiaVetrix clade. Dispersal within the mountain system, and to adjacent regions, in addition to survival in glacial refugia shaped the biogeographical history of the clade, while adaptations of the HDM willows along an altitudinal gradient could be important ecological factors explaining the high species diversity of Salix in this area.

Key words: Chamaetia‐Vetrix clade, divergence time, morphological adaptation, mountain radiation, phylogenomics, Qinghai–Tibetan Plateau