Oral Paper

         Phylogenomics

resolving the complex evolutionary history of North American shrub willows (Salix L.)

Presenting Author
Natascha Wagner
Description
Willows are distributed in the Northern Hemisphere and comprise about 450 species. In North America about 140 Salix species occur, more than 100 belong to the so-called “shrub willows” (Chamaetia/Vetrix clade). The huge diversity of Salix subgenus Vetrix in North America and the lack of phylogenetic resolution within this clade was a challenging, however fascinating mystery for decades. The taxonomy is still under debate and complicated by measures of ancient and recent hybridization as well as polyploidization. In this study, about 50 species representing 19 described sections (sensu Argus 1999) from the USA and Canada were included and combined with about 100 species from Europe and Asia. With a RAD sequencing approach it was possible to produce a well-resolved phylogeny of 145 shrub willow species (235 accessions) based on ten thousands of RAD loci. The resulting tree showed an exclusively “North American clade” containing the majority of included species from this region in sister position to a “Eurasian clade”. The latter included samples of worldwide distributed species as well as some North American endemics. Most species were monophyletic, however, several North American species were polyphyletic. The results revealed that the diversity of subgenus Vetrix in North America was shaped by a radiation as well as several migration and long distance dispersal events.