Format: ORAL

Pia Marincek1, tinne Lveill-Bourret 2, Stphane M. Bailleul3, Martin Volf4, Li He5, Loc Pittet1, Elvira Hrandl1, Tommi Nyman6, Sophie Karrenberg7, Campbell O. Webb8, Maria Tomoschevich9 Natascha D. Wagner1

1 Department of Systematics, Biodiversity and Evolution of Plants (with Herbarium), University of Goettingen, Untere Karspüle 2, D-37073 Göttingen, Germany 2 Institut de recherche en biologie végétale (IRBV), Département de sciences biologiques, Université de Montréal, Montréal, QC, H1X 2B2, Canada 3 Division Recherche et développement scientifique, Jardin botanique de Montréal, 4101 Sherbrooke est, Montréal, QC, H1X 2B2, Canada 4 Biology Centre of the Czech Academy of Sciences, Branisovska 31, 37005 Ceske Budejovice, Czech Republic 5 Eastern China Conservation Centre for Wild Endangered Plant Resources, Shanghai Chenshan Botanical Garden, 201602 Shanghai, China 6 Department of Ecosystems in the Barents Region, NIBIO Svanhovd Research Station, Svanhovd 20, NO-9925 Svanvik, Norway 7 Department of Ecology and Genetics, Plant Ecology and Evolution, University of Uppsala, SE- Norbyvägen 18 D, 752 36 UPPSALA, Sweden 8 Museum of the North, University of Alaska, Fairbanks, AK 99711, USA 9 Central Siberian Botanical Garden of the Siberian Branch of the Russian Academy of Science, Herbarium, Zolotodolinskya Street 101, RU-630090 Novosibirsk, Russia

Genus Salix is the largest genus of family Salicaceae with about 450 species of woody plants predominantly inhabiting the Northern Hemisphere. A large portion of the genus, about 300 species organized in 40 sections, is represented by the so called shrub willows belonging to subgenera Chamaetia and Vetrix that form a monophyletic clade. Several traditional molecular markers could not resolve the relationships within this clade. Traditional, morphology-based taxonomical classification continues to be under question due to vast inter- and intra-specific phenotypic variation and a lack of informative characters. The processes of hybridization, introgression and polyploidization played an important role in the evolution of willows and further complicated research of this genus. Thus, shrub willows remain a hard challenge that fascinates biologists to this day. In our project, we selected a RAD sequencing approach to generate a huge number of SNPs to disentangle the interrelations of shrub willows. This way we wanted to find evidence to justify or refute the current sectional classification. We were able to sequence more than 400 individuals of over 120 species of shrub willows collected worldwide. Using a maximum likelihood estimation, we built a well resolved phylogeny. Our data revealed that most of the species form monophyletic clades, though some exceptions show polyphyly. Morphological traits have evolved multiple times in shrub willows and current sectional classification does not reflect true biological relationships. Polyploidy evolved numerous times as a result of allo- and auto-polyploidization events. Patterns of species radiation could be observed in regions such as North America and Chinese Hengduan mountains. Migration and long distance dispersal further shaped the diversity of shrub willows. Our research presents a strong backbone for future studies on shrub willows regarding taxonomy, hybridization, polyploidization, ecology and many more.