Origin and evolution of Fragaria cascadensis

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Polyploid hybrid speciation is one of the major driver of plant speciation. The ancestor of all angiosperms was probably polyploid, as were the ancestors of several important crop plants (e.g., wheat (Triticum L.) and strawberry (Fragaria L.)). To understand the evolution of polyploid hybrid species it is necessary to know which parental species contributed to the genome. This can be difficult, especially when several hybridization events occurred. Fragaria (Rosaceae) is a genus of 23 species containing the important crop species F. ×ananassa Duschesne ex Rozier. In Fragaria 11 of 23 species are polyploid hybrid species. There are tetra-, hexa-, octo- and decaploid species of which many are long known. In 2012 a new decaploid species, Fragaria cascadensis Hummer, was described. The ancestors of this species remain unclear, but it is suggested that it is a hybrid of F. vesca L. subsp. bracteata (A. Heller) Staudt and F. virginiana Mill. subsp. platypetala (Rydb.) Staudt. Due to its present distribution in the Cascade Range in Oregon (USA) a possible time frame for its evolution is after the melting of the Pleistocene glaciers in Oregon ca. 10,000 years ago. In this project I want to investigate the origin and evolution of this decaploid species. I will use target enrichment Hyb-Seq to obtain more than 10,000 loci of the nuclear genome and the plastome that can be compared with datasets of the potential parental species and aligned to the Fragaria vesca reference genome. With appropriate approximate Bayesian computation methods different models of origin (single vs. multiple origin) can be tested and divergence times will be calculated. The aim is to understand when, where and how often Fragaria cascadensis originated and how it evolved since then.