EAPSI: Evolution and Biogeography of an East Asian-North American Distribution in Sedges, a Hyper-Diverse Group of Flowering Plants

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Sedges (genus: Carex) are one of the five largest genera of flowering plants, and the most diverse plant genus in the temperate zone. Sedges, with an estimated 2100 species, are an ideal group for examining questions about broader patterns of biodiversity and evolution due to 1) high species diversity in the genus, 2) speciation driven by microhabitat specialization, and 3) restricted ability for physical dispersal. Within this genus, a clade of about 60 species in sections Laxiflorae, Paniceae, Limosae, and Bicolores are distributed widely across North America and Eurasia, with two centers of biodiversity in the eastern United States and Japan. The project will utilize a combination of molecular systematics and biogeographic methods to reconstruct the evolutionary relationships of these sedges and model their geographic range shifts through time. The award will allow the researcher to travel to Japan to sample East Asian sedges, including narrowly distributed Japanese endemics. Laboratory work will produce DNA sequences that integrate with data previously generated by the principal investigator for North American sedges. This is a collaborative research project with Dr. Takuji Hoshino, a plant systematist and sedge expert at the Okayama University of Science. During the research in Japan, DNA will be extracted from the collected silica-dried leaf samples. Six DNA sequence regions will be targeted and amplified by PCR. The generated DNA sequences will be edited with Sequencher, then aligned manually and with the program MUSCLE. BEAST, a Bayesian program for phylogenetic analyses, will be used to reconstruct a combined character phylogeny and perform divergence dating by calibrating node ages with fossil data. The research will test the hypothesis that the clade was once widespread throughout a continuous forest in the Northern Hemisphere, and that the present-day patterns of diversity are due to recent species radiations in both eastern North America and Japan. This work will investigate role that Beringia played in shaping patterns of diversity in the present-day flora, and examine long-term range shifts in dispersal-limited flora due to changes in climate and environment. This award under the East Asia and Pacific Summer Institutes program supports summer research by a U.S. graduate student and is jointly funded by NSF and the Japan Society for the Promotion of Science.