SG: Phylogenomic analyses of goldenrods (Solidago, Asteraceae) using herbarium specimens

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Goldenrods are a widespread, yet taxonomically challenging group of plants with an estimated 150 species that mainly live in North America. Previous attempts to determine how many species there are and how they are related have failed because of the large number of potential species involved, extensive hybridization among these species, and the seemingly recent evolutionary divergence of species within the group. The limited understanding of goldenrod biodiversity has slowed progress in plant evolutionary ecology. Goldenrods have emerged as a critical study system for many important processes including species formation, invasive species biology, nutrient cycling in soils, and pollination biology. This research will reconstruct evolutionary relationships in the group by using large amounts of DNA sequence data. Project participants, including three undergraduate researchers, will sample tissue from specimens representing all 150 putative goldenrod species under the guidance of a project collaborator who is the global expert on goldenrod taxonomy. This approach will allow the genealogy of this large genus to be reconstructed rapidly and economically, and will provide an essential evolutionary framework for other goldenrod researchers.This project will employ an anchored phylogenomics approach to capture DNA sequence data from 1200 locations across the genome of goldenrods (Solidago, Asteraceae). Multiple samples from each species will be obtained exclusively from herbarium specimens, which have been shown to harbor DNA of sufficient quantity and quality for this genomic technique. Sampling will focus on the 4200 Solidago herbarium specimens for which the research team and collaborators have previously obtained a chromosome count, with the cytotype of additional samples estimated using a highly-accurate microsatellite allele number approach. Both diploids-only and combined diploid/polyploid species trees will be reconstructed in order to establish both divergent and reticulate evolutionary events. Phylogenetic, taxonomic, and methodological results stemming from this research will be disseminated in scientific journals and more broadly through a Solidago-focused website maintained by a project collaborator.