PRJNA720697
Evolution of Castanea in North America: RADseq and ecological modeling reveal a history of radiation, range shifts, and disease.
Chestnuts and chinquapins are some of the best known and most widely loved of any plants in North America. Despite the fame of this clade, relatively little genomic sequencing has been done, and much is still unknown about their evolution. Here we use ddRAD data to infer the species-level phylogeny for Castanea and assess the phylogeography of the North American species using samples collected from populations that span the full extent of the species ranges. We also construct species distribution models using digitized herbarium specimens and observational data from field surveys. We identified strong population structure within Castanea dentata (American Chestnut) that reflects a stepwise northern migration since the Last Glacial Maximum. Our species distribution models further confirm this scenario and match closely with the fossil pollen record. We also found significant structure within the Castanea pumila lineage, most notably a genetic cluster that corresponds to the frequently recognized Castanea pumila var. ozarkensis. The two North American Castanea species have contrasting patterns of population structure, but each is typical of plant phylogeography in North America. Within the C. pumila complex we find novel genetic structure that provides new insights to C. pumila taxonomy. Our results also identify a series of distinctive populations that will be valuable in on going efforts to conserve and restore the Chestnuts and Chinquapins in North America.