Polyploid and hybrid evolution in roses east of the Rocky Mountains

Abstract

This study investigates the impact of hybridization and polyploidy in the evolution of eastern North American roses. We explore these processes in theRosa carolinacomplex (sectionCinnamomeae), which consists of five diploid and three tetraploid species. To clarify the status and origins of polyploids, a haplotype network (statistical parsimony) of the glyceraldehyde 3‐phosphate dehydrogenase (GAPDH) nuclear gene was estimated for polyploids of the complex and for diploids of sectionCinnamomeaein North America. A genealogical approach helped to decipher the evolutionary history of polyploids from noise created by hybridization, incomplete lineage sorting, and allelic segregation. At the diploid level, species west of the Rocky Mountains are distinct from eastern species. In the east, two groups of diploids were found: one consists ofR. blandaandR. woodsiiand the other ofR. foliolosa,R. nitida, andR. palustris. Only eastern diploids are involved in the origins of the polyploids.Rosa arkansanais derived from theblanda–woodsiigroup,R. virginianaoriginated from thefoliolosa–nitida–palustrisgroup, andR. carolinais derived from a hybrid between the two diploid groups. The distinct origins of these polyploid taxa support the hypothesis that the three polyploids are separate species.