The Effects of Floral and Ploidy Variation on Reproductive Isolation in Collinsia Parviflora and C.Grandiflora (Veronicaceae)

Understanding how new species are formed through the development of reproductive barriers is a major goal of evolutionary research. To determine how floral and genomic variation contribute to reproductive isolation between populations of Collinsia parviflora and C. grandiflora from British Columbia, Washington, Oregon and California, I surveyed flower size and genomic content in populations throughout that area. I found continuous variation in flower size and four distinct ploidy levels among the populations surveyed. Reciprocal crossing experiments between populations representing three flower size classes (small, intermediate and large) and four ploidy levels were performed. Total reproductive isolation was calculated based on fitness differences in seed production, F1 germination, F1 survival to flowering and F1 fertility and revealed that isolation among populations is due primarily to a combination of ploidy and flower size differences. The results of this study indicate that a reclassification of this group of Collinsia is in order.