Influence of Demographic and Genetic Factors on Genetic Variation in Introduced Populations of Oregon Chub

Population introductions played an important role in the recovery of Oregon chub (Oregonichthys crameri), a small floodplain minnow found in western Oregon. Unlike many introduction efforts, introduced populations of Oregon chub were founded using large numbers of individuals and each population had a unique introduction history (i.e., number of founders, source population(s) selected, duration of the introduction effort, etc.). We examined 13 introduced populations and their respective sources to evaluate the relationship between introduction history and genetic diversity. Genetic variation was significantly lower in one introduced population, and three introduced populations showed evidence of a genetic bottleneck due to heterozygote excess. Populations introduced using multiple sources had greater diversity than populations with a single source. When multiple source populations were used, all source populations contributed to the introduced population. Using correlation analyses and general linear models, we explored the relationship between introduction history and genetic diversity. Genetic diversity in the source population had the greatest influence on genetic diversity in the introduced population, but the number of founders and the number of source populations were also important. Overall, the Oregon chub introduction program was highly successful at capturing the genetic variation observed in natural populations.