Population genetics of northern pike (Esox lucius) introduced into Lake Davis, California

We used molecular genetic techniques to identify the source population of northern pike (Esox lucius) illegally introduced into Lake Davis, California, and to study the dynamics of genetic change since the introduction. We typed 10 tetranucleotide microsatellite loci from 11 populations and used measures of population differentiation, phylogenetic analysis, and assignment tests to determine the origins of the pre- and post-rotenone-treatment populations. We found that levels of genetic differentiation were low between the pre- and both post-treatment Lake Davis samples and phylogenetic analysis revealed that they were all closely related. Assignment tests classified a high proportion of posttreatment individuals to the original Lake Davis population. Consequently, our results indicate that the fish population that reappeared in 1999 and a subsequent sample in 2002 were descendents or survivors of the initial population. We were unable to assign the pre- or post-treatment individuals consistently to any one population from a panel of potential source populations, indicating that the ultimate source of the Lake Davis population was likely not sampled. Genetic signatures of a recent population bottleneck are evident in the samples from Lake Davis and the effective population size over the sampling period was approximately 7-12 individuals.