Multiple introductions of the eastern fox squirrel (Sciurus niger) in California.

Eastern fox squirrels (Sciurus niger) have been introduced into California within the past 130 years. Recently, their range has been expanding at an alarming rate. Genetic diversity was assessed in 101 control region sequences of eastern fox squirrels from three geographic regions within California (Los Angeles County, Alameda and Contra Costa counties and Sacramento County) to determine if a single or multiple introductions occurred within California, as indicated by the detection of multiple haplotypes. A total of 11 haplotypes were discovered, with haplotypes rarely shared among geographic regions and no clustering by region in a haplotype network. This suggests that the introduction to different regions within California came from different source populations within the native range of the species. Haplotype diversity was highest in Los Angeles County. Due to a lack of phylogeographic structure in fox squirrels in their native range, it is difficult to identify the sources of all introductions.