mtDNA singletons as evidence of a post-invasion genetic bottleneck in yellowfin goby Acanthogobius flavimanus from San Francisco Bay, California

Yellowfin goby, a fish native to East Asia, was first reported in northern California (San Francisco Bay) in 1963 and in southern California (Los Angeles Harbor) in 1979. Over the past 4 decades, it has spread to other northern and southern California estuaries, respectively. The documented expansion of yellowfin goby in California provided an opportunity to study potential founder effects in a marine invasive fish by seeking evidence of reductions in mtDNA singleton haplotypes consistent with an expected loss of overall genetic diversity. We obtained samples of yellowfin goby from San Francisco Bay in northern California, from 2 small estuaries in southern California, and from Tokyo Bay, Japan, the presumed source population. The mtDNA control region was fully sequenced and analyzed for a total of 216 specimens, where the numbers of singleton haplotypes relative to the total number of haplotypes in each sample were compared to predictions from a regression analysis of singletons on total haplotypes. AMOVA comparisons among haplotype frequencies were also performed. Singleton haplotypes were significantly fewer than predicted among yellowfin goby of San Francisco Bay, indicating some loss of genetic diversity in that invasive population. Singletons were not significantly fewer than prediction among yellowfin goby of Tokyo Bay or of southern California. phi sub(ST) values were not significantly different between San Francisco and Tokyo bays, but were different between San Francisco Bay in northern California and southern California locations, suggesting separate introductions to California.