Racer Goby Phylogeography
The racer goby Babka gymnotrachelus, along with several other neogobiin fishes, has been spreading north and west from its native Ponto-Caspian range for the past two decades via shipping and canals. It has been predicted as a likely future invader of the North American Great Lakes, where it would join its neogobiin relatives - the round and freshwater tubenose gobies. The present study is the first to analyze the population genetic and biogeographic relationships of the racer goby, establishing a baseline to aid interpretation of its future spread patterns and likely donor-recipient population relationships. The mitochondrial DNA cytochrome b gene was sequenced from representative areas of the racer goby’s range, including rivers of the northern Black Sea and areas of spread upstream in the Danube River and outside the Ponto-Caspian region to the Vistula River in Poland. Results discerned nine haplotypes, with few shared among drainages of native rivers and most sites housing unique alleles. Racer goby populations significantly diverged among watersheds, supporting historic low migration and little non-anthropogenic gene flow. The Dnieper River was identified as a likely donor source for the Vistula River colonization, where appreciable variability suggests a relatively large number of founding genotypes.
Figure 1. Map indicating locations of sampling sites (numbered 1-8) surrounding the Black and Azov Seas in Europe. Solid shading indicates original range of the racer goby Babka gymnotrachelus and hatching denotes regions of range expansion, following Miller (2003). Letters designate haplotypes (A-I) found at each location. (Note that some of our collections are located outside the published range expansion areas, attributed to more recent spread).
Figure 2. Haplotype network (modeled after Avise, 2000) for mitochondrial cytochrome b DNA sequences of the racer goby Babka gymnotrachelus. Each circle represents a unique haplotype denoted by A-G (see Table I). Solid dashes on lines connecting the haplotypes represent the number of nucleotide substitutions that differentiate them. Unfilled curved dashes indicate a reversal (homoplasy) to a previous base.
Ohayon, J.L. & C. A. Stepien. 2007. Genetic and biogeographic relationships of the racer goby Neogobius gymnotrachelus (Gobiidae: Teleostei) from introduced and native Eurasian locations. Journal of Fish Biology 71 (Supplement C), 360-370.
Jennie Ohayon, NSF REU 2006