Invasion Genetics of the Eurasian Round Goby: Spatial and Temporal Patterns Across North America

The genetic composition of an exotic introduction is believed to be important for its establishment and spread. We evaluate the genetic composition and development of population genetic structure across the North American invasion of the Eurasian round goby Neogobius melanostomus, dating from its 1990 appearance in the Great Lakes via ballast water to the present. We test the central hypothesis of whether the round goby's population genetic composition has changed spatially and temporally across the invasion's history. We analyze mtDNA cytochrome b gene sequences and 8 nuclear microsatellite loci for 1300+ round gobies from 25 North American and 22 Eurasian locations, representing its invasive and native ranges.  We also test temporal patterns from 2-3 time periods at 5 locations, using AMOVA, F_ST analogs, neighbor-joining trees, haplotype networks, Bayesian assignment tests, Mantel tests, and Monmonier barrier analysis. Results show: (1) the southern Dnieper River Black Sea port at Kherson, Ukraine was the primary donor source to the North American invasion, supplemented by other secondary sources, (2) the invasion exhibits high genetic diversity and no founder effect, (3) significant spatial genetic structuring characterizes its exotic and native ranges, (4) some newer fringe spread areas fit a “leading edge” model with less genetic variability, whereas others have high diversity, and (5) peripheral invasion sites changed significantly over time, towards net gain of alleles, whereas original colonization sites remain genetically consistent. We conclude that high genetic diversity likely enhances the round goby’s ecological success. Spatial genetic structure across the exotic range reflects the history of multiple invasion foundings and local genetic predominance of established colonists.