Genetic Portraits Of Introduced Gobies And Mussels PDF Download

The growing numbers of species introductions, with many having significant ecological and economic impacts, constitute one of the greatest challenges facing our native ecosystems today. To make correct ecological comparisons among native and introduced populations and minimize their further spread, we must (1) identify the introduced species/taxon/population correctly and (2) determine its source population(s) and its transmission pathways. This dissertation study analyzes and compares the population genetic and phylogeographic structure of three successful invasions by Ponto-Caspian species into the North American Great Lakes and beyond: the round goby Neogobius melanostomus and the dreissenid mussels Dreissena polymorpha and Dreissena rostriformis bugensis. In Chapters 2 and 3 we describe evidence for two subspecies of round goby, both of which have expanded their range. From this background information, likely sources are identified for invasive populations in Eurasia and North America. In Chapter 4, the genetic structure of zebra and quagga mussels in North America is analyzed in comparison with sites in Eurasia. Zebra mussel populations have appreciable genetic diversity, whereas quagga mussel populations from the Colorado River and California show some founder effects. The population genetic composition of both species changed over time at given sites; with some adding alleles from adjacent populations, some losing them, and all retaining closest similarity to their original composition. Zebra and quagga mussels from the western United States assign to possible origins from the St. Lawrence River and Lake Ontario, respectively. These assignments suggest that overland colonization pathways via recreational boats do not necessarily reflect the most proximate connections. The results show that all three species likely experienced multiple introductions into the Great Lakes, which brought a large proportion of the native genetic diversity to North America. This created significant genetic structure within their respective introduced ranges. The round goby and the quagga mussel were introduced from their native range, in contrast to the zebra mussel which whose origins North American origins trace to secondary spread from previously invaded regions in Northern and Central Europe. This dissertation demonstrates the utility of molecular techniques to invasive species management, by identifying the pathways connecting source populations to new colonies.