LAUSR

Genetic compositions and comparative diversity of zebra (Dreissena polymorpha) and quagga (D. rostriformis) mussel populations are compared across their three decade-long histories as invasive species in the Hudson River and Lake Erie of North America. We analyze 15 nuclear DNA microsatellite loci for the zebra mussel and 10 for the quagga mussel. Results indicate that the Hudson River and Lake Erie zebra mussel populations slightly diverge in genetic compositions, and possess similar overall genetic diversity levels. The allelic composition of the Hudson River zebra mussel population significantly changed during the middle time period (2003) analyzed, suggesting genetic replacement. Yet, its overall levels of genetic diversity levels have stayed similar. In contrast, the Hudson River’s quagga mussel population has remained genetically consistent over time in both composition and diversity. Lake Erie’s zebra mussel population underwent slight change in allelic composition and increased in genetic diversity from the earliest timepoint, suggesting allelic supplementation from newly arriving propagules. In contrast, Lake Erie’s quagga mussel population has remained genetically consistent over time. The genetic composition of Lake Erie zebra mussel veliger larvae sampled in 2016 differed from its adult samples, attributable to gene flow from other areas and genetic admixture. Overall findings indicate that invasive populations may undergo significant genetic divergence or remain consistent over time, whose patterns may differ across their ranges and between related species. The population dynamics underlying their invasional successes thus may be complex.