Gammarus lacustris possesses one of the largest ranges observed among freshwater Amphipoda, occurring from eastern Europe to southern China and Siberia, and into the western United States and Canada. A range this size is truly remarkable for a single amphipod species, given that they lack both a resting stage and a dispersal larval stage and thus, tend to be either restricted in range or local endemics. However, despite this curious range, G. lacustris seems to be a single species based on morphology. Previous research with Palearctic members of this species suggests that it is rather young, appearing during the Late Miocene or early Pliocene, reaching the far parts of its range like eastern Europe and North America during the Pleistocene. However, very little research into its Nearctic range has been conducted. Further research into its biogeographic history in this region will no doubt be of utility, as this species reached the North American continent relatively recently and was able to disperse rapidly, something none of the other Nearctic amphipod taxa have achieved. Here we investigate G. lacustris from areas encompassing a significant portion of its Nearctic range, with the goal of examining its phylogeographic and biogeographic history. We reconstructed a time-calibrated phylogenetic tree using data from the mitochondrial COI gene for individuals representing 22 localities of the species. From these data, we observed three distinct clades within the species complex, encompassing individuals from the Palearctic, coastal Nearctic, and interior Nearctic, suggesting these as possible dispersal pathways. Additional analyses, incorporating more localities and more genetic information will certainly elucidate more on this species’ biogeographic history and will empower further research on its rapid dispersal throughout North America.
Authors: Malorie Plaugher, Andrew G. Cannizzaro, & David J. Berg
Advisor: David J. Berg, Biology
Graduate Advisor: Andrew Cannizzaro, Biology
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