Genomic data reveal similar genetic differentiation between species with vastly different dispersal capabilities and life histories

Little is known about the life histories, population connectivity, or dispersal mechanisms of shallow groundwater organisms. Here we used RAD-seq to analyze population structure in two aquifer species: Paraperla frontalis, a stonefly with groundwater larvae and aerial adults, and Stygobromus sp., a groundwater-obligate amphipod. We found similar levels of connectivity in each species between floodplains separated by ~70 river km in the Flathead River basin of NW Montana, USA. Given that Stygobromous lacks the aboveground life stage of P. frontalis, our findings suggest that aquifer-obligate species might have previously unrecognized dispersal capacity.