Periodic glaciation during the Quaternary period shaped the contemporary
riverscape and distribution of freshwater fishes in the Mississippi
River drainage of central North America. The rainbow darter
(Etheostoma caeruleum) is a member of this ichthyofauna and has a
disjunct distribution in glaciated and unglaciated environments west of
the Mississippi River. The aim of this study was to utilize genome-wide
SNP data to compare the population genomic structure of the rainbow
darter in river networks with disparate glacial histories; the Volga
River in the glaciated upper Mississippi River basin and the Meramec
River in the unglaciated Ozark Plateau. Individuals were sampled from
localities within each river system at distances dictated by the
organismal life history and habitat preferences. Riverscape analyses
were performed on three datasets: total combined localities of both
rivers and one for each river independently. The results revealed a
lasting influence of historic glaciation on the population genomic
structure of rainbow darter populations. There was evidence of
population expansion into the glaciated northern region following
glacial retreat. The population genetic signature within the Volga River
did not fit expectations of the stream hierarchy model, but revealed a
pattern of repeated colonization and extirpation due to cyclic
glaciation. The population within the unglaciated Meramec River adhered
to the stream hierarchy model, with a directional order of genetic
diversity based on the life history and habitat preferences of the
species. These results demonstrate the necessity to consider the
geologic and climatic history of a region as well as the life history of
an organism when interpreting spatial genetic patterns.