| Biogeographic patterns were investigated within a single species and among its congenerics. Smallmouth bass (Micropterus dolomieu) were characterized by portions of the cytochrome b gene and the control region although bass in Lake Erie were also evaluated using eight nDNA microsatellites. Overall, little population structure was observed among sites in Lake Erie which was surprising given that most male smallmouth bass exhibit nest site fidelity. But, these lake bass were divergent from bass residing in nearby tributaries indicating that lacustrine bass are reproductively isolated from riverine bass even though both groups may spawn in the same rivers. Adjacent riverine populations have also diverged from each other.; Smallmouth bass from 71 sampling sites spanning their native distribution were analyzed to examine post-glaciation colonizing routes from glacial refugia into the Great Lakes. Phylogenetic analyses indicated that ancestral haplotypes exist in today's Interior and Eastern Highlands, and the tree structure supported sequential colonization events northward with a loss of diversity in more distant populations. Western rivers and the upper Great Lakes were characterized by one phylogroup that was distinct from bass occupying the Ouachita Highlands. Bass from Lake Ontario, Georgian Bay, and the St. Lawrence River were characterized largely by just a single, derived haplotype of unknown geographical origin. The two central lakes, Huron and Erie, were composed of multiple phylogroups indicating numerous source populations and access routes.; The unique biogeography of smallmouth bass and its congenerics ( Micropterus, Centrarchidae) was addressed using comparative morphology to complement the molecularly based phylogeographic component. The genus's greatest diversity is centered in the southeastern USA although several outliers are restricted to watersheds in Texas or the Interior Highlands. Myological variation was quantified for all black bass, but characters suitable for phylogenetic analysis were minimal. Observed variation was characterized primarily as unique abnormalities, often within a single specimen, or mimicking variants that were shared irregularly among species. The lack of significant myological variation may be correlated with the low degree of ecological, anatomical, and life history diversity among black bass. Because black bass displayed myological stasis, they should be excellent outgroups in higher-level systematic analyses of perciform fishes. |
