Novel polymorphic microsatellite loci for distinguishing rock bass (Ambloplites rupestris), Roanoke bass (Ambloplites cavifrons), and their hybrids

The rock bass (Ambloplites rupestris) is a popular sport-fish native to the Mississippi and Great Lakes basins of North America. The species has been widely introduced outside its native range, including into Atlantic-slope streams of Virginia where it may hybridize with an imperiled, similar-looking congener, the Roanoke bass (Ambloplites cavifrons). In this study, we identified and evaluated novel molecular markers to facilitate identification of these species and study the extent of hybridization. Using molecular libraries developed from A. rupestris, we identified a suite of candidate nuclear microsatellite loci, synthesized primer sets, and tested these markers for amplification and polymorphism in populations of both species. We then calculated standard diversity statistics within and differentiation statistics between species, the latter providing an indication of marker power for distinguishing the species and their hybrids. Additionally, we evaluated our efficiency for identifying hybrids by classifying simulated genotypes of known ancestry. Eleven loci were polymorphic (2-22 alleles per locus) and reliably amplified in both species. Multilocus genetic differentiation between A. cavifrons and A. rupestris was quite high (F ST  = 0.66; D LR  = 19.3), indicating the high statistical power of this marker set for species and hybrid identification. Analyses of simulated data suggested these markers reliably distinguish between hybrids and non-hybrids, as well as between F1 hybrids and backcrossed individuals. This panel of 11 loci should prove useful for understanding patterns of hybridization between A. rupestris and A. cavifrons. As the first microsatellite markers developed for Ambloplites, these markers also should prove broadly useful for population genetic studies of this genus.

Fish faunal provinces of the conterminous United States of America reflect historical geography and familial composition

Although the conterminous USA has a long history of ichthyological exploration, the description of biogeographical provinces has been ad hoc. In this study we quantitatively determined fish faunal provinces and interpreted them in the context of the geological history of North America. We also evaluated influences of major river basin occupancy and contemporary environmental factors on provincial patterns. Our data set comprised 794 native fishes, which we used to generate a presence and absence matrix for U.S. Geological Survey (USGS) four-digit hydrologic units. Three nested data sets were analysed separately: primary freshwater families, continental freshwater families (including primary and secondary families) and all freshwater families (including primary, secondary and peripheral families). We used clustering analysis to delimit faunal breaks and one-way analysis of similarity (ANOSIM) to determine significance among clusters (i.e. provinces). We used an indicator-species analysis to identify species that contributed most to province delineations and a similarity-percentage (SIMPER) analysis to describe the relative influence of representatives from each category (i.e. primary, secondary, peripheral) on provincial boundaries. Lastly, we used a parsimony redundancy analysis to determine the roles of historical (i.e. major river basin) and contemporary environmental factors in shaping provinces. Analysis of the nested data sets revealed lessening provincial structure with inclusion of more families. There were 10 primary freshwater provinces, 9 continental freshwater provinces and 7 all freshwater provinces. Major basin occupancy, but not contemporary environmental factors, explained substantial variance in faunal similarities among provinces. However, provincial boundaries did not conform strictly to modern river basins, but reflected river-drainage connections of the Quaternary. Provinces represent broad-scale patterns of endemism and provide a starting point for future studies. Relative malleability of province boundaries in the continental interior highlights this region as biogeographically diverse and dynamic. Interior-core provinces of this region (Central Gulf Coastal Plains, Northern Interior) have not been recognized previously and warrant further study.

Phylogeography of Pteronotropis signipinnis, P. euryzonus, and the P. hypselopterus Complex (Teleostei: Cypriniformes), with Comments on Diversity and History of the Gulf and Atlantic Coastal Streams

The cyprinid genus Pteronotropis is endemic to southeastern Gulf of Mexico and Atlantic Ocean of North America. Never before has the genus been demonstrated to be monophyletic. We investigate both the phylogenetic relationships and the phylogeography of some species in the genus using mitochondrial ND2 sequences. In no analysis is the genus resolved as monophyletic if Notropis harperi is not included in the genus. Biogeographic and phylogeographic evaluations are conducted with Pteronotropis, including P. signipinnis, P. euryzonus, and the P. hypselopterus complex. Patterns of relationships and population genetic analyses support divergences within multiple clades both at the species level and within species that are tied to abiotic changes in the region. Replicated patterns across clades are observed, as well as patterns previously found in other taxa. Pteronotropis hypselopterus is likely not a natural grouping as populations from some drainages form clades more closely related to other species of the genus. The general patterns of relationships indicate likely cryptic species not currently recognized. Finally, the patterns of species relationships and clades and population structuring within species serve as another example of replicated divergences in the biodiversity east and west of the Mobile Bay.