Patterns of genetic differentiation in appalachian desmognathine salamanders

Abstract

Studies of allozymic variation in salamanders of the Desmognathus ochrophaeus complex have revealed complex patterns of genetic fragmentation among populations and species. Populations of D. carolinensis within the Black and Great Craggy Mountains of western North Carolina exhibit pronounced variation in allozyme frequencies at five polymorphic loci. Allozyme frequencies at one of these loci vary with elevation. There are no obvious patterns at the remaining loci with respect to elevation, latitude, or longitude, and only a weak suggestion of isolation by distance among populations. On a broader geographic scale, the northernmost form (D. ochrophaeus) exhibits very little intrademic variation, even over distances approaching 1000 km. Forms with progressively more southern distributions exhibit progressively higher levels of isolation by distance. Genetic distances among local populations of the more southern forms (D. orestes, D. carolinensis, and D. ocoee) increase with geographic distances among populations separated by less than 100 km, but level off at greater geographic distances. Genetic distances for interspecific comparisons also correlate positively with geographic distances, but the relationships are not oriented toward the origins of the scatterplots, indicating additional genetic differentiation that cannot be attributed to isolation by distance. Patterns of interspecific differentiation do not relate to either geographic or cladistic relationships among these forms. Levels of genetic fragmentation appear higher in southern Appalachian forms of the D. ochrophaeus complex than in two larger, more aquatic congeners: D. monticola and D. fuscus. Biotic interactions with these and other low-elevation predators and competitors may have produced genetic fragmentation in the D. ochrophaeus complex.