Distribution of Karyotypes of the <I>Cryptocercus punctulatus</I> Species Complex (Dictyoptera: Cryptocercidae) in the Southern Appalachians: Relation to Habitat and History

Abstract

The distributional pattern of the four known karyotypes (male 2n = 37, 39, 43, 45) of the Cryptocercus punctulatus Scudder species complex is reported, based on 71 sites in the Southern Appalachian Mountains with an emphasis on western North Carolina. Populations with different karyotypes are geographically structured in a mosaic, with at least one karyotype occurring in two disjunct regions. Abrupt geographic transitions between karyotypes suggest a parapatric distribution. We found no overlap in the distribution of the different karyotypes, as recently suggested. Although the boundary zones between karyotypes do not appear to coincide with physical or ecological barriers to dispersal, several transitions between karyotypes occur on or near the highest mountains in the southern Appalachians. We suggest that the different karyotypes arose by vicariance, with current boundaries formed by secondary contact when populations isolated in glacial refugia subsequently spread into high-mountain habitats. Because of their dependence on mature mesic forests, populations of the cockroach likely advance up and down mountainsides in cycles of advances and retreats dictated by climatic oscillations that raise and lower the timberline. We discuss the taxonomic status of the different karyotype groups in the C. punctulatus complex, and conclude that more exacting evidence is required to establish if species-level status is warranted. The conclusions of certain earlier studies are weak because, among other things, karyology was not examined in the sampled specimens, including those designated as types.