Electrophoretic studies of cockroaches of the Australian endemic subfamily Geoscapheinae

Abstract

Abstract Protein electrophoresis was used to investigate the systematics of cockroaches of the Australian endemic subfamily Geoscapheinae. All morphologically-recognized taxa are genetically distinguishable. Indeed, the electrophoretic data suggest that several species ( M. rhinoceros, G. dilatatus and, possibly, M. monteithi ) comprise more than one genetic taxon. Some species ( M. heppleorum and G. robustus ) have high levels of intra-specific variation, possibly reflecting regional differentiation in broad distributions. Conversely, there are low levels of variation over large areas of some species» distributions, notably in the Murray-Darling basin ( G. robustus and G. dilatatus ). Genetic distances between taxa conflict with the current assignment of species to genera based on the morphological characteristics of tergite margins. Where this is the case, the genetic data are in accord with expectations based on geographical proximity and other morphological characters. For instance, the members of the genetic sister groups Neogeoscapheus dahmsi Roth and Parapanesthia pearsoni Walker, Rugg and Rose, and P. gigantea (Tepper) and M. saxicola Walker, Rugg and Rose are geographically very near neighbours. The Northern and inland species of Macropanesthia are found in a Geoscapheus cluster comprising their nearest geographical neighbours rather than with the central and southern Queensland Macropanesthia . Genetic distances are concordant with the presence or absence of an oothecal membrane and the degree of elaboration of male genitalia in geoscapheine species. The level of genetic and taxonomic diversity among the Geoscapheinae near the borders of the subfamily's range in south-eastern Queensland is striking. A Nei unbiased distance of almost 0.80 is required to encompass all 13 morphospecies in the area within a cluster, whereas the most divergent species in the entire Geoscapheinae are separated by a distance of about 1.05.