Gentic Differentiation, Hybridization and Reproductive Isolation in Mygalopsis marki Bailey (Orthoptera: Tettigoniidae)

Abstract

Differentiation between northern and southern populations of M. marki was revealed for the sex- linked enzyme PGM, the autosomal enzyme LGGP, and the number of teeth on the stridulatory file. Northern populations are fixed for the PGMb allele, and possess the LGGPd allele at moderate frequencies, whereas southern populations are fixed for PGMa and lack LGGPd. Northern populations also have lower mean numbers of teeth. A zone of overlap was indicated by two populations polymorphic for PGM. Within these populations, genotypic frequencies for both PGM (in females) and LGGP conform closely with Hardy-Weinberg expectations, implying random mating. Despite this, the unlinked PGM and LGGP are in strong linkage disequilibrium, with LGGPd found only with PGMb. Furthermore, the mean number of teeth is lower in PGMb than in PGMa males in the polymorphic populations. This association of genetically and functionally independent traits indicates that northern and southern gene pools are isolated, and that the area of overlap is a hybrid zone between two sibling species.