Species-specific allozyme markers for Appalachian wood-feeding cockroaches (Dictyoptera: Cryptocercidae)

Members of the genus Cryptocercus are wood-feeding cockroaches that live in the temperate forests. Nine species are recognized in the genus worldwide: two in eastern Eurasia, two in China, and five in the United States. Within the United States, one species occurs in the Pacific Northwest and four occur in the Appalachian Mountains. Previous studies have revealed the presence of potential zones of overlap in distribution among the Appalachian species, raising the possibility of hybridization among them. Differences in mitochondrial DNA have previously been identified for the Appalachian species. However, to identify hybrid individuals one or more species-specific, codominant nuclear markers are required. Therefore, our objective was to undertake allozyme analysis of enzymatic loci to identify fixed, species-specific alleles for the four Appalachian species. We assayed a mean of 42 individuals each from 16 sites for allozyme variation for the four species. At 6 of the 33 loci examined, fixed alternate alleles were identified; a combination of 2 loci enabled the identification of all four species. To identify hybrids in the field, we examined 42 individuals each from 13 sites in which two or more of the above species occur in close proximity for presence of heterozygous individuals at one or more of the six fixed loci. No heterozygous individuals were found suggesting the lack of hybridization among the Appalachian species.