Phylogeny of Cryptocercus Species (Blattodea: Cryptocercidae) Inferred from Nuclear Ribosomal DNA

Abstract

The wood-feeding cockroaches of the genus Cryptocercus occur in temperate forests. Of the seven known species, five occur in the United States and two in Eurasia. Until 1997, all populations in the United States were considered a single species. Populations in the western United States were elevated to a species status based on variation in DNA sequence and morphology. In 1999, three new species were described from the eastern United States based on variation in chromosome number and mitochondrial DNA, bringing the number of species in the United States to five. The objective of this study was to determine if the DNA sequence of nuclear rRNA also signals the existence of four species in the eastern United States and to compare the inferred relationships with those proposed based on mitochondrial sequences. We obtained the DNA sequence from a portion of the 5.8S and 28S rRNA genes and the entire ITS2 region from 38 individuals and 30 additional clones to assess intraindividual, intraspecific, and interspecific variation. We found extensive sequence variation among the various species and little or no intraindividual and intraspecific variation. Phylogenetic analysis indicated the existence of monophyletic lineages among the eastern United States samples, which largely corresponded to the four species previously described. The inferred relationships were well-supported by bootstrap analysis and decay indices. Although the nuclear rRNA sequences resulted in a coherent phylogenetic tree, the ITS2 region contained many insertions and deletions, which may introduce homoplasy and ambiguity in alignment as more taxa are added to the data set.