EVIDENCE FOR SIBLING SPECIES IN CRYPTOCERCUS-PUNCTULATUS, THE WOOD ROACH, FROM VARIATION IN MITOCHONDRIAL-DNA AND KARYOTYPE

The wood-feeding genus Cryptocercus is considered the basal lineage am ong extant cockroaches. Cryptocercus is the sole representative of the family Cryptocercidae and at present three species are recognized wit hin the genus worldwide: Cryptocercus punctulatus in the United States , C. relictus in Eurasia and C. primarius in the Orient. The geographi cal distribution of C. punctulatus in the USA is disjunct, with popula tions occurring along the Appalachian Mountains and in the Pacific Nor th-west. In samples collected from several locations of the eastern an d the western USA, we investigated variation in DNA sequence of portio ns of the two mitochondrial rRNA genes and in chromosome number. The o verall sequence divergence among 30 individuals assayed from 17 locati ons was 17.3 per cent. A phylogenetic analysis revealed that in the ea st, individuals in Virginia had diverged significantly in their haplot ype from those in North Carolina, Georgia and Alabama; individuals in the west (Oregon) had diverged in their haplotype from individuals in the east. The diploid chromosome number for 52 male C. punctulatus sam pled from 15 locations varied from 37 (18(II) + X) to 47 (23(II) + X). In the eastern samples, the diploid chromosome number ranged from 37 to 45, whereas in Oregon all individuals had 2n = 47. No polymorphism in DNA sequence or chromosome number among individuals collected withi n a locality was detected. The DNA sequence and chromosome number vari ation data, together with preliminary studies on mating incompatibilit y, strongly suggest that C. punctulatus in the USA is comprised of at least two and probably three sibling species, with one species occurri ng in western USA and one or more species in eastern USA.