Molecular divergence betweenGryllus rubensandGryllus texensis, sister species of field crickets (Orthoptera: Gryllidae)

Abstract

AbstractWe assess the degree of sequence divergence in the maternally inherited mitochondrial cytochromecoxidase I (COI) and cytochromeb(CytB) genes between two sister species of field crickets,Gryllus rubensScudder, 1902 andGryllus texensisCade and Otte, 2000. We analyzed 1460 base pairs from 10 individuals of each species; individuals were sampled from areas of both allopatry and sympatry. Overall average pairwise mitochondrial sequence divergence between species was 1.4% ± 0.1% (mean ± SD); however, there was almost an order of magnitude more divergence in COI (2.59% ± 2.25%) than in CytB (0.35% ± 0.24%).Gryllus texensisappears to harbor a much greater level of genetic variation than doesG. rubens. Phylogenetic trees constructed from these sequences show reasonable separation of species; however, sequences are not reciprocally monophyletic. Gene tree polyphyly may reflect recent species-level divergence and (or) interspecific gene flow. The pattern of sequence divergence and genetic variation in these taxa is consistent with allopatric or peripatric speciation in Pleistocene glacial refugia in the southeastern (G. rubensancestral lineage) and southcentral United States (G. texensisancestral lineage).