Mitochondrial DNA variation and identification of bark weevils in the Pissodes strobi species group in western Canada (Coleoptera: Curculionidae)

Morphological, allozyme, and chromosomal characters and ecological traits have limited value for discriminating among four closely related Pissodes spp. known from western Canada. We amplified a 1585-bp segment of mitochondrial DNA (mtDNA), including half of the cytochrome oxidase I (COI) and all of the tRNA leucine and COII genes, using the polymerase chain reaction, and studied mtDNA variation within and among all four species of Pissodes with restriction enzymes. Twenty-four haplotypes were found among the 121 maternal lineages surveyed. Haplotype distributions suggest intermediate levels of gene flow for each species. Interspecific estimated sequence divergences ranged from 0 to 28.7%. Phylogenetic relationships among species were reconstructed using P. affinis Randall as an outgroup. Pissodes terminalis Hopping and P. nemorensis Germar were the most closely related species, and this clade was most closely related to P. strobi (Peck); P. schwarzi Hopkins branched off below these three. Restriction site variation is sufficient to discriminate unambiguously among most species. However, P, terminalis and P. nemorensis haplotypes were very similar, which may complicate discrimination between these two species, using mtDNA characters, where their ranges putatively overlap in Manitoba. A diagnostic protocol using three restriction enzymes, Eel I, Dra I, and HinfI, is recommended.