Nucleotide sequence variation and phylogenetic utility of the mitochondrial COI fragment in anthocorid bugs (Hemiptera: Anthocoridae)

From 11 strains of seven anthocorid species and one outgroup taxon, Nezara viridula, a portion of the mitochondrial COI gene was sequenced. Pairwise comparisons of nucleotide and inferred amino acid sequences revealed the biased nature of nucleotide substitutions constrained by a coding function of the gene. Among 974 nucleotide substitutions detected in the anthocorid taxa, 80.9% were seen in the third position of codons. In this position, uncorrected nucleotide divergences increased very quickly with the increase of taxonomic levels and reached a plateau at the within-subgenus level. Among nucleotide substitutions in the first position of codons, which accounted for 16.6% of all nucleotide changes, 88.9% have occurred as a T-C transition between triplets within the degenerate codon family encoding leucine. Phylogenetic analysis results suggest that the COI fragment may only be useful for the relationships among closely related taxa within a subgenus.