Phylogenetic utility of nucleotide sequences of mitochondrial 16S ribosomal RNA and cytochrome b genes in anthocorid bugs (Heteroptera: Anthocoridae)

Nucleotide sequences of portions of the mitochondrial 16S ribosomal RNA gene (16S rDNA) and cytochrome b (cyt b) gene of eight species of the family Anthocoridae and of one outgroup taxon, Nezara viridula (Linnaeus), have been determined. From approximately 428- and 417-base pair aligned sequences of the 16S rDNA and cyt b gene, 185 and 171 variable sites were detected. As reported for some other insect groups, a strong A+T composition bias (78.3%) and A-T transversion bias (54.5% of all nucleotide substitutions) were detected in the 16S rDNA of anthocorid insects. However, in the cyt b gene, A-T transversions (29.2%) were less frequent than T-C transitions (39.8%), even though this gene also contained a relatively high level of A+T (70.7%). In the 16S rDNA, uncorrected genetic divergence increased linearly with an increase in taxonomic level. However, a plateau was observed in the values of the cyt b gene. This tendency was obvious in the third position of codons, in which the values increased very quickly and saturated at the between-subgenus level. These findings suggest that strong multiple substitutions occur in this position. Phylogenetic analyses showed that both the 16S rDNA and cyt b DNA fragments can be used to estimate relationships among anthocorid taxa, even though there are differences between them as regards taxonomic levels at which phylogenetic analysis can be applied.