Phylogeny of Greya (Lepidoptera: Prodoxidae), based on nucleotide sequence variation in mitochondrial cytochrome oxidase I and II: congruence with morphological data

The phylogeny of Greya Busck (Lepidoptera: Prodoxidae) was inferred fromnucleotide sequence variation across a 765-bp region in the cytochromeoxidase I and II genes of the mitochondrial genome. Most parsimoniousrelationships of 25 haplotypes from 16 Greya species and two outgroupgenera (Tetragma and Prodoxus) showed substantial congruence with thespecies relationships indicated by morphological variation. Differencesbetween mitochondrial and morphological trees were found primarily in thepositions of two species, G. variabilis and G. pectinifera, and in thebranching order of the three major species groups in the genus. Conflictsbetween the data sets were examined by comparing levels of homoplasy incharacters supporting alternative hypotheses. The phylogeny of Greyaspecies suggests that host-plant association at the family level and larvalfeeding mode are conservative characters. Transition/transversion ratiosestimated by reconstruction of nucleotide substitutions on the phylogenyhad a range of 2.0-9.3, when different subsets of the phylogeny were used.The decline of this ratio with the increase in maximum sequence divergenceamong taxa indicates that transitions are masked by transversions alongdeeper internodes or long branches of the phylogeny. Among transitions,substitutions of A-->G and T-->C outnumbered their reciprocalsubstitutions by 2-6 times, presumably because of the approximately 4:1(77%) A+T-bias in nucleotide base composition. Of all transversions,73%-80% were A<-->T substitutions, 85% of which occurred at thirdpositions of codons; these estimates did not decrease with an increase inmaximum sequence divergence of taxa included in the analysis. The highfrequency of A<-->T substitutions is either a reflection or anexplanation of the 92% A+T bias at third codon positions.