CONGRUENCE AND PHYLOGENETIC REANALYSIS OF PERCHING BIRD CYTOCHROME-B SEQUENCES

In a study of the phylogenetic relationships among perching bird mtDNA sequences, Edwards et al. (1991; Proc. R. Soc. London Ser B. 243: 99- 107) sequenced part of the mitochondrial cytochrome b gene from 13 per ching birds (Passeriformes) and a woodpecker outgroup. However, recent ly the validity of part of the sequence of the hermit thrush (Catharus guttatus) in that study has been questioned. To determine the effect of inclusion of this apparently chimeric sequence on the conclusions o f the original analysis, we reanalyzed these sequences using a differe nt published hermit thrush sequence. In addition, we applied tests of congruence to examine the possibility that the abberant phylogenetic b ehavior of chimeric mtDNA sequences might be detected. The reanalysis confirms the ability of slow evolving first and second codon positions of cytochrome b sequences to resolve deep branches in the avian tree. The fact that the new data set does not reject the DNA hybridization tree of these species probably indicates poor ability of the cytochrom e b sequences to discriminate among alternative trees, rather than con sistency among data sets. Statistical testing of trees based on indivi dual amplified segments of mtDNA indicates that congruence tests may b e one useful way of identifying chimeric mtDNA sequences when they hav e not been detected in the laboratory or during standard phylogenetic analysis. (C) 1997 Academic Press.