COMPARING MOLECULAR EVOLUTION IN 2 MITOCHONDRIAL PROTEIN-CODING GENES(CYTOCHROME-B AND ND2) IN THE DABBLING DUCKS (TRIBE, ANATINI)

Rates of sequence evolution were estimated for the cytochrome b (cyt b ) and NADH dehydrogenase subunit 2 (ND2) genes using a phylogeny of th e dabbling ducks (Tribe: Anatini) and outgroups. This speciose group w as densely sampled, reducing the impact of undetected homoplasy on rat e comparisons. Phylogenies based on sequences of the two gene regions and various weighting schemes differed, but most of the differences in volved weakly supported nodes. In addition, partition homogeneity test s show that these differences were not due to statistically significan t conflict between the data sets. Cyt b and ND2 also showed similar ra tes and types of both nucleotide and amino acid substitutions. For bot h genes, substitutions between isoleucine and valine and between alani ne and threonine were most common; both of these substitution types ar e the result of A-G transitions at first positions of codons, Rates of sequence evolution varied substantially and significantly among nucle otide positions, and even within a given codon position (first, second , or third), rates were significantly heterogeneous among sites. Withi n Anatini, cyt b and ND2 show similar levels of variation and homoplas y, and are equally useful for reconstructing the species level phyloge ny of this group. (C) 1998 Academic Press.