Conflict between Amino Acid and Nucleotide Characters.

Slowly evolving characters, such as amino acids and replacement substitutions, have generally been favored over faster evolving characters for inferring phylogenetic relationships. However, amino acids constitute composite characters and, because of the degenerate genetic code, are subject to convergence. Based on an analysis of atpB and rbcL in 567 seed plants, we show that silent substitutions may be more phylogenetically informative than replacement substitutions and that artifacts caused by composite characters and/or convergence cause clades on amino acid trees to conflict with nucleotide trees and independent evidence. These findings indicate that coding nucleotide sequences only as amino acid characters for phylogenetic analysis provides little benefit and may yield misleading results.