Evolution of Brown Towhees: Mitochondrial DNA Evidence

Mitochondrial DNA (mtDNA) differentiation was studied among members of the Brown Towhee complex, Pipilo albicollis, P. aberti, P. fuscus, and P. crissalis. Using 16 restriction endonucleases, 196 fragments and 119 sites were observed, and an average interspecific sequence divergence of 6.4% was estimated. There was little geographic differentiation between Baja California and California samples of crissalis or between California and Arizona samples of aberti. Using phylogenetic procedures, it was shown that aberti and crissalis are sister taxa, as predicted by Davis (1951). Allozyme and mtDNA data clearly support the species distinction of crissalis and fuscus. The relationship between albicollis and fuscus, viewed as sister taxa by Zink (1988) based on allozymes, is supported albeit not strongly by the mtDNA data. MtDNA and allozyme data reveal similar patterns of evolutionary history within this group.