Reconstructing plumage evolution in orioles (Icterus): Repeated convergence and reversal in patterns

Several empirical studies suggest that sexually selected characters, includ ing bird plumage, may evolve rapidly and show high levels of convergence an d other forms of homoplasy. However, the processes that might generate such convergence have not been explored theoretically. Furthermore, no studies have rigorously addressed this issue using a robust phylogeny and a large n umber of signal characters. We scored the appearance of 44 adult male pluma ge characters that varied across New World orioles (Icterus). We mapped the plumage characters onto a molecular phylogeny based on two mitochondrial g enes. Reconstructing the evolution of these characters revealed evidence of convergence or reversal in 42 of the 44 plumage characters. No plumage cha racter states are restricted to any groups of species higher than superspec ies in the oriole phylogeny. The high frequency of convergence and reversal is reflected in the low overall retention index (RI = 0.66) and the low ov erall consistency index (CI = 0.28). We found similar results when we mappe d plumage changes onto a total evidence tree. Our findings reveal that plum age patterns and colors are highly labile between species of orioles, but h ighly conserved within the oriole genus. Furthermore, there are at least tw o overall plumage types that have convergently evolved repeatedly in the th ree oriole clades. This overall convergence leads to significant conflict b etween the molecular and plumage data. It is not clear what evolutionary pr ocesses lead to this homoplasy in individual characters or convergence in o verall pattern. However, evolutionary constraints such as developmental lim itations and genetic correlations between characters are likely to play a r ole. Our results are consistent with the belief that avian plumage and othe r sexually selected characters may evolve rapidly and may exhibit high homo plasy. The overall convergence in oriole plumage patterns is an interesting evolutionary phenomenon, but it cautions against heavy reliance on plumage characters for constructing phylogenies.