Reconstructing Plumage Evolution in Orioles (Icterus): Repeated Convergence and Reversal in Patterns

Abstract

Several empirical studies suggest that sexually selected characters, including bird plumage, may evolve rapidly and show high levels of convergence and 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 number of signal characters. We scored the appearance of 44 adult male plumage characters that varied across New World orioles (Icterus). We mapped the plumage characters onto a molecular phylogeny based on two mitochondrial genes. Reconstructing the evolution of these characters revealed evidence of convergence or reversal in 42 of the 44 plumage characters. No plumage character states are restricted to any groups of species higher than superspecies 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 overall consistency index (CI = 0.28). We found similar results when we mapped plumage changes onto a total evidence tree. Our findings reveal that plumage patterns and colors are highly labile between species of orioles, but highly conserved within the oriole genus. Furthermore, there are at least two overall plumage types that have convergently evolved repeatedly in the three oriole clades. This overall convergence leads to significant conflict between the molecular and plumage data. It is not clear what evolutionary processes lead to this homoplasy in individual characters or convergence in overall pattern. However, evolutionary constraints such as developmental limitations and genetic correlations between characters are likely to play a role. Our results are consistent with the belief that avian plumage and other sexually selected characters may evolve rapidly and may exhibit high homoplasy. The overall convergence in oriole plumage patterns is an interesting evolutionary phenomenon, but it cautions against heavy reliance on plumage characters for constructing phylogenies.

Plumage Convergence in Picoides Woodpeckers Based on a Molecular Phylogeny, With Emphasis on Convergence in Downy and Hairy Woodpeckers

“…Furthermore, plumage patterns that are sexually selected (Burns 1998) may be driven by genetic expression but may also be influenced by hormonal changes or environmentally induced developmental changes. Thus, plumage characters are considered highly labile and of dubious value for phylogenetic analysis (Christidis et al 1988, Hackett and Rosenberg 1990, Kusmierski et al 1997, Omland and Lanyon 2000, but see Livezey 1991, Prum 1997, Chu 1998. Perhaps the greatest difficulty with Short's (1971) evaluation of character evolution in Picoides woodpeckers is the lack of independence between the character data under study and the data used to reconstruct the phylogenetic framework.…”

Genetics, development and evolution of adaptive pigmentation in vertebrates

“…Observations of several different species of blanched and melanic animals ranging from lizards to pocket mice inhabiting the Tularosa Basin provide a dramatic example of convergent evolution over a broad taxonomic scale (Figure 3). Independent evolution of pigmentation and pattern has been observed in many vertebrate species, including poison frogs (Vences et al, 2003), orioles (Omland and Lanyon, 2000), cavefish (Strecker et al, 2003) and cichlid fish (Allender et al, 2003), and provides exciting opportunities to ask whether the same or different genes are responsible for convergent phenotypes.…”

Plumage based classification of the bowerbird genus Sericulus evaluated using a multi-gene, multi-genome analysis

“…The pattern of plumage coloration on the other hand, is likely to be highly genetically determined, and possibly less likely to evolve in a labile manner. Contradictory evidence though suggests plumage coloration is suggested to evolve rapidly (Haavie et al, 2000;Lande, 1981;Omland and Lanyon, 2000). We therefore tested whether general patterns of plumage coloration, i.e.…”