Molecular systematics and evolution of molt and plumage in Cardinalines (Aves: passeriformes: Fringillidae).

Abstract

Adaptive significance of molt and plumage patterns in cardinalines has been the subject of speculation, but evolutionary patterns of molt that is the proximate source of variations in their plumage have not been studied in a historical context. My dissertation research investigates evolution of molt and plumage in first-year cardinalines using a phylogenetic approach. In order to test monophyly of cardinalines, I reconstructed phylogenetic relationships of 44 fringillids that represent the overall diversity of the family, based on 3.2 kb of mitochondrial DNA sequences. The monophyly of Fringillidae and its two constituent subfamilies, Fringillinae and Emberizinae, was consistently supported with a few exceptions. However, the monophyly of Cardinalini (cardinals and grosbeaks), as well as two other tribes, Thraupini (tanagers) and Emberizini (New World sparrows), was not supported. I observed molt and plumage change during the first year of five cardinalines and nine other emberizine species in captivity. All the species studied grow juvenal feathers with two distinct episodes. Cardinalines share a distinct molt that starts a few days after fledging, and the timing of this molt is age dependent unlike seasonally controlled first prebasic molt of other emberizines or definitive prebasic molt in many North American passerines. The variations in timing, extent, and duration of the first prebasic molt appear to reflect the age of the bird and the time window available for the molt. Finally, I reconstructed phylogenetic relationships of cardinalines based on a total of 2.5 kb DNA sequences from both mitochondrial and nuclear genomes and investigated evolutionary patterns of delayed plumage maturation. If delayed plumage maturation is adaptive due to its advantages in avoiding predators and intraspecific competitions, I predict that delayed plumage maturation is likely to evolve in migratory species that experience more behavioral and physiological challenges during the first winter and breeding season. On the contrary to the prediction, the results of phylogenetic analyses indicated that second-year males of migratory species are more likely to attain brighter plumage. The results of this study suggest that delayed plumage maturation has been maintained due to genetic constraints.