Ancestral State Reconstruction
We found support for an Ornstein-Uhlenbeck (OU) model (AICc weight = .96), for presence of prealternate molt, but support for Brownian motion (BM) evolution (AICc weight = .60) for extent of prealternate molt. We found support for a BM model for both presence (AICc weight = .56) and extent (AICc weight = .57) of seasonal dichromatism.
The feather regions more involved in prealternate molt, namely the head, breast, belly, and back, showed higher rates of evolution relative to other feather regions (Fig. 4). We reconstructed a partial prealternate molt at the root of the tree, only on the head, with no associated seasonal dichromatism, and several gains and losses of both seasonal dichromatism and prealternate molt (Fig. 4), which agrees with our transition analysis (Fig. 1) that prealternate molt can be gained and lost over time, over separate lineages (Fig. 1e).