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).