The macroevolutionary consequences of the association between frugivory and carotenoid-dependent plumage coloration in passerine birds

Biotic interactions influence evolutionary pathways, impacting
diversification positively and negatively. Here, we examine the
coevolutionary dynamics between frugivorous diets and carotenoid-dependent
plumage coloration in passerine birds— a highly diverse order in which
nearly half of species exhibit carotenoids in their plumage. Plumage
coloration is crucial for species recognition and mate choice. As birds
cannot synthesize carotenoids, they must obtain them from the diet. We
analyze data from 90% of passerines and explore correlations between
frugivory, a key carotenoid source, plumage coloration, and
diversification rates.The data used in our study includes binary
classification of passerines based on whether they present
carotenoid-dependent plumage coloration or not and whether fruit compose
50% or more of the diet, also codified as a binary trait. All data come
from published sources. Our Bayesian analysis reveals a strong
evolutionary correlation between frugivory and the presence of carotenoid
plumage coloration. However, Bayesian state-dependent speciation and
extinction models (SSE) showed that neither frugivory nor carotenoid
coloration independently correlate with heightened diversification.
Results are unchanged when we analyze the combination of both traits,
challenging the conventional assumption of increased speciation driven by
frugivory in species with carotenoid-dependent plumage coloration. These
findings underscore the complexity of trait interactions in shaping
evolutionary trajectories and the importance of hidden states in modeling
diversification.