Data from: Macroevolution of body extremities reveals an integrated phenotypic response of coloration and morphology to temperature in a large clade of Neotropical passerines (Furnariida)

Endotherms show smaller extremities (Allen’s rule) and larger body sizes
(Bergmann’s rule) in colder climates, thereby reducing heat loss.
Coloration can also be important in thermoregulation, as darker coloration
absorbs more radiant energy than lighter coloration (Bogert’s rule or
thermal melanism hypothesis). Extremities lacking or bearing thinner
covers of feathers or fur —such as ears, legs and bills— can be important
thermal windows to exchange heat. Yet, no study to date has simultaneously
investigated the coloration and morphology of body extremities in relation
to temperature. In 566 species of Furnariida (Neotropical ovenbirds and
allies), we tested with phylogenetic comparative methods whether body
extremity coloration, morphology and plumage coloration jointly respond to
temperature. We predicted that, in colder climates, bills and tarsi would
be darker and smaller as well as associated with darker plumage and larger
body sizes. Consistent with this prediction, we found that bills are
darker, smaller and are associated with darker plumage and larger body
sizes in colder climates. Tarsi are darker and associated with darker
plumage and larger body sizes in colder climates, but tarsus coloration is
not associated with tarsus length, which, contrary to predictions of
Allen’s rule, was longer in colder climates. Using phylogenetic path
analyses, we found that climate affects body extremity coloration both
directly and indirectly through its effects on habitat type, plumage
coloration and morphology. Our study suggests that temperature promotes an
integrated phenotypic response of coloration and morphology across body
extremities, plumage and body size.