Data from: Macroevolution of Arboreality in Salamanders

Evolutionary theory predicts that selection in distinct microhabitats
generates correlations between morphological and ecological traits, and
may increase both phenotypic and taxonomic diversity. However, some
microhabitats exert unique selective pressures that act as a restraining
force on macroevolutionary patterns of diversification. In this study, we
use phylogenetic comparative methods to investigate the evolutionary
outcomes of inhabiting the arboreal microhabitat in salamanders. We find
that arboreality has independently evolved at least five times in Caudata,
and has arisen primarily from terrestrial ancestors. However, the rate of
transition from arboreality back to terrestriality is 24 times higher than
the converse. This suggests that macroevolutionary trends in microhabitat
use tend towards terrestriality over arboreality, which influences the
extent to which use of the arboreal microhabitat proliferates.
Morphologically, we find no evidence for an arboreal phenotype in overall
body proportions or in foot shape, as variation in both traits overlaps
broadly with species that utilize different microhabitats. However, both
body shape and foot shape display reduced rates of phenotypic evolution in
arboreal taxa, and evidence of morphological convergence among arboreal
lineages is observed. Taken together, these patterns suggest that
arboreality has played a unique role in the evolution of this family,
providing neither an evolutionary opportunity, nor an evolutionary dead
end.