Correlations of Life-History and Distributional-Range Variation with Salamander Diversification Rates: Evidence for Species Selection

Evolutionary biologists have long debated the relative influence of species selection on evolutionary patterns. As a test, we apply a statistical phylogenetic approach to evaluate the influence of traits related to species distribution and life-history characteristics on patterns of diversification in salamanders. We use independent contrasts to test trait-mediated diversification while accommodating phylogenetic uncertainty in relationships among all salamander families. Using a neontological data set, we find several species-level traits to be variable, heritable, and associated with differential success (i.e., higher diversification rates) at higher taxonomic categories. Specifically, the macroecological trait of small geographic-range size is strongly correlated with a higher rate of net diversification. We further consider the role that plasticity in life-history traits appears to fulfill in macroevolutionary processes of lineage divergence and durability. We find that pedotypy-wherein some, but not all, organisms of a species mature in the gilled form without metamorphosing-is also associated with higher net diversification rate than is the absence of developmental plasticity. Often dismissed as an insignificant process in evolution, we provide direct evidence for the role of species selection in lineage diversification of salamanders.