Data from: The ecology of a continental evolutionary radiation: Is the radiation of sigmodontine rodents adaptive?

Evolutionary radiations on continents are less well-understood and
appreciated than those occurring on islands. The extent of ecological
influence on species divergence can be evaluated to determine whether a
radiation was ultimately the outcome of divergent natural selection or
else arose mainly by nonecological divergence. Here, we used phylogenetic
comparative methods to test distinct hypotheses corresponding to adaptive
and nonadaptive evolutionary scenarios for the morphological evolution of
sigmodontine rodents. Results showed that ecological variables (diet and
life-mode) explain little of the shape and size variation of sigmodontine
skulls and mandibles. A Brownian model with varying rates for insectivory
versus all other diets was the most likely evolutionary model. The
insectivorous sigmodontines have a faster rate of morphological evolution
than mice feeding on other diets, possibly due to stronger selection for
features that aid insectivory. We also demonstrate that rapid
early-lineage diversification is not accompanied by high morphological
divergence among subclades, contrasting with island results. The
geographic size of continents permits spatial segregation to a greater
extent than on islands, allowing for allopatric distributions and escape
from interspecific competition. We suggest that continental radiations of
rodents are likely to produce a pattern of high species diversification
coupled with a low degree of phenotypic specialization.