Data from: Rate of evolutionary change in cranial morphology of the marsupial genus Monodelphis is constrained by the availability of additive genetic variation

We tested the hypothesis that the rate of marsupial cranial evolution is
dependent on the distribution of genetic variation in multivariate space.
To do so, we carried out a genetic analysis of cranial morphological
variation in laboratory strains of Monodelphis domestica and used
estimates of genetic covariation to analyze the morphological
diversification of the Monodelphis brevicaudata species group. We found
that within-species genetic variation is concentrated in only a few axes
of the morphospace and that this strong genetic covariation influenced the
rate of morphological diversification of the brevicaudata group, with
between-species divergence occurring fastest when occurring along the
genetic line of least resistance. Accounting for the geometric
distribution of genetic variation also increased our ability to detect the
selective regimen underlying species diversification, with several
instances of selection only being detected when genetic covariances were
taken into account. Therefore, this work directly links patterns of
genetic covariation among traits to macroevolutionary patterns of
morphological divergence. Our findings also suggest that the limited
distribution of Monodelphis species in morphospace is the result of a
complex interplay between the limited dimensionality of available genetic
variation and strong stabilizing selection along two major axes of genetic
variation.