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....

本研究验证了有袋类动物颅骨演化速率依赖于多变量空间（multivariate space）内遗传变异分布这一假说。为此，我们针对实验室饲养的灰短尾负鼠（Monodelphis domestica）品系的颅骨形态变异开展了遗传分析，并借助遗传协方差（genetic covariation）估计值，解析了短尾负鼠（Monodelphis brevicaudata）物种类群的形态分化过程。研究结果显示，物种种内的遗传变异仅集中于形态空间（morphospace）的少数几类轴线上；这种显著的遗传协方差影响了短尾负鼠物种类群的形态分化速率，当种间分化沿遗传最小阻力轴（genetic line of least resistance）发生时，其分化速度最快。将遗传变异的几何分布特征纳入考量后，我们对物种分化背后选择机制的检测能力也得到增强；部分选择案例仅在考虑遗传协方差的前提下方可被检测到。