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.

我们验证了如下假说：有袋类动物的颅骨演化速率，取决于多变量空间中遗传变异的分布格局。为此，我们针对实验室品系灰短尾负鼠（Monodelphis domestica）的颅骨形态变异开展了遗传分析，并基于遗传协变估计量，解析了短尾负鼠物种组（Monodelphis brevicaudata）的形态多样化过程。研究发现，物种种内的遗传变异仅集中于形态空间的少数几个维度轴上，且这种强烈的遗传协变会影响短尾负鼠物种组的形态多样化速率：当物种间分化沿遗传最小阻力路径（genetic line of least resistance）进行时，分化速度最快。纳入遗传变异的几何分布特征后，我们对物种多样化背后选择机制的检测能力也得到增强——部分选择实例仅在考虑遗传协变因素时才能被识别。因此，本研究直接将性状间的遗传协变格局与宏观进化层面的形态分化模式建立了关联。我们的研究结果还表明，短尾负鼠属物种在形态空间中的分布局限，源于可用遗传变异的维度限制，与沿遗传变异两大主要轴的强烈稳定选择之间的复杂相互作用。