Calede Jonathan J M, Brown Andrew
Department of Evolution, Ecology, and Organismal Biology, The Ohio State University, 318 W. 12th Ave., 300 Aronoff Laboratory, Columbus, OH 43210, USA and.
The Ohio State University at Marion, 1459 Mount Vernon Avenue, Marion, OH 43302, USA.
Curr Zool. 2021 Aug 25;68(4):469-488. doi: 10.1093/cz/zoab070. eCollection 2022 Aug.
Geomyoid rodents provide a great study system for the analysis of sexual dimorphism. They are polygynic and many inhabit harsh arid environments thought to promote sexual dimorphism. In fact, there has been extensive work published on the sexual size dimorphism of individual populations and species within this rodent clade. However, little work has been undertaken to assess the evolutionary patterns and processes associated with this sexual dimorphism. We use multivariate analyses of cranial measurements in a phylogenetic framework to determine the distribution of size and shape dimorphism among geomyoids and test for Rensch's rule. Our results suggest that sexual dimorphism is more common in geomyids than heteromyids, but it is not in fact universal. There is evidence for variation in sexual dimorphism across populations. Additionally, in many taxa, geographic variation appears to overwhelm existing sexual dimorphism. We find support for the repeated independent evolution of shape and size dimorphism across geomyoid taxa, but we do not find support for an association between size and shape dimorphism. There is no evidence for Rensch's rule in geomyoids, whether at the superfamily or family level. Together, our findings suggest that there is no single explanation for the evolution of sexual dimorphism in geomyoids and that, instead, it is the product of numerous evolutionary events. Future studies incorporating phylogenetic relationships will be necessary to paint a more complete picture of the evolution of sexual dimorphism in geomyoids.
囊鼠类啮齿动物为分析两性异形提供了一个很好的研究系统。它们是一夫多妻制的，许多栖息在被认为会促进两性异形的恶劣干旱环境中。事实上，关于这个啮齿动物类群中各个种群和物种的两性体型差异，已经发表了大量的研究成果。然而，很少有人致力于评估与这种两性异形相关的进化模式和过程。我们在系统发育框架下对颅骨测量数据进行多变量分析，以确定囊鼠类中体型和形状差异的分布，并检验伦施法则。我们的结果表明，两性异形在囊鼠科中比更格卢鼠科中更为常见，但实际上并非普遍存在。有证据表明不同种群之间的两性异形存在差异。此外，在许多分类群中，地理变异似乎掩盖了现有的两性异形。我们发现支持囊鼠类分类群中形状和体型差异的反复独立进化，但我们没有发现体型和形状差异之间存在关联的证据。在囊鼠类中，无论是在超科还是科级水平上，都没有伦施法则的证据。总的来说，我们的研究结果表明，对于囊鼠类两性异形的进化没有单一的解释，相反，它是众多进化事件的产物。未来纳入系统发育关系的研究将有必要更全面地描绘囊鼠类两性异形的进化情况。
