Instituto de Ciencias Ambientales y Evolutivas, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Región de los Ríos, Chile.
Colección de Mamíferos, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Región de los Ríos, Chile.
PeerJ. 2023 Apr 14;11:e15200. doi: 10.7717/peerj.15200. eCollection 2023.
The relationship between phenotypic variation and landscape heterogeneity has been extensively studied to understand how the environment influences patterns of morphological variation and differentiation of populations. Several studies had partially addressed intraspecific variation in the sigmodontine rodent , focusing on the characterization of physiological aspects and cranial variation. However, these had been conducted based on geographically restricted populational samples, and in most cases, the aspects characterized were not explicitly contextualized with the environmental configurations in which the populations occurred. Here, the cranial variation of . was characterized by recording twenty cranial measurements in 235 individuals from 64 localities in Argentina and Chile, which widely cover the geographic and environmental distribution of this species. The morphological variation was analyzed and ecogeographically contextualized using multivariate statistical analyses, which also included climatic and ecological variation at the localities where the individuals were sampled. Results indicate that the cranial variation of this species is mostly clustered in localized patterns associated to the types of environments, and that the levels of cranial differentiation are higher among the populations from arid and treeless zones. Additionally, the ecogeographical association of cranial size variation indicate that this species does not follow Bergmann's rule and that island populations exhibit larger cranial sizes compared to their continental counterparts distributed at the same latitudes. These results suggest that cranial differentiation among the populations of this species is not homogeneous throughout its geographic distribution, and that the patterns of morphological differentiation are also not completely consistent with the patterns of genetic structuring that have been described recently. Finally, the analyses performed to ponder morphological differentiation among populations suggest that the contribution of genetic drift in the formation of these patterns can be ruled out among Patagonian populations, and that the selective effect imposed by the environment could better explain them.
形态变异与景观异质性之间的关系已经得到了广泛的研究，以了解环境如何影响形态变异模式和种群的分化。一些研究已经部分解决了沙鼠科啮齿动物的种内变异问题，重点研究了生理特征和颅骨变异。然而，这些研究都是基于地理上有限的种群样本进行的，而且在大多数情况下，所描述的特征并没有明确地与种群所处的环境配置联系起来。在这里，我们通过记录 235 只个体的 20 个头骨测量值，对来自阿根廷和智利 64 个地点的 进行了颅骨变异特征描述，这些地点广泛覆盖了该物种的地理和环境分布。我们使用多元统计分析方法对形态变异进行了分析和生态地理背景分析，这些分析还包括了个体采样地点的气候和生态变化。结果表明，该物种的颅骨变异主要集中在与环境类型相关的局部模式中，并且在干旱和无树地区的种群中，颅骨分化水平更高。此外，颅骨大小变异的生态地理关联表明，该物种不符合伯格曼法则，并且岛屿种群的颅骨大小比分布在相同纬度的大陆种群更大。这些结果表明，该物种的种群之间的颅骨分化在其地理分布范围内并不均匀，形态分化模式也不完全与最近描述的遗传结构模式一致。最后，对种群之间形态分化的分析表明，可以排除遗传漂变在巴塔哥尼亚种群中形成这些模式的贡献，而环境的选择效应可以更好地解释它们。
