Grieco T M, Rizk O T
Department of Integrative Biology, University of California at Berkeley, Berkeley, California 94720, USA.
J Morphol. 2010 Aug;271(8):897-909. doi: 10.1002/jmor.10839.
Environmental variation over a species's range creates differing pressures to which organisms must adjust in order to survive. Taxa can respond to these pressures at population and individual levels, leading to localized phenotypic differentiation. Assessing the spatial distribution of phenotypic variation can illuminate how dramatically varying environmental factors shape phenotypes and may forecast a taxon's ability to adapt should conditions change. We characterized morphological variation along a transect sampled in the Grinnell Resurvey project to determine whether Gambel's white-footed mouse (Peromyscus maniculatus gambelii), a generalist taxon inhabiting the full elevational range of habitats in Yosemite National Park and surrounding areas, has responded morphologically to variation in its environment. We quantified variation in modern P. m. gambelii cranial shape using 2D generalized Procrustes analysis and Euclidean distance matrix-based geometric morphometrics. We performed multivariate regression of shape coordinates on elevation to test for environmental influences on shape within the principal geographic dimension of change along the transect. We observe a statistically significant correlation with shape on elevation for occlusal and lateral views of the cranium, explaining a small percentage of the overall variation in shape. Modern P. m. gambelii crania show a pattern of flexion in which the angle of the cranial base decreases at higher elevations. Results of EDMA parallel these findings, but highlight additional areas of the cranium that vary with elevation. Collectively, the patterns of variation detected suggest a biological response to the environment that warrants further study. This work lays the foundation for comparison with morphological data from historical specimens, which can address evolutionary scenarios generated from our findings, and for investigation of other taxa included in the resurvey project.
一个物种分布范围内的环境变化会产生不同的压力，生物体必须适应这些压力才能生存。分类群可以在种群和个体层面上对这些压力做出反应，从而导致局部表型分化。评估表型变异的空间分布可以阐明环境因素的巨大差异如何塑造表型，并可能预测分类群在条件变化时的适应能力。我们在格里内尔重新调查项目中沿着一条样带对形态变异进行了特征描述，以确定白足鼠（Peromyscus maniculatus gambelii），一种栖息于优胜美地国家公园及周边地区全海拔范围栖息地的泛化分类群，是否在形态上对其环境变化做出了反应。我们使用二维广义普罗克汝斯分析和基于欧几里得距离矩阵的几何形态测量学对现代白足鼠颅骨形状的变异进行了量化。我们对形状坐标与海拔进行多元回归，以测试沿样带主要地理变化维度内环境对形状的影响。我们观察到，颅骨咬合面和侧面视图的形状与海拔之间存在统计学上的显著相关性，解释了形状总体变异的一小部分。现代白足鼠颅骨呈现出一种弯曲模式，即颅底角度在较高海拔处减小。欧几里得距离矩阵分析（EDMA）的结果与这些发现一致，但突出了颅骨中随海拔变化的其他区域。总体而言，检测到的变异模式表明了一种对环境的生物学反应，值得进一步研究。这项工作为与历史标本的形态数据进行比较奠定了基础，这些比较可以解决由我们的发现所产生的进化情景问题，也为重新调查项目中包含的其他分类群的研究奠定了基础。
