Intra-specific pelage color variation in a South American small rodent species

Abstract Intra-specific color variation is often underestimated by researchers, and among mammals, intra-specific differences in coloration are poorly documented for most species. The main goal of this study was to apply an objective color measurement methodology to the study of a specific problem: the detection, if any, of patterns of changes in the fur color of specimens of Akodon budini in relation to biological (i.e., sex) and environmental (i.e., season) variables. We hypothesize that coat color will be more homogeneous in males than in females and that coat color will be darker in winter than in summer, the latter being orange. We measured the pelage color on five points over the dorsal surface of 26 A. budini museum specimens using a spectroradiometer and a diffuse illumination cabin. We used Principal Component Analysis to describe the association between the color variables, sex and season, and each of the observations. We then used general linear models of Analysis of Variance to examine relationships between color data, season, and sex. The results clearly confirm the hypothesis related to seasonal coat color change but do not directly confirm the hypothesis related to changes in coat color in relation to sex, and we show the complexity of the studied pattern. In conclusion, undoubtedly, the studied variables should accordingly be considered when studying the coloration of specimens for characterization, identification and discrimination of different taxonomic units based on color.

摘要 种内体色变异常被研究者低估；在哺乳动物类群中，多数物种的种内体色差异记录均较为匮乏。本研究的核心目标是采用客观的体色测量方法，针对一个具体科学问题展开探究：即检测布迪纳南美原鼠（Akodon budini）标本的皮毛体色变化模式是否与生物学变量（即性别）及环境变量（即季节）相关。本研究提出如下假说：雄性个体的体色相较于雌性更为均一；冬季的体色较夏季更深，而夏季体色呈橙黄色。研究团队使用分光辐射度计（spectroradiometer）与漫照明舱（diffuse illumination cabin），对26件馆藏布迪纳南美原鼠标本的背部体表5个点位进行了体毛颜色测量。本研究采用主成分分析（Principal Component Analysis），以解析体色变量、性别与季节同各观测样本间的关联。随后通过方差分析（Analysis of Variance）的一般线性模型，检验体色数据与季节、性别之间的关联关系。研究结果明确验证了关于季节性体色变化的假说，但未直接证实与性别相关的体色变化假说，同时揭示了本次研究对象体色模式的复杂性。综上，在基于体色对不同分类单元进行特征描述、物种鉴定与类群区分的标本体色研究中，本研究所涉及的变量无疑应当被纳入考量范畴。