Data from: Seeing spots: quantifying mother-offspring similarity and assessing fitness consequences of coat pattern traits in a wild population of giraffes (Giraffa camelopardalis)

Polymorphic phenotypes of mammalian coat coloration have been important to the study of genetics and evolution, but less is known about the inheritance and fitness consequences of individual variation in complex coat pattern traits such as spots and stripes. Giraffe coat markings are highly complex and variable and it has been hypothesized that variation in coat patterns most likely affects fitness by camouflaging neonates against visually hunting predators. We quantified complex coat pattern traits of wild Masai giraffes using image analysis software, determined the similarity of spot pattern traits between mother and offspring, and assessed whether variation in spot pattern traits was related to fitness as measured by juvenile survival. The methods we described could comprise a framework for objective quantification of complex mammal coat pattern traits based on photographic coat pattern data. We demonstrated that some characteristics of giraffe coat spot shape were likely to be heritable, as measured by mother-offspring regression. We found significant variation in juvenile survival among phenotypic groups of neonates defined by multivariate clustering based on spot trait measurement variables. We also found significant variation in neonatal survival associated with spot size and shape covariates. Larger spots (smaller number of spots) and irregularly shaped spots (smaller aspect ratio) were correlated with increased survival. These findings will inform investigations into developmental and genetic architecture of complex mammal coat patterns and their adaptive value.

哺乳动物毛色的多态表型（Polymorphic phenotypes）一直是遗传学与进化学研究的重要议题，但针对斑点、条纹这类复杂毛色图案性状的个体差异，其遗传规律与适合度后果的相关研究尚不多见。长颈鹿的皮毛斑纹兼具高度复杂性与变异性，此前学界已提出假说：皮毛图案的变异大概率会通过为新生幼崽提供伪装，使其躲避视觉捕食者，进而影响其适合度。本研究借助图像分析软件对野生马赛长颈鹿（Masai giraffes）的复杂皮毛图案性状进行了量化，测定了斑点图案性状在母代与子代间的相似性，并以幼崽存活率作为适合度的衡量标准，评估了斑点图案性状的变异是否与适合度相关。本文所述方法可构建一套基于摄影图像数据的、用于客观量化哺乳动物复杂皮毛图案性状的研究框架。研究通过母子回归分析证实，长颈鹿斑点形状的部分特征具有可遗传性；基于斑点性状测量变量进行多变量聚类所定义的新生个体表型组间，幼崽存活率存在显著差异；同时，斑点大小与形状的协变量也与新生幼崽存活率存在显著关联：更大的斑点（即斑点数量更少）与形状更不规则的斑点（即长宽比更小）均与更高的存活率相关。本研究结果将为后续探索哺乳动物复杂皮毛图案的发育与遗传架构及其适应性价值提供重要研究指引。