Glimm Tilmann, Kiskowski Maria, Moreno Nickolas, Chiari Ylenia
Department of Mathematics, Western Washington University, Bellingham, WA, United States of America.
Department of Mathematics and Statistics, University of South Alabama, Mobile, AL, United States of America.
PeerJ. 2021 Sep 10;9:e11829. doi: 10.7717/peerj.11829. eCollection 2021.
Animal color patterns are widely studied in ecology, evolution, and through mathematical modeling. Patterns may vary among distinct body parts such as the head, trunk or tail. As large amounts of photographic data is becoming more easily available, there is a growing need for general quantitative methods for capturing and analyzing the full complexity and details of pattern variation. Detailed information on variation in color pattern elements is necessary to understand how patterns are produced and established during development, and which evolutionary forces may constrain such a variation. Here, we develop an approach to capture and analyze variation in melanistic color pattern elements in leopard geckos. We use this data to study the variation among different body parts of leopard geckos and to draw inferences about their development. We compare patterns using 14 different indices such as the ratio of melanistic versus total area, the ellipticity of spots, and the size of spots and use these to define a composite distance between two patterns. Pattern presence/absence among the different body parts indicates a clear pathway of pattern establishment from the head to the back legs. Together with weak within-individual correlation between leg patterns and main body patterns, this suggests that pattern establishment in the head and tail may be independent from the rest of the body. We found that patterns vary greatest in size and density of the spots among body parts and individuals, but little in their average shapes. We also found a correlation between the melanistic patterns of the two front legs, as well as the two back legs, and also between the head, tail and trunk, especially for the density and size of the spots, but not their shape or inter-spot distance. Our data collection and analysis approach can be applied to other organisms to study variation in color patterns between body parts and to address questions on pattern formation and establishment in animals.
动物的颜色模式在生态学、进化领域以及通过数学建模都得到了广泛研究。模式可能在不同的身体部位（如头部、躯干或尾部）有所不同。随着大量的摄影数据变得越来越容易获取，对于捕获和分析模式变异的全部复杂性和细节的通用定量方法的需求也在不断增长。关于颜色模式元素变异的详细信息对于理解模式在发育过程中是如何产生和确立的，以及哪些进化力量可能限制这种变异是必要的。在这里，我们开发了一种方法来捕获和分析豹纹守宫黑化颜色模式元素的变异。我们使用这些数据来研究豹纹守宫不同身体部位之间的变异，并对它们的发育进行推断。我们使用14种不同的指标（如黑化面积与总面积的比率、斑点的椭圆度以及斑点的大小）来比较模式，并使用这些指标来定义两种模式之间的综合距离。不同身体部位模式的存在与否表明了从头部到后腿的模式确立的清晰路径。再加上腿部模式与身体主要模式之间个体内的相关性较弱，这表明头部和尾部的模式确立可能与身体的其他部分无关。我们发现，不同身体部位和个体之间，模式在斑点的大小和密度方面变化最大，但平均形状变化很小。我们还发现两条前腿以及两条后腿的黑化模式之间存在相关性，头部、尾部和躯干之间也存在相关性，特别是在斑点的密度和大小方面，但在形状或斑点间距离方面不存在相关性。我们的数据收集和分析方法可以应用于其他生物体，以研究身体部位之间颜色模式的变异，并解决关于动物模式形成和确立的问题。
