Data from: Unlinked Mendelian inheritance of red and black pigmentation in snakes: implications for Batesian mimicry

Identifying the genetic basis of mimetic signals is critical to understanding both the origin and dynamics of mimicry over time. For species not amenable to large laboratory breeding studies, widespread color polymorphism across natural populations offers a powerful way to assess the relative likelihood of different genetic systems given observed phenotypic frequencies. We classified color phenotype for 2,175 ground snakes (Sonora semiannulata) across the continental United States to analyze morph ratios and test among competing hypotheses about the genetic architecture underlying red and black coloration in coral snake mimics. We found strong support for a two-locus model under simple Mendelian inheritance, with red and black pigmentation being controlled by separate loci. We found no evidence of either linkage disequilibrium between loci or sex linkage. In contrast to Batesian mimicry systems like butterflies in which all color signal components are linked into a single “supergene,” our results suggest that the mimetic signal in colubrid snakes can be disrupted through simple recombination and that color evolution is likely to involve discrete gains and losses of each signal component. Both outcomes are likely to contribute to the exponential increase in rates of color evolution seen in snake mimicry systems over insect systems.阐明拟态信号的遗传基础，对于解析拟态的起源及其随时间推移的动态变化至关重要。针对无法开展大规模实验室繁育研究的物种，自然种群中广泛存在的色彩多态性，为基于观测到的表型频率评估不同遗传系统的相对可能性提供了强有力的研究途径。我们对美国大陆范围内的2175条半纹地蛇（Sonora semiannulata）进行了色彩表型分型，以分析形态比例，并检验关于珊瑚蛇拟态类群红、黑体色背后遗传架构的多项竞争性假说。研究发现，遵循简单孟德尔遗传（Mendelian inheritance）的双位点模型得到了强有力的支持，其中红、黑色素分别由不同的位点调控。未检测到位点间存在连锁不平衡，亦未发现性连锁现象。与蝴蝶这类贝茨拟态（Batesian mimicry）系统中所有色彩信号组分均整合为单个"超基因（supergene）"的情况不同，我们的研究结果表明，游蛇科蛇类（colubrid snakes）的拟态信号可通过简单重组发生解离，且色彩演化大概率涉及各信号组分的独立获得与丢失。这两种结果均可能促成蛇类拟态系统相较于昆虫拟态系统所呈现出的色彩演化速率指数级增长。