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.解析拟态信号的遗传基础，对于理解拟态的起源及其随时间推移的动态变化至关重要。对于无法开展大规模实验室繁育研究的物种而言，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。我们对分布于美国大陆的2175只地蛇（Sonora semiannulata）进行了色彩表型分型，以分析其形态比例，并检验关于珊瑚蛇拟态类群红黑着色遗传结构的多种竞争性假说。本研究结果强烈支持简单孟德尔遗传（Mendelian inheritance）下的双位点模型：红色与黑色色素分别由不同的基因座调控。未检测到基因座间存在连锁不平衡（linkage disequilibrium），亦未发现伴性遗传（sex linkage）的迹象。与蝴蝶等贝茨拟态（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被打破，且色彩演化大概率涉及各信号组分的独立获得与丢失。这两种演化模式均可能促成蛇类拟态系统中，相较于昆虫拟态系统所观测到的色彩演化速率呈指数级增长的现象。