Department of Biology, University of Texas, Arlington, TX 76010, USA.
Am Nat. 2013 Aug;182(2):E40-57. doi: 10.1086/670988. Epub 2013 Jun 21.
Color polymorphism in natural populations presents an ideal opportunity to study the evolutionary drivers of phenotypic diversity. Systems with striking spatial, temporal, and qualitative variation in color can be leveraged to study the mechanisms promoting the distribution of different types of variation in nature. We used the highly polymorphic ground snake (Sonora semiannulata), a putative coral snake mimic with both cryptic and conspicuous morphs, to compare patterns of neutral genetic variation and variation over space and time in color polymorphism to investigate the mechanistic drivers of phenotypic variation across scales. We found that strong selection promotes color polymorphism across spatial and temporal scales, with morph frequencies differing markedly between juvenile and adult age classes within a single population, oscillating over time within multiple populations, and varying drastically over the landscape despite minimal population genetic structure. However, we found no evidence that conspicuousness of morphs was related to which color pattern was favored by selection or to any geographic factors, including sympatry with coral snakes. We suggest that complex patterns of phenotypic variation in polymorphic systems may be a fundamental outcome of the conspicuousness of morphs and that explicit tests of temporal and geographic variation are critical to the interpretation of conspicuousness and mimicry.
自然种群中的颜色多态性为研究表型多样性的进化驱动因素提供了理想的机会。具有显著空间、时间和颜色质量变化的系统可以用来研究促进自然中不同类型变异分布的机制。我们使用高度多态的地蛇（Sonora semiannulata），一种具有隐蔽和明显形态的拟珊瑚蛇，来比较中性遗传变异和颜色多态性的空间和时间变化模式，以研究跨尺度表型变异的机制驱动因素。我们发现，强烈的选择促进了跨空间和时间尺度的颜色多态性，同一种群内的幼体和成年年龄类之间的形态频率差异显著，在多个种群内随时间波动，并且尽管种群遗传结构很小，但在景观上差异很大。然而，我们没有发现形态的明显性与选择偏好的哪种颜色模式或任何地理因素（包括与珊瑚蛇的同域性）有关的证据。我们认为，多态系统中复杂的表型变异模式可能是形态明显性的一个基本结果，并且明确测试时间和地理变化对于解释明显性和拟态至关重要。
