Department of Entomology, University of Arizona, Tucson, AZ.
J Insect Sci. 2020 Jul 1;20(4). doi: 10.1093/jisesa/ieaa080.
For a trait to be considered polymorphic, it must fulfill both genetic and ecological criteria. Genetically, a polymorphic trait must have multiple heritable variants, potentially from the same female, in high-enough frequency as to not be due to mutation. Ecologically, in a single wild population, these variants must co-occur, and be capable of interbreeding. Polymorphism is frequently considered in the context of either geographical cause or genetic consequence. However, the incorporation of both in a single study can facilitate our understanding of the role that polymorphism may play in speciation. Here, we ask if the two color morphs (green and yellow) exhibited by larvae of the whitelined sphinx moth, Hyles lineata (Fabricius), co-occur in wild populations, in what frequencies, and whether they are genetically determined. Upon confirmation from field surveys that the two color morphs do co-occur in wild populations, we determined heritability. We conducted a series of outcrosses, intercrosses and backcrosses using individuals that had exhibited yellow or green as laboratory-reared larvae. Ratios of yellow:green color distribution from each familial cross were then compared with ratios one would expect from a single gene, yellow-recessive model using a two-sided binomial exact test. The offspring from several crosses indicate that the yellow and green coloration is a genetic polymorphism, primarily controlled by one gene in a single-locus, two-allele Mendelian-inheritance pattern. Results further suggest that while one gene primarily controls color, there may be several modifier genes interacting with it.
为了被认为是多态的，一个特征必须同时满足遗传和生态标准。从遗传学上讲，多态性特征必须具有多个可遗传的变体，这些变体可能来自同一个雌性，其出现的频率足够高，不能归因于突变。从生态学上讲，在一个单一的野生种群中，这些变体必须共同存在，并能够杂交。多态性通常是在地理原因或遗传后果的背景下进行考虑的。然而，在单个研究中同时考虑这两个因素可以帮助我们理解多态性在物种形成中可能扮演的角色。在这里，我们询问幼虫的 whitelined sphinx moth（Hyles lineata（Fabricius））是否存在两种颜色形态（绿色和黄色），它们在野生种群中是否共同存在，出现的频率是多少，以及它们是否是由遗传决定的。通过野外调查证实这两种颜色形态确实在野生种群中共同存在，我们确定了遗传力。我们使用在实验室中饲养的幼虫表现出黄色或绿色的个体进行了一系列的杂交、互交和回交。然后，使用双边二项式精确检验，将每个家系杂交的黄色：绿色颜色分布比例与一个单基因、黄色隐性模型的预期比例进行比较。来自几个杂交的后代表明，黄色和绿色的颜色是一种遗传多态性，主要由一个基因控制，该基因位于一个单基因座的两个等位基因孟德尔遗传模式中。结果进一步表明，虽然一个基因主要控制颜色，但可能有几个修饰基因与其相互作用。
