Department of Biology, Shinshu University, Matsumoto, Japan.
J Evol Biol. 2010 Nov;23(11):2377-84. doi: 10.1111/j.1420-9101.2010.02099.x. Epub 2010 Sep 6.
Development is left-right reversed between dextral and sinistral morphs of snails. In sympatry, they share the same gene pool, including polygenes for shell shape. Nevertheless, their shell shapes are not the mirror images of each other. This triggered a debate between hypotheses that argue either for a developmental constraint or for zygotic pleiotropic effects of the polarity gene. We found that dextrals can be wider or narrower than sinistrals depending on the population, contrary to the prediction of invariable deviation under a developmental constraint. If the pleiotropy is solely responsible instead, the mean shape of each morph should change, depending on the frequency of polarity genotype. Our simulations of this mean shape change under zygotic pleiotropy, however, show that the direction of interchiral difference remains the same regardless of genotype frequency. Our results suggest the presence of genetic variation among populations that changes the maternal or zygotic pleiotropic effect of the polarity gene.
在右旋和左旋蜗牛形态之间，发育是左右反转的。在同域中，它们共享相同的基因库，包括壳形状的多基因。然而，它们的壳形状并不是彼此的镜像。这引发了一场争论，争论的焦点是在发育约束假说或极性基因的合子多效性假说之间进行选择。我们发现，右旋蜗牛可以比左旋蜗牛更宽或更窄，这取决于种群，这与发育约束下不变偏差的预测相反。如果多效性是唯一的原因，那么每个形态的平均形状应该根据极性基因型的频率而发生变化。然而，我们对合子多效性下这种平均形状变化的模拟表明，无论基因型频率如何，手性差异的方向保持不变。我们的结果表明，种群之间存在遗传变异，这种遗传变异改变了极性基因的母体或合子多效性效应。
