Evolutionary biology of enantiomorphy and mirror-image populations in tree snails.

我们已经成功地拍摄了一部记录交配行为的电影，这可能解释了树蜗牛物种内的对映。目前认为，对映体不能以面对面交配的方式实现手性交配，即两对手性对映体同时进行对等交配。令人惊讶的是，通过野外观察和实验室实验观察，我们发现了一种手性二态物种atricallsus以这种方式交配。视频-电影分析证实了它们在面对面的位置上进行了双向交配。根据我们对基于照片和视频图像的视觉信息的分析，很明显，具有左右颠倒生殖器的对映体可以进行的相互插入，这在物理上是几乎不可能的。因此，目前的结果暴露了一个新的问题：它们如何同时实现对映体之间的互换交配。我们没有检测到它们的行为有任何独特之处，表现出典型的面对面交配。相反，视觉记录表明它们可能有生殖器和插入行为，使它们能够通过克服物理限制相互交配。分子系统发育分析的结果表明，手性二型性物种群是单系进化的。在该群体的祖先最初从右旋物种分化时，对映体已经演变为在两性属整个辐射过程中一直保持的祖先状态。这种手性差异的模式表明，种群内的对映同构可以通过进化获得特定的特征来维持。

We have succeeded in film recording a mating behavior that may explain how the enantiomorphy within species of tree snails Amphidromus. It is currently believed that the enantiomorphs could not achieve inter-chiral mating in the mode of face-to-face mating in which the two partners perform reciprocal matings simultaneously. Surprisingly we have discovered that one of chirally dimorphic species Amphidromus atricallosus copulates in this mode by means of field observations and experimental observations in the laboratory. The video-film analysis has confirmed their two-way copulation in the face-to-face position.According to our analysis of visual information based on photographs and video images, it is clear that the enantiomorphs with left-right reversed genitalia can perform reciprocal insertion of penes which are supposed to be physically hardly possible. Therefore, the current results have exposed a new question ; how do they achieve the reciprocal copulation between the enantiomorphs simultaneously. We have not detected any uniqueness in their behavior that exhibit a typical face-to-face mating. Instead, the visual record suggests that they may have genitalia and insertion behavior that allows them to copulate each other by overcoming the physical constraint.The results of molecular phylogenetic analysis have demonstrated that the chirally dimorphic group of species is monophyletic. At the initial divergence of the ancestor of the group from a dextral species, the enantiomorphy has evolved as the ancestral state maintained throughout the radiation of the genus Amphidromus. This pattern of chiral divergence suggests that the enantiomorphy within populations could be maintained by evolutionary acquisition of a particular character.