Johannesson Kerstin, Havenhand Jon N, Jonsson Per R, Lindegarth Mats, Sundin Annika, Hollander Johan
Department of Marine Ecology, Göteborg University, Tjärnö Marine Biological Laboratory, Strömstad, Sweden.
Evolution. 2008 Dec;62(12):3178-84. doi: 10.1111/j.1558-5646.2008.00510.x. Epub 2008 Sep 11.
Recent research has shown the potential for nonallopatric speciation, but we lack an adequate understanding of the mechanisms of prezygotic barriers and how these evolve in the presence of gene flow. The marine snail Littorina saxatilis has distinct ecotypes in different shore microhabitats. Ecotypes hybridize in contact zones, but gene flow is impeded by assortative mating. Earlier studies have shown that males and females of the same ecotype copulate for longer than mates of different ecotype. Here we report a new mechanism that further contributes to reproductive isolation between ecotypes in the presence of gene flow. This mechanism is linked to the ability of males to track potential partners by following their mucous trail. We show that cliff ecotype males follow the trails of females of the same ecotype for longer than females of the alternate (boulder) ecotype. In addition, cliff males are more likely to follow the mucous trail in the correct direction if the trail is laid by a cliff-female. The capacity to discriminate the ecotype of female mucous trails combined with differential copulation times creates a strong prezygotic reproductive barrier between ecotypes of L. saxatilis that reduces gene flow from cliff to boulder ecotypes by >/=80%.
最近的研究显示了非异域物种形成的可能性，但我们对合子前隔离机制以及这些机制在基因流动存在的情况下如何演化缺乏充分的了解。海蜗牛滨螺（Littorina saxatilis）在不同的海岸微生境中有不同的生态型。生态型在接触区杂交，但选型交配阻碍了基因流动。早期研究表明，相同生态型的雄性和雌性交配时间比不同生态型的配偶更长。在此，我们报告一种新机制，在基因流动存在的情况下，该机制进一步促进了生态型之间的生殖隔离。这种机制与雄性通过追踪潜在配偶的黏液痕迹来寻找它们的能力有关。我们发现，悬崖生态型的雄性追踪相同生态型雌性的痕迹的时间比追踪另一种（巨石）生态型雌性的痕迹的时间更长。此外，如果痕迹是由悬崖生态型的雌性留下的，悬崖生态型的雄性更有可能朝着正确的方向追踪黏液痕迹。辨别雌性黏液痕迹生态型的能力与不同的交配时间相结合，在滨螺的生态型之间形成了强大的合子前生殖屏障，使从悬崖生态型到巨石生态型的基因流动减少了≥80%。
