Choosing mates wisely Hybridization between species has long been seen as an accidental contributor to evolution in some cases and as a dead end in others. New evidence is emerging, however, that hybridization may have played important, and nonrandom, roles in adaptation. Chen and Pfennig describe just such a case where female Plains spadefoot toads preferentially choose males from another toad species, the Mexican spadefoot, as mates, but only under certain environmental conditions (see the Perspective by Zuk). The offspring of this preferred hybrid mating event have higher fitness than nonhybrids in the same environment. Thus, not only do hybrids have an advantage, but females of one species are exerting a selective influence on the other species. Science, this issue p. 1377; see also p. 1304 Female spadefoot toads choose mates of a different species to increase their offspring’s fitness. Hybridization—interbreeding between species—is generally thought to occur randomly between members of two species. Contrary to expectation, female plains spadefoot toads (Spea bombifrons) can increase their evolutionary fitness by preferentially mating with high-quality males of another species, the Mexican spadefoot toad (Spea multiplicata). Aspects of Mexican spadefoot males’ mating calls predict their hybrid offspring’s fitness, and plains spadefoot females prefer Mexican spadefoot males on the basis of these attributes, but only in populations and ecological conditions where hybridization is adaptive. By selecting fitness-enhancing mates of another species, females increase hybridization’s benefits and exert sexual selection across species. Nonrandom mating between species can thereby increase the potential for adaptive gene flow between species so that adaptive introgression is not simply happenstance.

中文翻译：

---

从事适应性杂交的雌性蟾蜍更喜欢高质量的异种作为配偶

明智地选择配偶长期以来，物种之间的杂交在某些情况下被视为进化的偶然因素，而在其他情况下则被视为死胡同。然而，新的证据表明，杂交可能在适应中发挥了重要的、非随机的作用。Chen 和 Pfennig 描述了这样一种情况，雌性平原黑鲀优先选择另一种蟾蜍墨西哥黑鲀中的雄性作为配偶，但仅限于某些环境条件下（见 Zuk 的观点）。在相同环境中，这种首选的杂交交配事件的后代比非杂交后代具有更高的适应性。因此，杂交种不仅具有优势，而且一个物种的雌性正在对另一个物种施加选择性影响。科学，这个问题 p。第1377章 另见第 1304 雌性铲足蟾蜍选择不同物种的配偶来增加后代的健康。杂交——物种间的杂交——通常被认为随机发生在两个物种的成员之间。与预期相反，雌性平原铲足蟾蜍 (Spea bombifrons) 可以通过优先与另一物种墨西哥铲足蟾蜍 (Spea multiplicata) 的优质雄性交配来增加其进化适应性。墨西哥铲足雄性的交配叫声预测了它们杂交后代的健康状况，平原铲足雌性基于这些属性更喜欢墨西哥铲足雄性，但仅限于杂交具有适应性的种群和生态条件。通过选择另一个物种的增强健康的配偶，雌性增加了杂交的好处并在物种之间进行性选择。