Wheatcroft David, Qvarnström Anna
Animal Ecology, Department of Ecology and Genetics, Uppsala University, Norbyvägen 18D, 752 36, Sweden.
Evolution. 2017 Jul;71(7):1776-1786. doi: 10.1111/evo.13267. Epub 2017 May 24.
Divergence of male sexual signals and female preferences for those signals often maintains reproductive boundaries between closely related, co-occurring species. However, contrasting sources of selection, such as interspecific competition, can lead to weak divergence or even convergence of sexual signals in sympatry. When signals converge, assortative mating can be maintained if the mating preferences of females diverge in sympatry (reproductive character displacement; RCD), but there are few explicit examples. Pied flycatchers (Ficedula hypoleuca) are sympatric with collared flycatchers (F. albicollis) on the Baltic island of Öland, where males from both species compete over nestboxes, their songs converge, and the two species occasionally hybridize. We compare song discrimination of male and female pied flycatchers on Öland and in an allopatric population on the Swedish mainland. Using field choice trials, we show that male pied flycatchers respond similarly to the songs of both species in sympatry and allopatry, while female pied flycatchers express stronger discrimination against heterospecific songs in sympatry than in allopatry. These results are consistent with RCD of song discrimination of female pied flycatchers where they co-occur with collared flycatchers, which should maintain species assortative mating despite convergence of male sexual signals.
雄性性信号与雌性对这些信号的偏好之间的差异通常会维持密切相关、同域分布物种之间的生殖界限。然而，不同的选择来源，如种间竞争，可能导致同域分布中性信号的差异减弱甚至趋同。当信号趋同时，如果雌性的交配偏好在同域分布中发生分化（生殖性状替代；RCD），则可以维持选型交配，但明确的例子很少。白斑姬鹟（Ficedula hypoleuca）与白领姬鹟（F. albicollis）在波罗的海的厄兰岛上同域分布，在那里两种雄性会争夺巢箱，它们的歌声趋同，且这两个物种偶尔会杂交。我们比较了厄兰岛以及瑞典大陆一个异域分布种群中白斑姬鹟雌雄个体对歌声的辨别能力。通过野外选择试验，我们发现，在同域分布和异域分布中，白斑姬鹟雄性对两种物种的歌声反应相似，而白斑姬鹟雌性在同域分布中对异种歌声的辨别能力比在异域分布中更强。这些结果与白斑姬鹟与白领姬鹟同域分布时歌声辨别能力的生殖性状替代一致，这应该会在雄性性信号趋同的情况下维持物种选型交配。
