Coevolution of Male and Female Genital Morphology in Waterfowl
Coevolution of Male and Female Genital Morphology in Waterfowl
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DOI：
10.1371/journal.pone.0000418
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发表时间：
2007-05-02
期刊：
影响因子：
3.7
通讯作者：
Birkhead, Tim R.
中科院分区：
文献类型：
--
作者：
Brennan, Patricia L. R.;Prum, Richard O.;Birkhead, Tim R.
大多数鸟类只有简单的生殖器；雄性没有外生殖器，雌性只有简单的阴道。然而，雄性水禽有一个，其长度(1.5-40厘米)和形态特征因物种而异，并与水禽物种之间强迫配对交配的频率呈正相关。在这里，我们报道了水禽雌性生殖器形态的复杂性，并描述了在鸟类中史无前例的阴道形态变异。这种变异包括两个解剖学上的新奇之处：(I)死端囊和(Ii)顺时针线圈。这些阴道结构的功能似乎是在没有女性合作的情况下排除逆时针螺旋的男性的插入。对16种水禽的系统发育比较分析表明，阴道精加工程度与长度呈正相关，表明雌性的形态复杂性与雄性的长度是共同进化的。两性选择很可能是所观察到的共同进化的原因，尽管很难确定具体的机制。我们的结果表明，雌性已经进化出了一种神秘的解剖选择机制，以应对被迫的额外配对交配。
Most birds have simple genitalia; males lack external genitalia and females have simple vaginas. However, male waterfowl have a phallus whose length (1.5->40 cm) and morphological elaborations vary among species and are positively correlated with the frequency of forced extra-pair copulations among waterfowl species. Here we report morphological complexity in female genital morphology in waterfowl and describe variation vaginal morphology that is unprecedented in birds. This variation comprises two anatomical novelties: (i) dead end sacs, and (ii) clockwise coils. These vaginal structures appear to function to exclude the intromission of the counter-clockwise spiralling male phallus without female cooperation. A phylogenetically controlled comparative analysis of 16 waterfowl species shows that the degree of vaginal elaboration is positively correlated with phallus length, demonstrating that female morphological complexity has co-evolved with male phallus length. Intersexual selection is most likely responsible for the observed coevolution, although identifying the specific mechanism is difficult. Our results suggest that females have evolved a cryptic anatomical mechanism of choice in response to forced extra-pair copulations.