Veen T, Borge T, Griffith S C, Saetre G P, Bures S, Gustafsson L, Sheldon B C
Department of Animal Ecology, Evolutionary Biology Centre, Uppsala University, SE-752 36 Uppsala, Sweden.
Nature. 2001 May 3;411(6833):45-50. doi: 10.1038/35075000.
Hybridization in natural populations is strongly selected against when hybrid offspring have reduced fitness. Here we show that, paradoxically, pairing with another species may offer the best fitness return for an individual, despite reduced fitness of hybrid offspring. Two mechanisms reduce the costs to female collared flycatchers of pairing with male pied flycatchers. A large proportion of young are sired by conspecific male collared flycatchers through extra-pair copulations, and there is a bias in favour of male offspring (which, unlike females, are fertile) within hybrid pairs. In combination with temporal variation in breeding success, these cost-reducing mechanisms yield quantitative predictions about when female collared flycatchers should accept a male pied flycatcher as a mate; empirical data agree with these predictions. Apparent hybridization may thus represent adaptive mate choice under some circumstances.
当杂交后代的适应性降低时，自然种群中的杂交会受到强烈的选择抑制。然而，我们在此表明，矛盾的是，尽管杂交后代的适应性降低，但与另一个物种配对可能为个体带来最佳的适应性回报。有两种机制降低了雌性白领姬鹟与雄性斑姬鹟配对的成本。很大一部分幼鸟是由同种雄性白领姬鹟通过婚外交配所生，并且在杂交配对中存在对雄性后代（与雌性不同，雄性可育）的偏好。结合繁殖成功率的时间变化，这些成本降低机制对雌性白领姬鹟何时应接受雄性斑姬鹟作为配偶产生了定量预测；实证数据与这些预测相符。因此，在某些情况下，明显的杂交可能代表了适应性配偶选择。
