Foerster K, Valcu M, Johnsen A, Kempenaers B
Max Planck Institute for Ornithology, Department of Behavioural Ecology & Evolutionary Genetics, PO Box 1564, D-82305 Starnberg/Seewiesen, Germany.
Mol Ecol. 2006 Dec;15(14):4555-67. doi: 10.1111/j.1365-294X.2006.03091.x.
Inbreeding depression, as commonly found in natural populations, should favour the evolution of inbreeding avoidance mechanisms. If natal dispersal, the first and probably most effective mechanism, does not lead to a complete separation of males and females from a common origin, a small-scale genetic population structure may result and other mechanisms to avoid inbreeding may exist. We studied the genetic population structure and individual mating patterns in blue tits (Parus caeruleus). The population showed a local genetic structure in two out of four years: genetic relatedness between individuals (estimated from microsatellite markers) decreased with distance. This pattern was mainly caused by immigrants to the study area; these, if paired with fellow immigrants, were more related than expected by chance. Since blue tits did not avoid inbreeding with their social partner, we examined if individuals preferred less related partners at later stages of the mate choice process. We found no evidence that females or males avoided inbreeding through extra-pair copulations or through mate desertion and postbreeding dispersal. Although the small-scale genetic population structure suggests that blue tits could use a simple rule of thumb to select less related mates, females did not generally prefer more distantly breeding extra-pair partners. However, the proportion of young fathered by an extra-pair male in mixed paternity broods depended on the genetic relatedness with the female. This suggests that there is a fertilization bias towards less related copulation partners and that blue tits are able to reduce the costs of inbreeding through a postcopulatory process.
近亲繁殖衰退在自然种群中普遍存在，这应该会促进近亲繁殖避免机制的进化。如果出生扩散（这是第一种且可能是最有效的机制）不能导致来自共同起源的雄性和雌性完全分离，可能会产生小规模的遗传种群结构，并且可能存在其他避免近亲繁殖的机制。我们研究了蓝山雀（Parus caeruleus）的遗传种群结构和个体交配模式。该种群在四年中的两年呈现出局部遗传结构：个体之间的遗传相关性（根据微卫星标记估计）随距离增加而降低。这种模式主要是由迁入研究区域的个体导致的；这些个体如果与其他迁入个体配对，其亲缘关系比随机预期的更为密切。由于蓝山雀不会避免与其社会伴侣进行近亲繁殖，我们研究了个体在配偶选择过程的后期是否更倾向于选择亲缘关系较远的伴侣。我们没有发现雌性或雄性通过杂交或通过抛弃配偶及繁殖后扩散来避免近亲繁殖的证据。尽管小规模的遗传种群结构表明蓝山雀可以使用一个简单的经验法则来选择亲缘关系较远的配偶，但雌性通常并不更倾向于选择繁殖地距离更远的杂交伴侣。然而，在混合父权育雏中，杂交雄性所育幼鸟的比例取决于与雌性的遗传相关性。这表明对于亲缘关系较远的交配伴侣存在受精偏好，并且蓝山雀能够通过交配后的过程降低近亲繁殖的成本。
