Fossøy Frode, Johnsen Arild, Lifjeld Jan T
Natural History Museum, University of Oslo, Blindern, NO-0318, Oslo, Norway.
Evolution. 2008 Jan;62(1):145-56. doi: 10.1111/j.1558-5646.2007.00284.x. Epub 2007 Dec 5.
The adaptive function of female extrapair mating in socially monogamous passerines is currently debated. In the bluethroat (Luscinia s. svecica), a previous study showed that offspring sired by extrapair males had a higher cell-mediated immunity than their within-pair half siblings, suggesting an immunogenetic benefit of extrapair mating in this species. Here, we expanded that dataset with two more years and investigated the association between extrapair paternity and microsatellite multilocus heterozygosity, in addition to cell-mediated immunity. We found that extrapair offspring were more heterozygous than their within-pair half siblings, and corroborated the previous finding of enhanced cellular immunity in extrapair offspring in this four-year dataset. The increased heterozygosity among extrapair offspring appeared to be a result of extrapair mates being less genetically similar than pair mates, and also less genetically similar than expected by random choice. Together with previous findings in this species, showing that the majority of females participate in extrapair copulations, our results indicate a postcopulatory cryptic female choice of genetically dissimilar males. The enhanced cellular immunity and increased heterozygosity were not related to each other, and hence our results indicate two independent genetic benefits of extrapair mating in the bluethroat.
雌性配偶外交配在社会性一夫一妻制雀形目鸟类中的适应性功能目前存在争议。在蓝喉歌鸲（Luscinia s. svecica）中，先前的一项研究表明，配偶外交配雄性所生的后代比其配偶内的同父异母或同母异父兄弟姐妹具有更高的细胞介导免疫力，这表明该物种中配偶外交配具有免疫遗传学益处。在此，我们将该数据集扩展了两年，并除了研究细胞介导免疫力外，还调查了配偶外交配亲子关系与微卫星多位点杂合性之间的关联。我们发现，配偶外交配的后代比其配偶内的同父异母或同母异父兄弟姐妹更具杂合性，并在这个四年的数据集中证实了先前关于配偶外交配后代细胞免疫力增强的发现。配偶外交配后代杂合性增加似乎是由于配偶外交配的配偶在基因上比配偶内的配偶相似度更低，而且也比随机选择预期的相似度更低。结合该物种先前的研究结果，表明大多数雌性参与配偶外交配，我们的结果表明交配后雌性对基因不相似雄性的隐秘选择。细胞免疫力增强和杂合性增加彼此无关，因此我们的结果表明蓝喉歌鸲配偶外交配具有两种独立的遗传益处。
