C-RUI:Behavior and the Major Histocompatibility Complex in Savannah Sparrows

0116139-弗里曼-加兰特1。科里·R·弗里曼-加兰特和纳撒尼尔·T·惠尔赖特，这是一份非专业的摘要，上面有提案的标题和你的全名。“近亲繁殖、雌性交配忠诚度和草原麻雀的主要组织相容性复合体”雌性麻雀经常在配对纽带之外交配，产生混合父子关系的幼鸟，在某些物种中，多达60%的幼鸟来自额外的配对受精。这种不忠行为的普遍存在对我们理解鸟类生物学具有重要意义。最近的研究将女性的婚姻忠诚度与男性父母照顾的生态和进化、社会交配系统、繁殖的分散和同步以及精心设计的性展示的形式和功能联系在一起。尽管多次交配很重要，但多次交配的适应意义仍然存在争议。虽然最近的几项研究支持这样的观点，即额外配对交配(EPC)允许雌性(通过提升父系的遗传质量)为其后代获得良好的基因，但许多其他研究发现，雌性交配的忠诚度与可能反映雄性质量的特征之间没有关系。事实上，雌性交配忠诚度的很大差异仍未得到解释，该领域几乎没有寻找到好基因假说的可行替代方案。好基因假说的一个推论提出，雌性确实使用EPC来提高幼崽的质量，但雌性选择的目标是母体和父系基因组之间的相互作用，而不是雄性本身的质量。这种个体优化或遗传兼容性假设现在已经在蛇、蜥蜴和伪蝎身上进行了探索，但在鸟类中很少有研究考虑到依赖于基因的交配偏好和最优的重要性。然而，对草原麻雀(Passerculus Sandwichensis)的初步研究强烈表明，雌性麻雀与主要组织相容性复合体(MHC)非随机(和错配)配对，MHC是一组负责引发脊椎动物适应性免疫反应的基因。此外，雌性与其社会伴侣的基因相似性预示着她的忠诚度：与相似雄性配对的雌性比与不同雄性配对的雌性更有可能产生额外的双胞胎。这些结果与在老鼠和人类身上进行的类似研究平行，并表明要么是遗传多样性的好处(在MHC)推动了雌性交配模式，要么是避免近亲繁殖是草原麻雀社会和遗传配偶选择的最终原因。有了NSF的资助，新的分子和分析技术将应用于之前野外工作中获得的样本。对萨凡纳麻雀的初步结果是基于1995年在加拿大新不伦瑞克肯特岛的38对麻雀筑巢得出的。为了确定雌性是否根据其MHC基因选择配对内和外配对，并纳入雌性配对忠诚度的其他潜在决定因素(如成年年龄、繁殖时机和表型质量)，这一分析将在1994年扩大。此外，将通过在2002年和2003年繁殖季节对麻雀的调查来评估总体遗传亲缘关系水平对雌性配对保真度、卵(胚胎)死亡率以及雏鸟和雏鸟存活率的重要性。近亲繁殖的成本和MHC杂合性的好处都表明，雌性麻雀应该避免遗传上相似的雄性受精。这项研究得益于先前开发的特定物种的MHC探针，以及对萨凡纳麻雀肯特岛种群近15年的野外和分子工作。这项研究将为在自由生活的鸣禽种群中MHC对社会和遗传交配模式的重要性提供首批测试之一。

0116139-Freeman-Gallant1. A lay abstract, with the title of the proposal and your full name at the top.Corey R. Freeman-Gallant and Nathaniel T. Wheelwright. "Inbreeding, Female Mating Fidelity, and theMajor Histocompatibility Complex in Savannah Sparrows"Female birds often copulate outside of the pair-bond to produce broods of mixed paternity, and in somespecies, as many as 60% of young derive from extra-pair fertilizations. The ubiquity of this infidelity hasimportant implications for our understanding of avian biology. Recent work has linked female matingfidelity to the ecology and evolution of male parental care, social mating systems, breeding dispersion andsynchrony, and the form and function of elaborate sexual displays. Despite its importance, the adaptivesignificance of multiple mating remains controversial. While several recent studies support the idea thatextra-pair copulations (EPCs) allow females to obtain good genes for their offspring (by trading-up) onthe genetic quality of sires), many others have found no relationship between female mating fidelity andtraits likely to reflect male quality. Indeed, much variation in female mating fidelity remains unexplained,and few feasible alternatives to the good genes hypothesis have been pursued in the field.A corollary to the good genes hypothesis proposes that females do use EPCs to increase the quality ofyoung, but it is the interaction between maternal and paternal genomes"and not male quality per se"thatis the target of female choice. This individual optimization or genetic compatibility hypothesis hasnow been explored in snakes, lizards, and pseudoscorpions, but few studies in birds have considered theimportance of genotype-dependent mating preferences and optima. Preliminary work with Savannahsparrows (Passerculus sandwichensis), however, strongly suggests that females pair nonrandomly (anddisassortatively) with respect to the major histocompatibility complex (Mhc), a group of genes responsiblefor eliciting the adaptive immune response of vertebrates. Moreover, a female's genetic similarity to hersocial mate predicts her fidelity: females paired to similar males are more likely to produce extra-pairyoung than females paired to dissimilar males. These results parallel similar studies in mice and humans,and suggest either that the benefits of genetic diversity (at the Mhc) drive female mating patterns or that theavoidance of inbreeding is an ultimate cause of social and genetic mate choice in Savannah sparrows.With NSF funding, new molecular and analytical techniques will applied to samples obtained duringprevious field work. Preliminary results with Savannah sparrows are based on 38 pairs nesting on KentIsland, New Brunswick, Canada in 1995. To determine whether females choose within- and extra-pairsires according to their Mhc genotype, and to incorporate other potential determinants of female matingfidelity (such as adult age, timing of breeding and phenotypic quality), the analysis will be extended topairs nesting in 1994. In addition, the importance of overall levels of genetic relatedness to female matingfidelity, the occurrence of egg (embryo) mortality, and the survivorship of nestlings and fledglings will beassessed by surveying sparrows during the 2002 and 2003 breeding seasons. Both the costs of inbreedingand the benefits of Mhc heterozygosity predict that females should avoid fertilizations from geneticallysimilar males.This research benefits from the prior development of a species-specific Mhc probe and nearly 15 yearsof field and molecular work on the Kent Island population of Savannah sparrows. This study will provideone of the first tests of the importance of the Mhc to social and genetic mating patterns in a free-livingpopulation of songbirds.