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

0116139 -弗里曼gallant1。一份通俗的摘要，上面有提案的标题和你的全名。科里·r·弗里曼-加兰特和纳撒尼尔·t·惠尔赖特。《近亲繁殖、雌性交配忠诚和萨凡纳麻雀的主要组织相容性复合体》雌鸟经常在配偶关系之外交配，以产生混合父系的后代，在某些物种中，多达60%的后代来自额外的配偶受精。这种不忠现象的普遍存在对我们理解鸟类生物学具有重要意义。最近的研究将雌性的交配忠诚与雄性亲代抚育的生态和进化、社会交配系统、繁殖分散和同步，以及精心制作的性展示的形式和功能联系起来。尽管多重交配很重要，但其适应性意义仍然存在争议。虽然最近的一些研究支持这样的观点，即额外配对交配（EPCs）允许女性（通过交换）后代的遗传质量来为后代获得良好的基因，但其他许多研究发现，女性的交配忠诚度与可能反映男性质量的特征之间没有关系。事实上，女性交配忠诚度的许多变化仍然无法解释，并且在该领域中几乎没有可行的替代方案来追求好基因假说。良好基因假说的一个推论是，女性确实使用EPCs来提高后代的质量，但女性选择的目标是母亲和父亲基因组之间的相互作用，“而不是男性质量本身”。这种个体优化或遗传相容性假说已经在蛇、蜥蜴和假蝎子中得到了探索，但在鸟类中很少有研究考虑到基因型依赖的交配偏好和优化的重要性。然而，对Savannahsparrows （Passerculus sandwich sis）的初步研究强烈表明，雌性在主要组织相容性复合体（Mhc）方面是非随机（和非分类）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：与相似的雄性配对的雌性比与不相似的雄性配对的雌性更有可能产生额外的后代。这些结果与在小鼠和人类身上进行的类似研究相似，表明要么是遗传多样性（在Mhc上）的好处驱动了雌性交配模式，要么是避免近亲繁殖是萨凡纳麻雀社会和遗传配偶选择的最终原因。在NSF的资助下，新的分子和分析技术将应用于以前野外工作中获得的样品。萨凡纳麻雀的初步结果是基于1995年在加拿大新不伦瑞克的肯斯兰筑巢的38对麻雀。为了确定雌性是否根据其Mhc基因型选择内对和外对，并纳入雌性交配保真度的其他潜在决定因素（如成年年龄、繁殖时间和表型质量），该分析将扩展到1994年的鸟类筑巢。此外，在2002年和2003年的繁殖季节，将通过调查麻雀来评估遗传亲缘关系总体水平对雌性交配保真度、蛋（胚胎）死亡率的发生以及雏鸟和雏鸟的存活率的重要性。近交的代价和Mhc杂合性的好处都预示着雌性应该避免与基因相似的雄性受精。这项研究得益于先前开发的一种物种特异性Mhc探针和近15年对肯特岛萨凡纳麻雀种群的野外和分子工作。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.