社会性单配制鸟类婚外父权的发生和影响因素

The Occurrence and Factors of the Extra-pair Paternity in Socially Monogamous Birds

一雌一雄单配制鸟类中,雌性个体与配偶外雄性发生交配的行为称为婚外交配,继而导致了婚外受精产生婚外子代的现象称为产生了婚外父权。婚外父权广泛存在于鸟类中,针对其发生和影响因素已经成为了鸟类行为生态学研究的热点。本文收集了近十年社会性单配制鸟类婚外父权方面的研究文献,从婚外父权的发生及其影响因素两个方面综述了单配制鸟类婚外父权的研究进展。婚外父权发生原因的探讨主要包括:1、从两性的角度探讨雌雄两性在婚外行为中不同的进化繁殖策略。雄性策略旨在增加自身的繁殖输出;有关雌性策略则提出了确保受精假说、食物供给假说、遗传利益假说等,但目前尚存争议;2、在遗传利益假说中较常见的又分为3个假说:"优秀基因"假说、"遗传相容性"假说和"遗传多样性"假说,该三种假说是针对雌性从遗传方面获得的利益而提出的,不断有报道指出雌性配偶选择会被潜在的雄性遗传特性所影响;3、非遗传利益——母系效应影响婚外父权的进化。一些研究指出遗传质量参数,如体重、身体大小、存活率和免疫应答等方面可能会存在母系效应。婚外父权发生的影响因素这里主要指环境因素,包括繁殖同步性、繁殖密度、栖息地环境、产卵及孵化时机等。由于物种不同,受到环境压力不同,导致婚外父权发生率千差万别。最后本文针对未来的研究方向做出了展望。尽管近十年的研究进一步解释了鸟类婚外父权现象,但是该领域仍然存在并且产生了许多新的未解决的问题,而相关实验操作和理论的完善是深入探讨这些问题的关键。

Researchers have found that extra-pair paternity prevails among socially monogamous birds and this phenomenon challenges traditional views of mating system by using molecular technology. Contrary to prior expectations, birds are very rarely sexual monogamous since extra-pair offspring has been found in approximately 90% of species. Even among socially monogamous species,over 11% of offspring are extra-pair paternity on average. Extra-pair paternity arises when female birds engage in extra-pair copulations with males other than their social mates,frequently resulting in broods with multiple paternity which contain offspring sired by the social male and offspring sired by extra-pair males. A large and solid body of evidence has impressivelydemonstrated that extra-pair paternity is the rule rather than the exception in birds（ especially in passerines）,and a number of synthetic contributions have reviewed this field with its various ramifications over the last decade. Extra-pair paternity is widespread in avian species so that the reason for the occurrence of extra-pair paternity and the influence has become the focus researches in the behavioral ecology of avian species. Based on the researches about avian extra-pair paternity over the past decade,this paper reviews the research progress and summarizes two major aspects on causes and effects of extra-pair paternity. Investigating the causes of extramarital paternity includes： 1,we explore the different sexes in the evolution of reproductive strategies from gender perspective. Male reproductive strategies are designed to increase their output; female strategies are proposed to ensure that female fertility hypothesis,the food supply hypothesis,the hypothesis of genetic benefits,etc.,but still controversial. 2,the genetic benefit hypothesis（ ＂good genes＂hypothesis,＂genetic compatibility＂hypothesis,the hypothesis of genetic diversity） proposes that extra-pair sires provide alleles of superior quality and / or better compatibility compared to the social mate,resulting in offspring of higher reproductive value. One frequently adopted approach to test this idea is to compare the performance of maternal half-siblings in broods with multiple paternities. However,results did not come to a conclusion,some studies failed to reveal any systematic differences in maternal half-sibling performance,even in the same or in closely related species. Furthermore,application of identical experimental protocols（ e. g. the phytohemagglutinin test of cellular immunocompetence） in different species with similar extra-pair mating systems produced mixed results. The inconsistencies of results across extra-pair paternity studies may be caused by methodological challenges and / or reflect true and meaningful differences in the respective study systems. 3,non-genetic benefit-maternal effects influence the evolution of extrapair paternity. Some studies indicated that genetic quality,such as weight,body size,survival and immune responses,etc may be effected by maternal effects.We also summarize environmental factors affecting the occurrence of extra-pair paternity include reproductive synchrony,breeding density,habitat,etc. Different species have different environmental pressures resulting in the difference of extra-pair paternity rate. Finally,we make prospects for the future research. Despite nearly a decade of researches to further explain the phenomenon of extra-pair paternity in birds,a certain reason is still unknown. Experimental operation and the improvement of the theory are keys to reach a more comprehensive solution for these problems.