Data from: Demographic mechanisms of inbreeding adjustment through extra-pair reproduction

Abstract1. One hypothesis explaining extra-pair reproduction is that socially monogamous females mate with extra-pair males to adjust the coefficient of inbreeding (f) of extra-pair offspring (EPO) relative to that of within-pair offspring (WPO) they would produce with their socially paired male. Such adjustment of offspring f requires non-random extra-pair reproduction with respect to relatedness, which is in turn often assumed to require some mechanism of explicit pre-copulatory or post-copulatory kin discrimination. 2. We propose three demographic processes that could potentially cause mean f to differ between individual females' EPO and WPO given random extra-pair reproduction with available males without necessarily requiring explicit kin discrimination. Specifically, such a difference could arise if social pairings formed non-randomly with respect to relatedness or persisted non-randomly with respect to relatedness, or if the distribution of relatedness between females and their sets of potential mates changed during the period through which social pairings persisted. 3. We used comprehensive pedigree and pairing data from free-living song sparrows (Melospiza melodia) to quantify these three processes and hence investigate how individual females could adjust mean offspring f through instantaneously random extra-pair reproduction. 4. Female song sparrows tended to form social pairings with unrelated or distantly related males slightly less frequently than expected given random pairing within the defined set of available males. Furthermore, social pairings between more closely related mates tended to be more likely to persist across years than social pairings between less closely related mates. However, these effects were small and the mean relatedness between females and their sets of potential extra-pair males did not change substantially across the years through which social pairings persisted. 5. Our framework and analyses illustrate how demographic and social structuring within populations might allow females to adjust mean f of offspring through random extra-pair reproduction without necessarily requiring explicit kin discrimination, implying that adjustment of offspring f might be an inevitable consequence of extra-pair reproduction. New theoretical and empirical studies are required to explore the general magnitude of such effects and quantify the degree to which they could facilitate or constrain long-term evolution of extra-pair reproduction., Usage notesPairsData_DryadThis file contains data required for the basic descriptive analysis of social pairing in relation to kinship.NewMalesPairings_DryadThis file contains data required for the analysis of social pairing in relation to kinship between females and the 'new males' set of potential mates.AllMalesPairings_DryadThis file contains data required for the analysis of social pairing in relation to kinship between females and the 'all males' set of potential mates.PairPersistence_DryadThis file contains data required for the analysis of social pair persistence in relation to kinship.ChangeMeanK_DryadThis file contains data required for the analysis of changing mean kinship within the duration of females' social pairings.

摘要1. 解释婚外配繁殖的一项假说认为，社会一夫一妻制的雌性会与婚外雄性交配，以此调整婚外配后代（EPO）相对于其与配对雄性所生婚内后代（WPO）的近交系数（coefficient of inbreeding）。这类后代近交系数的调整需要基于亲缘关系的非随机婚外配繁殖，而这通常被认为需要明确的交配前或交配后亲属识别（kin discrimination）机制。2. 我们提出了三类人口统计过程：即便雌性与可获得雄性之间的婚外配繁殖为随机过程，也可导致不同雌性的婚外配后代与婚内后代的平均近交系数产生差异，且无需借助明确的亲属识别机制。具体而言，若社会配对的形成基于亲缘关系的非随机模式，或社会配对的存续与亲缘关系呈非随机关联，又或是雌性与其潜在配偶集合之间的亲缘关系分布在社会配对存续期内发生了变化，那么上述差异便可能出现。3. 我们利用野生歌带鹀（Melospiza melodia）的完整谱系（pedigree）与配对数据，对这三类过程进行量化，以此探究雌性个体如何通过瞬时随机的婚外配繁殖调整后代的平均近交系数。4. 歌带鹀雌性形成社会配对时，与无关或远缘雄性的配对频率，略低于在既定可用雄性集合内随机配对的预期水平。此外，配偶间亲缘关系越近，其社会配对跨年度存续的概率越高。不过这类效应较为微弱，且雌性与其潜在婚外配雄性集合之间的平均亲缘关系，在社会配对存续的年份中并未发生显著变化。5. 我们的研究框架与分析表明，种群内的人口统计与社会结构，可使雌性通过随机的婚外配繁殖调整后代的平均近交系数，且无需明确的亲属识别机制。这意味着后代近交系数的调整或许是婚外配繁殖的必然结果。未来需开展新的理论与实证研究，以探究这类效应的普遍强度，并量化其在多大程度上能够促进或制约婚外配繁殖的长期演化。使用说明- PairsData_Dryad：该文件包含开展亲缘关系相关社会配对基础描述性分析所需的数据。- NewMalesPairings_Dryad：该文件包含开展雌性与“潜在配偶新雄性集合”之间亲缘关系相关社会配对分析所需的数据。- AllMalesPairings_Dryad：该文件包含开展雌性与“全部潜在配偶雄性集合”之间亲缘关系相关社会配对分析所需的数据。- PairPersistence_Dryad：该文件包含开展亲缘关系相关社会配对存续性分析所需的数据。- ChangeMeanK_Dryad：该文件包含开展雌性社会配对存续期间平均亲缘关系变化分析所需的数据。