Data from: The inbreeding strategy of a solitary primate, Microcebus murinus

Inbreeding depression may be common in nature, reflecting either the failure of inbreeding avoidance strategies or inbreeding tolerance when avoidance is costly. The combined assessment of inbreeding risk, avoidance and depression is therefore fundamental to evaluate the inbreeding strategy of a population, that is how individuals respond to the risk of inbreeding. Here, we use the demographic and genetic monitoring of 10 generations of wild grey mouse lemurs (Microcebus murinus), small primates from Madagascar with overlapping generations, to examine their inbreeding strategy. Grey mouse lemurs have retained ancestral mammalian traits, including solitary lifestyle, polygynandry and male-biased dispersal, and may therefore offer a representative example of the inbreeding strategy of solitary mammals. The occurrence of close kin among candidate mates was frequent in young females (~37%, most often the father) and uncommon in young males (~6%) due to male-biased dispersal. However, close kin consistently represented a tiny fraction of candidate mates (< 1%) across age and sex categories. Mating biases favouring partners with intermediate relatedness were detectable in yearling females and adult males, possibly partly caused by avoidance of daughter–father matings. Finally, inbreeding depression, assessed as the effect of heterozygosity on survival, was undetectable using a capture–mark–recapture study. Overall, these results indicate that sex-biased dispersal is a primary inbreeding avoidance mechanism at the population level, and mating biases represent an additional strategy that may mitigate residual inbreeding costs at the individual level. Combined, these mechanisms explain the rarity of inbreeding and the lack of detectable inbreeding depression in this large, genetically diverse population.

近交衰退（inbreeding depression）在自然界中或较为普遍，其成因要么是近交规避（inbreeding avoidance）策略失效，要么是当规避近交存在成本时，物种选择了近交耐受。因此，对近交风险、近交规避与近交衰退进行综合评估，是解析种群近交策略（即个体如何应对近交风险）的核心所在。本研究借助对10个世代的野生灰鼠狐猴（Microcebus murinus）——这种原产于马达加斯加的世代重叠型小型灵长类动物——的种群统计与遗传监测数据，对其近交策略展开探究。灰鼠狐猴保留了哺乳动物祖先的典型特征，包括独居习性、混交制（polygynandry）以及雄性偏向扩散，因此可作为独居哺乳动物近交策略的代表性研究案例。由于雄性偏向扩散的特性，候选配偶中存在近缘亲属的情况在年轻雌性中较为常见（约37%，最常见的近缘亲属为其父本），而在年轻雄性中则较为少见（约6%）。但在所有年龄与性别类群中，近缘亲属在候选配偶中的占比始终极低（不足1%）。在一岁龄雌性与成年雄性中，可观测到对亲缘关系中等程度配偶的交配偏好，这一现象可能部分源于对父女交配的规避。最后，本研究通过标记重捕法（capture–mark–recapture）评估杂合度对存活的影响以衡量近交衰退，却未检测到显著的近交衰退信号。综合来看，本研究结果表明：雄性偏向扩散是种群层面近交规避的核心机制，而交配偏好则是另一项补充策略，可在个体层面缓解残余的近交繁殖成本。上述两种机制共同作用，解释了该大型遗传多样性种群中近交事件罕见且未检测到显著近交衰退的原因。