Data from: Evolution of inbreeding avoidance and inbreeding preference through mate choice among interacting relatives

While extensive population genetic theory predicts conditions favoring evolution of self-fertilization versus outcrossing, there is no analogous theory that predicts conditions favoring evolution of inbreeding avoidance or inbreeding preference enacted through mate choice given obligate biparental reproduction. Multiple interacting processes complicate the dynamics of alleles underlying such inbreeding strategies, including sexual conflict, distributions of kinship, genetic drift, purging of mutation load, direct costs, and restricted kin discrimination. We incorporated these processes into an individual-based model to predict conditions where selection should increase or decrease frequencies of alleles causing inbreeding avoidance or inbreeding preference when females or males controlled mating. Selection for inbreeding avoidance occurred given strong inbreeding depression when either sex chose mates, while selection for inbreeding preference occurred given very weak inbreeding depression when females chose but never occurred when males chose. Selection for both strategies was constrained by direct costs and restricted kin discrimination. Purging was negligible, but allele frequencies were strongly affected by drift in small populations, while selection for inbreeding avoidance was weak in larger populations because inbreeding risk decreased. Therefore, while selection sometimes favored alleles underlying inbreeding avoidance or preference, evolution of such strategies may be much more restricted and stochastic than is commonly presumed.尽管现有成熟的种群遗传学理论已可预测利于自交（self-fertilization）相较于异交（outcrossing）演化的条件，但目前尚无类似理论能够预测：在专性双亲繁殖（obligate biparental reproduction）的前提下，通过配偶选择实现近交回避（inbreeding avoidance）或近交偏好（inbreeding preference）的演化所需的有利条件。 多种相互作用的过程会使这类近交策略背后的等位基因（allele）动力学变得复杂，其中包括性冲突（sexual conflict）、亲缘关系分布、遗传漂变（genetic drift）、突变负荷清除（purging of mutation load）、直接成本以及有限的亲缘识别（kin discrimination）能力。 我们将上述过程整合进一个基于个体的模型（individual-based model）中，以此预测：当雌性或雄性主导配偶选择时，自然选择会如何增加或降低引发近交回避或近交偏好的等位基因的频率。 当任一性别主导配偶选择且存在强烈近交衰退（inbreeding depression）时，自然选择会青睐近交回避策略；而当雌性主导配偶选择且近交衰退极微弱时，自然选择会青睐近交偏好策略，但若由雄性主导配偶选择，则永远不会出现对近交偏好的选择。 两种策略所受的自然选择均会受到直接成本与有限亲缘识别能力的制约。 突变负荷清除的作用可忽略不计，但小种群中的等位基因频率会受到遗传漂变的强烈影响；而在大种群中，由于近交风险降低，对近交回避的选择作用会相对较弱。 因此，尽管自然选择有时会青睐与近交回避或近交偏好相关的等位基因，但这类策略的演化过程可能比通常所认为的更为受限且更具随机性。