Data from: No selection for change in polyandry under experimental evolution

What drives mating system variation is a major question in evolutionary
biology. Female multiple mating (polyandry) has diverse evolutionary
consequences, and there are many potential benefits and costs of
polyandry. However, our understanding of its evolution is biased towards
studies enforcing monandry in polyandrous species. What drives and
maintains variation in polyandry between individuals, genotypes,
populations and species remains poorly understood. Genetic variation in
polyandry may be actively maintained by selection, or arise by chance if
polyandry is selectively neutral. In Drosophila pseudoobscura, there is
genetic variation in polyandry between and within populations. We used
isofemale lines to found replicate populations with high or low initial
levels of polyandry, and tracked polyandry under experimental evolution
over seven generations. Polyandry remained relatively stable, reflecting
the starting frequencies of the experimental populations. There were no
clear fitness differences between high versus low polyandry genotypes, and
there was no signature of balancing selection. We confirmed these patterns
in direct comparisons between evolved and ancestral females, and found no
consequences of polyandry for female fecundity. The absence of
differential selection even when initiating populations with major
differences in polyandry casts some doubt on the importance of polyandry
for female fitness.

什么驱动交配系统变异是进化生物学中的核心问题。雌性多重交配（polyandry）具有多样的进化后果，且多配制存在诸多潜在利弊。然而，我们对其进化的理解受限于在多配制物种中强制实施单配制的研究。驱动并维持个体、基因型、种群及物种间多配制变异的因素仍知之甚少。多配制的遗传变异可能通过选择被主动维持，或若多配制为选择中性则随机产生。在拟暗果蝇（Drosophila pseudoobscura）中，种群间及种群内的多配制存在遗传变异。我们利用单雌系建立了初始多配制水平高低不同的重复种群，并在实验进化条件下追踪了七代的多配制变化。多配制保持相对稳定，反映了实验种群的初始频率。高与低多配制基因型之间无明显适合度差异，且未发现平衡选择的信号。通过直接比较进化后与祖先雌性个体，我们证实了这些模式，并发现多配制对雌性繁殖力无显著影响。即使在初始多配制存在显著差异的种群中也未观察到分化选择，这对多配制对雌性适合度的重要性提出了一定质疑。