Data from: Additive genetic variance in polyandry enables its evolution, but polyandry is unlikely to evolve through sexy or good sperm processes

Polyandry is widespread despite its costs. The sexually selected sperm hypotheses (‘sexy’ and ‘good’ sperm) posit that sperm competition plays a role in the evolution of polyandry. Two poorly studied assumptions of these hypotheses are the presence of additive genetic variance in polyandry and sperm competitiveness. Using a quantitative genetic breeding design in a natural population of Drosophila melanogaster, we first established the potential for polyandry to respond to selection. We then investigated whether polyandry can evolve through sexually selected sperm processes. We measured lifetime polyandry and offensive sperm competitiveness (P2) while controlling for sampling variance due to male x male x female interactions. We also measured additive genetic variance in egg-to-adult viability and controlled for its effect on P2 estimates. Female lifetime polyandry showed significant and substantial additive genetic variance and evolvability. In contrast, we found little genetic variance or evolvability in P2 or egg-to-adult viability. Additive genetic variance in polyandry highlights its potential to respond to selection. However, the low levels of genetic variance in sperm competitiveness suggest the evolution of polyandry may not be driven by sexy sperm or good sperm processes.

尽管伴随诸多适应成本，一妻多夫制（polyandry）仍广泛存在于自然界中。性选择精子假说（涵盖“性感精子”与“优质精子”两种亚型）提出，精子竞争在一妻多夫制的演化进程中发挥了关键作用。该类假说存在两个尚未得到充分研究的前提假设：即一妻多夫制与精子竞争力均存在加性遗传方差（additive genetic variance）。本研究以自然种群中的黑腹果蝇（Drosophila melanogaster）为实验材料，采用数量遗传学育种设计，首先验证了一妻多夫制对选择作用的响应潜力，随后探究了一妻多夫制是否可通过性选择精子相关过程发生演化。我们测定了雌性终身多配行为与进攻型精子竞争力（P2），同时控制了雄-雄-雌互作带来的抽样方差；此外还测定了卵到成虫存活率（egg-to-adult viability）的加性遗传方差，并校正了该方差对P2测定值的影响。结果显示，雌性终身多配行为表现出显著且可观的加性遗传方差与演化潜力。与之相反，我们在P2与卵到成虫存活率中仅检测到极少量的遗传方差与演化潜力。一妻多夫制的加性遗传方差表明其具备对选择作用做出响应的演化潜力，但精子竞争力的遗传方差水平较低，这意味着一妻多夫制的演化可能并非由性感精子或优质精子过程所驱动。