Department of Genetics, Evolution and Environment, University College London, Gower Street, London, WC1E 6BT, UK.
CoMPLEX, University College London, Gower Street, London, WC1E 6BT, UK.
Heredity (Edinb). 2019 Jun;122(6):916-926. doi: 10.1038/s41437-018-0166-y. Epub 2018 Nov 22.
Meiotic drive genes cause the degeneration of non-carrier sperm to bias transmission in their favour. Males carrying meiotic drive are expected to suffer reduced fertility due to the loss of sperm and associated harmful side-effects of the mechanisms causing segregation distortion. However, sexual selection should promote adaptive compensation to overcome these deleterious effects. We investigate this using SR, an X-linked meiotic drive system in the stalk-eyed fly, Teleopsis dalmanni. Despite sperm destruction caused by drive, we find no evidence that SR males transfer fewer sperm to the female's spermathecae (long-term storage organs). Likewise, migration from the spermathecae to the ventral receptacle for fertilisation is similar for SR and wildtype male sperm, both over short and long time-frames. In addition, sperm number in storage is similar even after males have mated multiple times. Our study challenges conventional assumptions about the deleterious effects of drive on male fertility. This suggests that SR male ejaculate investment per ejaculate has been adjusted to match sperm delivery by wildtype males. We interpret these results in the light of recent theoretical models that predict how ejaculate strategies evolve when males vary in the resources allocated to reproduction or in sperm fertility. Adaptive compensation is likely in species where meiotic drive has persisted over many generations and predicts a higher stable frequency of drive maintained in wild populations. Future research must determine exactly how drive males compensate for failed spermatogenesis, and how such compensation may trade-off with investment in other fitness traits.
减数分裂驱动基因导致非携带者精子的退化，从而有利于它们的传递。携带减数分裂驱动的雄性由于精子的损失以及导致分离扭曲的机制的相关有害副作用，预计会降低生育能力。然而，性选择应该促进适应性补偿，以克服这些有害影响。我们使用 Teleopsis dalmanni 中的 X 连锁减数分裂驱动系统 SR 来研究这一点。尽管驱动导致精子破坏，但我们没有发现证据表明 SR 雄性向雌性的受精管（长期储存器官）输送的精子较少。同样，对于 SR 和野生型雄性精子，从受精管向腹接收器的迁移在短时间和长时间内都是相似的。此外，即使雄性已经多次交配，储存的精子数量也相似。我们的研究挑战了关于驱动对雄性生育力的有害影响的传统假设。这表明，SR 雄性的每一次射精的投资都已经调整到与野生型雄性的精子输送相匹配。我们根据最近的理论模型解释了这些结果，这些模型预测了当雄性在用于繁殖的资源或精子生育力方面存在差异时，射精策略如何进化。在减数分裂驱动已经持续了许多代的物种中，适应性补偿很可能会发生，并预测在野生种群中维持更高的稳定驱动频率。未来的研究必须确定驱动雄性如何补偿失败的精子发生，以及这种补偿如何与其他适应度特征的投资相权衡。
