Sexual reproduction is ubiquitous in eukaryotes, but the mechanisms by which sex is determined are diverse and undergo rapid turnovers in short evolutionary timescales. Usually, an embryo’s sex is fated at the moment of fertilisation, but in rare instances it is the maternal genotype that determines the offspring’s sex. These systems are often characterised by mothers producing single-sex broods, a phenomenon known as monogeny. Monogenic reproduction is well documented in Hymenoptera (ants, bees and wasps), where it is associated with a eusocial lifestyle. However, it is also known to occur in three families in Diptera (true flies): Sciaridae, Cecidomyiidae and Calliphoridae. Here we review current knowledge of monogenic reproduction in these dipteran clades. We discuss how this strange reproductive strategy might evolve, and we consider the potential contributions of inbreeding, sex ratio distorters, and polygenic control of the sex ratio. Finally, we provide suggestions on future work to elucidate the origins of this unusual reproductive strategy. We propose that studying these systems will contribute to our understanding of the evolution and turnover of sex determination systems.

有性生殖在真核生物中普遍存在，但决定性别的机制多种多样，并且在较短的进化时间尺度内经历快速更替。通常，胚胎的性别在受精时就已注定，但在极少数情况下，是母亲的基因型决定了后代的性别。这些系统的特点通常是母亲产下单性幼崽，这种现象称为单性生殖。单基因繁殖在膜翅目（蚂蚁、蜜蜂和黄蜂）中已有充分记录，与真社会生活方式相关。然而，它也存在于双翅目（真蝇）的三个科中：Sciaridae、Cecidomyyiidae 和 Calliphoridae。在这里，我们回顾了这些双翅目进化枝中单基因繁殖的最新知识。我们讨论这种奇怪的繁殖策略可能如何演变，我们还考虑了近亲繁殖、性别比例扭曲和性别比例多基因控制的潜在贡献。最后，我们对未来的工作提出建议，以阐明这种不寻常的繁殖策略的起源。我们建议研究这些系统将有助于我们理解性别决定系统的进化和更替。