Studying alternative forms of reproduction in natural populations is of fundamental importance for understanding the costs and benefits of sex. Mayflies are one of the few animal groups where sexual reproduction co-occurs with different types of parthenogenesis, providing ideal conditions for identifying benefits of sex in natural populations. Here, we establish a catalog of all known mayfly species capable of reproducing by parthenogenesis, as well as species unable to do so. Overall, 1.8% of the described species reproduce parthenogenetically, which is an order of magnitude higher than reported in other animal groups. This frequency even reaches 47.8% if estimates are based on the number of studied rather than described mayfly species, as reproductive modes have thus far been studied in only 17 out of 42 families. We find that sex is a more successful strategy than parthenogenesis (associated with a higher hatching success of eggs), with a trade-off between the hatching success of parthenogenetic and sexual eggs. This means that improving the capacity for parthenogenesis may come at a cost for sexual reproduction. Such a trade-off can help explain why facultative parthenogenesis is extremely rare among animals despite its potential to combine the benefits of sexual and parthenogenetic reproduction. We argue that parthenogenesis is frequently selected in mayflies in spite of this probable trade-off because their typically low dispersal ability and short and fragile adult life may frequently generate situations of mate limitation in females. Mayflies are currently clearly underappreciated for understanding the benefits of sex under natural conditions.

中文翻译：

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蜉蝣（蜉蝣目）极其广泛的孤雌生殖和替代繁殖形式之间的权衡

研究自然种群中的替代生殖形式对于理解性的成本和收益至关重要。蜉蝣是有性生殖与不同类型的孤雌生殖同时发生的少数动物群体之一，为识别自然种群中性的益处提供了理想的条件。在这里，我们建立了所有已知能够通过孤雌生殖繁殖的蜉蝣物种以及不能这样做的物种的目录。总体而言，所描述的物种中有 1.8% 采用孤雌生殖方式繁殖，这比其他动物群体中报道的要高一个数量级。如果估计是基于研究的蜉蝣物种的数量而不是描述的蜉蝣物种，那么这一频率甚至会达到 47.8%，因为迄今为止仅在 42 个科中的 17 个科中研究了繁殖模式。我们发现，有性生殖是比孤雌生殖（与更高的卵孵化成功率相关）更成功的策略，需要在孤雌生殖卵的孵化成功率和有性卵的孵化成功率之间进行权衡。这意味着提高孤雌生殖的能力可能会以有性生殖为代价。这种权衡可以帮助解释为什么兼性孤雌生殖在动物中极为罕见，尽管它有可能结合有性生殖和孤雌生殖的好处。我们认为，尽管存在这种可能的权衡，但蜉蝣仍经常选择单性生殖，因为它们典型的低扩散能力和短暂而脆弱的成年寿命可能经常导致雌性的交配限制。目前，蜉蝣在了解自然条件下性交的好处方面显然没有得到充分的重视。