Department of Zoology, University of Cambridge, Cambridge, UK.
School of Biological Sciences, University of Bristol, Bristol, UK.
J Evol Biol. 2020 Dec;33(12):1725-1734. doi: 10.1111/jeb.13711. Epub 2020 Oct 18.
Early-life conditions have been shown to have a profound effect on an animal's body size and fecundity across diverse taxa. However, less is known about how early-life effects on fecundity within each sex interact to determine reproductive success. We used experiments with burying beetles Nicrophorus vespilloides to analyse this problem. The nutritional conditions experienced by burying beetles in early life are a key determinant of adult body size in both sexes, and adult body size in turn influences male reproductive tactics. In previous work, we showed that smaller males are more effective than larger males at stimulating virgin female fecundity. In this study, we manipulated male and female body size by restricting access to food in early development. We then conducted breeding assays, in which small and large females were mated sequentially with small and large males, and then allowed to raise offspring without paternal care. We tested whether large females, which are potentially more fecund, laid even more eggs when mated with small males. We found no evidence to support this prediction. Instead, we detected only a weak non-significant trend in the predicted direction and no equivalent trend in the number of larvae produced. However, we did find that larvae attained a greater mass by the end of development when their mother was large and mated with a small male first. We suggest that large females might have evolved counter-measures that prevent exploitation by small fecundity-stimulating males, including partial filial cannibalism. By eating surplus larvae during reproduction, larger females would leave more of the carrion for their offspring to consume. This could explain why their surviving larvae are able to attain a greater mass by the time they complete their development.
早期生活条件被证明对不同分类群的动物的体型和繁殖力有深远的影响。然而，对于每个性别中早期生活对繁殖力的影响如何相互作用以决定繁殖成功，人们知之甚少。我们使用埋葬甲虫 Nicrophorus vespilloides 的实验来分析这个问题。埋葬甲虫在早期生活中经历的营养条件是决定雌雄成虫体型的关键因素，而成虫体型反过来又影响雄性的繁殖策略。在之前的工作中，我们表明，较小的雄性比较大的雄性更有效地刺激处女雌性的繁殖力。在这项研究中，我们通过限制早期发育过程中的食物获取来操纵雄性和雌性的体型。然后，我们进行了繁殖试验，其中小体型和大体型的雌性与小体型和大体型的雄性依次交配，然后在没有雄性照顾的情况下让它们抚养后代。我们测试了大体型雌性，它们可能更具繁殖力，当与小体型雄性交配时是否会产下更多的卵。我们没有发现证据支持这一预测。相反，我们只检测到一个微弱的、没有统计学意义的趋势，而在幼虫数量方面则没有类似的趋势。然而，我们确实发现，当母亲体型较大且首先与体型较小的雄性交配时，幼虫在发育结束时达到更大的质量。我们认为，大体型雌性可能已经进化出了一些对策，以防止被小的繁殖力刺激的雄性利用，包括部分亲代同类相食。通过在繁殖过程中吃掉多余的幼虫，体型较大的雌性会为其后代留下更多的腐肉供其食用。这可以解释为什么它们存活的幼虫在完成发育时能够达到更大的质量。
