Data from: Surrounding pathogens shape maternal egg care but not egg production in the European earwig

Pathogens are ubiquitous in nature and typically entail major fitness costs in their hosts. These costs can be particularly important when individuals exhibit poor immune defenses, as it is often the case during early developmental stages. Hence, selection should favor parental strategies limiting the risks of pathogen exposure and infection in their offspring. In this study, we investigated 1) whether females of the European earwig Forficula auricularia avoid areas contaminated with spores of the entomopathogenic fungus Metarhizium brunneum prior to and at egg laying, as well as 2) whether spore presence entails an increase in females’ investment into both pre-hatching forms of care and clutch quantity and quality. Our results first show that females did not avoid contaminated areas prior to and at egg laying. However, females returned to their eggs faster in presence of living spores compared to UV-killed or no spores. They were also more likely to construct a nest when in presence of both living and UV-killed spores (but only in one studied population). Finally, we found that spore presence did not influence maternal investment into egg grooming, egg gathering and egg defense, as well as into clutch quantity and quality. Overall, our results demonstrate that earwig females do not avoid contaminated environments, but could mitigate the associated costs of pathogen exposure by adjusting their level of egg care. These findings emphasize the importance of pathogens in the evolution of pre-hatching parental care and, more generally, in the emergence and maintenance of family life in nature.

病原体在自然界中无处不在，且通常会对宿主造成显著的生存适合度代价。当个体免疫防御能力较弱时，这类代价尤为凸显，而这一情况在个体发育早期阶段颇为常见。因此，自然选择应会青睐那些能够降低子代接触病原体并受其感染风险的亲本策略。本研究探究了两个核心问题：其一，欧洲蠼螋（Forficula auricularia）的雌虫在产卵前及产卵过程中，是否会避开被昆虫病原真菌布氏绿僵菌（Metarhizium brunneum）孢子污染的区域；其二，孢子的存在是否会促使雌虫增加对卵期抚育行为，以及卵团数量与质量的投入。研究结果首先表明，雌虫在产卵前及产卵过程中并未主动避开污染区域。但相较于紫外线灭活孢子组与无孢子对照组，雌虫在活孢子存在的环境中返回卵团的速度显著更快。此外，当环境中同时存在活孢子与紫外线灭活孢子时，雌虫筑巢的概率更高，但该现象仅在一个研究种群中被观测到。最后，本研究发现孢子的存在并不会影响雌虫对卵的梳理、卵的归集与卵的防御等母本抚育投入，也不会对卵团的数量与质量产生显著影响。综合来看，本研究结果表明，蠼螋雌虫并不会主动避开受污染的环境，但可通过调整卵期抚育强度来缓解病原体接触所带来的相关生存代价。这些研究结果凸显了病原体在卵期亲本抚育行为演化中的重要性，更广泛而言，也揭示了其在自然界中动物家庭生活的起源与维持过程中的关键作用。