Institute of Organismic and Molecular Evolutionary Biology, Johannes-Gutenberg University of Mainz, Mainz, Germany.
Institut de Recherche sur la Biologie de l'Insecte, UMR 7261, CNRS, François-Rabelais University of Tours, Tours, France.
Sci Rep. 2017 Aug 11;7(1):7988. doi: 10.1038/s41598-017-08339-6.
Investigating the expression of trade-offs between key life-history functions is central to our understanding of how these functions evolved and are maintained. However, detecting trade-offs can be challenging due to variation in resource availability, which masks trade-offs at the population level. Here, we investigated in the European earwig Forficula auricularia whether (1) weapon size trades off with three key immune parameters - hemocyte concentration, phenoloxidase and prophenoloxidase activity - and whether (2) expression and strength of these trade-offs depend on male body condition (body size) and/or change after an immune challenge. Our results partially confirmed condition dependent trade-offs between weapon size and immunity in male earwigs. Specifically, we found that after an immune challenge, weapon size trades off with hemocyte concentrations in low-condition, but not in good-condition males. Contrastingly, weapon size was independent of pre-challenge hemocyte concentration. We also found no trade-off between weapon size and phenoloxidase activity, independent of body condition and immune challenge. Overall, our study reveals that trade-offs with sexual traits may weaken or disappear in good-condition individuals. Given the importance of weapon size for male reproductive success, our results highlight how low-condition individuals may employ alternative life-history investment strategies to cope with resource limitation.
研究关键生活史功能之间的权衡关系对于我们理解这些功能是如何进化和维持的至关重要。然而，由于资源可利用性的变化，在种群水平上掩盖了权衡关系，因此检测权衡关系具有挑战性。在这里，我们研究了欧洲耳夹子 Forficula auricularia 是否存在（1）武器大小与三个关键免疫参数 - 血细胞浓度、酚氧化酶和原酚氧化酶活性之间的权衡关系，以及（2）这些权衡关系的表达和强度是否取决于雄性身体状况（体型）和/或在免疫挑战后发生变化。我们的研究结果部分证实了雄性耳夹子中武器大小与免疫之间存在条件依赖性权衡关系。具体而言，我们发现，在免疫挑战后，低条件雄性的武器大小与血细胞浓度之间存在权衡关系，但在良好条件雄性中不存在这种关系。相反，武器大小与免疫挑战前的血细胞浓度无关。我们还发现，无论身体状况和免疫挑战如何，武器大小与酚氧化酶活性之间都不存在权衡关系。总的来说，我们的研究表明，与性特征相关的权衡关系可能在身体状况良好的个体中减弱或消失。鉴于武器大小对雄性生殖成功的重要性，我们的研究结果强调了低条件个体如何采用替代的生活史投资策略来应对资源限制。
