Chemnitz Johanna, Bagrii Nadiia, Ayasse Manfred, Steiger Sandra
Institute of Evolutionary Ecology and Conservation Genomics, University of Ulm, 89081, Ulm, Germany.
Institute of Insect Biotechnology, University of Gießen, 35392, Giessen, Germany.
Naturwissenschaften. 2017 Aug;104(7-8):53. doi: 10.1007/s00114-017-1473-5. Epub 2017 Jun 15.
Life history theory predicts a trade-off between male sexual trait expression and immunocompetence. Using burying beetles, Nicrophorus vespilloides, as a model, we investigated the relationship between male immune function, sex pheromone emission, and attractiveness under field conditions. In the first experiment, we tested whether there is a positive correlation between immune capacity, sex pheromone characteristics (quantity, relative composition, and time invested in pheromone emission), and male attractiveness. As a measurement of immune capacity, we used an individual's encapsulation ability against a novel antigen. In the second experiment, we specifically examined whether a trade-off between chemical trait expression and immune function existed. To this end, we challenged the immune system and measured the subsequent investment in sex pheromone emission and the attractiveness of the male under field conditions. We found that a male's immunocompetence was neither related to the emission of the male's sex pheromone nor to its attractiveness in the field. Furthermore, none of the immune-challenge treatments affected the subsequent investment in pheromone emission or number of females attracted. However, we showed that the same males that emitted a high quantity of their sex pheromone in the laboratory were able to attract more females in the field. Our data suggest that the chemical signal is not a reliable predictor of a male's immunocompetence but rather is a general important fitness-related trait, with a higher emission of the sex pheromone measured in the laboratory directly affecting the attractiveness of a male under field conditions.
生活史理论预测，雄性性特征表达与免疫能力之间存在权衡。我们以埋葬虫（Nicrophorus vespilloides）为模型，研究了野外条件下雄性免疫功能、性信息素释放与吸引力之间的关系。在第一个实验中，我们测试了免疫能力、性信息素特征（数量、相对组成以及性信息素释放投入的时间）和雄性吸引力之间是否存在正相关。作为免疫能力的衡量指标，我们使用了个体对新抗原的包囊化能力。在第二个实验中，我们专门研究了化学特征表达与免疫功能之间是否存在权衡。为此，我们对免疫系统进行刺激，并测量随后在野外条件下雄性对性信息素释放的投入以及雄性的吸引力。我们发现，雄性的免疫能力既与雄性性信息素的释放无关，也与它在野外的吸引力无关。此外，任何免疫刺激处理都没有影响随后对性信息素释放的投入或吸引到的雌性数量。然而，我们发现，在实验室中释放大量性信息素的相同雄性在野外能够吸引更多雌性。我们的数据表明，化学信号不是雄性免疫能力的可靠预测指标，而是一个与适合度普遍相关的重要特征，在实验室中测得的性信息素释放量较高直接影响雄性在野外条件下的吸引力。
