Heo Jiman, Han Chang S
Department of Biology Kyung Hee University Seoul Korea.
Korea Institute of Ornithology Kyung Hee University Seoul Korea.
Ecol Evol. 2024 Nov 11;14(11):e70569. doi: 10.1002/ece3.70569. eCollection 2024 Nov.
Labile traits, such as behavioural, physiological traits or body mass, vary within an individual either over time or across environments. Such changes within an individual can be linked across traits, forming within-individual trait correlations. These correlations are particularly expected when ageing causes changes in the expression of multiple traits. Moreover, the direction of these correlations depends on mechanisms that explain age-related changes in each trait, such as physiological deterioration or changes in future fitness expectations. Therefore, assessing within-individual trait correlations offers insights into trait-specific ageing patterns, their integration and age-related reproductive strategies. Here, we tracked individual male cicadas () in their natural habitat, repeatedly assessing their plant use (narrow-leafed vs. large-leafed plants), calling activity and body mass. The results revealed that male cicadas lost mass, increased calling activity and a preference for narrow-leafed plants as they aged. This integration of age-related plasticity led to negative within-individual correlations between body mass and behaviours. Considering that adult cicadas consume nutritionally poor xylem sap, the negative within-individual correlations between body mass and risk-taking behaviour suggest that males follow a capital breeding strategy rather than an income breeding strategy. As adult cicadas may use up the energy stored during the nymph stage, an age-related increase in energetically demanding calling activity could cause an age-related decrease in body mass. The terminal investment hypothesis could also explain the age-related increase in calling activity and the preference for narrow-leafed plants. Therefore, we emphasise the importance of individual-level tracking studies in the wild to achieve a comprehensive understanding of the life-history strategies and behavioural ecology of a study animal.
不稳定的性状，如行为、生理特征或体重，会在个体内部随时间或跨环境而变化。个体内部的这种变化可能在不同性状之间存在关联，形成个体内性状相关性。当衰老导致多个性状的表达发生变化时，尤其会出现这些相关性。此外，这些相关性的方向取决于解释每个性状与年龄相关变化的机制，如生理衰退或未来适合度期望的变化。因此，评估个体内性状相关性有助于深入了解特定性状的衰老模式、它们的整合以及与年龄相关的繁殖策略。在这里，我们在自然栖息地追踪了雄性蝉个体，反复评估它们对植物的利用情况（窄叶植物与阔叶植物）、鸣叫活动和体重。结果显示，雄性蝉随着年龄增长体重下降、鸣叫活动增加，并且对窄叶植物的偏好增加。这种与年龄相关的可塑性整合导致了体重与行为之间的个体内负相关。考虑到成年蝉以营养贫乏的木质部汁液为食，体重与冒险行为之间的个体内负相关表明雄性蝉遵循的是资本繁殖策略而非收入繁殖策略。由于成年蝉可能会耗尽若虫阶段储存的能量，与年龄相关的高能量需求的鸣叫活动增加可能导致与年龄相关的体重下降。终端投资假说也可以解释与年龄相关的鸣叫活动增加以及对窄叶植物的偏好。因此，我们强调在野外进行个体水平追踪研究对于全面理解研究动物的生活史策略和行为生态学的重要性。
