Menu Frédéric, Desouhant Emmanuel
UMR CNRS 5558, Biométrie et Biologie Evolutive, Université Claude Bernard Lyon I, 43, Boulevard du 11 novembre 1918, 69622, Villeurbanne Cedex, France.
Oecologia. 2002 Jul;132(2):167-174. doi: 10.1007/s00442-002-0969-6. Epub 2002 Jul 1.
Diversified bet-hedging for life cycle duration is defined as within-generation variability in cycle length expressed by a single genotype maximising mean geometric fitness. Such plasticity is not predictive, i.e. it is not a response to cues from the environment that has a predictive value for the decision at hand. In evolutionary terms, diversified bet-hedging is perceived as an adaptation to environmental stochasticity. However, clear evidence of bet-hedging is scarce and exists only for a few desert plant species and one desert bee. In temperate insects, diversified bet-hedging for life cycle duration has been suspected in the chestnut weevil, but proximate factors responsible for individual variation are still unknown. From field experiments, we show that the frequency of the long cycle depends on larval weight and on the date when a larva abandons the fruit, but not on larval burying depth in the soil. Since the two first factors are known to depend on food and temperature and cannot lead to predictive plasticity, we give evidence of bet hedging in this temperate species. Indeed, despite a cost associated with prolonged diapause (extra mortality and loss of reproductive opportunity), a previous study showed that plasticity for life cycle duration, such as discussed in this paper, maximises mean geometric fitness and persistence probability in the chestnut weevil. We propose the hypothesis that the variation in life cycle duration depends on individual variability of metabolic resources such as lipids.
生命周期持续时间的多样化风险对冲被定义为单个基因型所表现出的世代内周期长度变异性，这种变异性使平均几何适合度最大化。这种可塑性是不可预测的，也就是说，它不是对具有当前决策预测价值的环境线索的反应。从进化的角度来看，多样化风险对冲被视为对环境随机性的一种适应。然而，风险对冲的明确证据很少，仅存在于少数沙漠植物物种和一种沙漠蜜蜂中。在温带昆虫中，栗实象鼻虫被怀疑存在生命周期持续时间的多样化风险对冲，但导致个体变异的近端因素仍然未知。通过田间实验，我们表明长周期的频率取决于幼虫体重和幼虫离开果实的日期，而不取决于幼虫在土壤中的埋藏深度。由于已知前两个因素取决于食物和温度，且不会导致可预测的可塑性，我们提供了这种温带物种存在风险对冲的证据。事实上，尽管延长滞育存在成本（额外死亡率和繁殖机会丧失），但先前的一项研究表明，本文所讨论的生命周期持续时间的可塑性在栗实象鼻虫中使平均几何适合度和持续概率最大化。我们提出一个假设，即生命周期持续时间的变化取决于脂质等代谢资源的个体变异性。
