Variation in age and mass at maturity is commonly observed in populations, even among individuals with the same genetic and environmental backgrounds. Accounting for such individual variation with a stochastic model is important for estimating optimal evolutionary strategies and for understanding potential trade-offs among life-history traits. However, most studies employ stochastic models that are either phenomenological or account for variation in only one life-history trait. We propose a model based on the developmental biology of the moth Manduca sexta that accounts for stochasticity in two key life-history traits, age and mass at maturity. The model is mechanistic, describing feeding behavior and common insect developmental processes, including the degradation of juvenile hormone prior to molting. We derive a joint probability density function for the model and explore how the distribution of age and mass at maturity is affected by different parameter values. We find that the joint distribution is generally nonnormal and highly sensitive to parameter values. In addition, our model predicts previously observed effects of temperature change and nutritional quality on the expected values of insect age and mass. Our results highlight the importance of integrating multiple sources of stochasticity into life-history models.

中文翻译：

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预测昆虫成熟期的年龄和质量的随机模型。

在人口中，甚至在具有相同遗传和环境背景的个体中，通常会观察到成熟时年龄和质量的变化。用随机模型说明这种个体差异对于估计最佳进化策略和理解生命历史特征之间的潜在权衡非常重要。但是，大多数研究采用的是现象学的随机模型，或仅解释一种生活历史特征的变异。我们提出了基于蛾的发育生物学模型烟草天蛾这是两个主要生命历史特征（年龄和成熟时的质量）中的随机性。该模型是机械的，描述了进食行为和常见的昆虫发育过程，包括蜕皮前幼体激素的降解。我们为该模型导出联合概率密度函数，并探讨不同参数值如何影响成熟时年龄和质量的分布。我们发现关节分布通常是非正态的，并且对参数值高度敏感。此外，我们的模型预测了温度变化和营养质量对昆虫年龄和质量预期值的先前观察到的影响。我们的结果强调了将随机性的多种来源整合到生活史模型中的重要性。