Li Zhiwen, Yang Zhongxia, Li Youzhi
Hunan Provincial Key Laboratory for Biology and Control of Plant Diseases and Insect Pests, College of Plant Protection, Hunan Agricultural University, Changsha 410128, China.
Insects. 2022 Feb 28;13(3):246. doi: 10.3390/insects13030246.
The endoparasitoid body size hypothesis suggests that the size of larvae that develop in a single host should be subject to a trade-off: larger size could lead to increase overall fitness but could simultaneously increase the risk of resource depletion and starvation, resulting in a body size just below the host holding capacity. However, this hypothesis has not been rigorously tested using mathematical models thus far. The camellia weevil, (Coleoptera: Curculionidae), is a notorious pest attacking fruits of Abel. and Hu., in which the larvae develop within a single fruit and larval development is limited by the available food resources. We developed a feasible method to test this hypothesis. First, five models were used to describe the relationship between larval mass and host size. Then, the minimum fruit threshold that had to be met for ad libitum larval development and the corresponding larval size () of this threshold were calculated based on the characteristics of the optimal model. Finally, the difference between the measured larval size and the predicted larval size () was determined. The results showed that (1) the data were better described by a logistic function than any other equation; (2) larval size in both host plants increased with increasing fruit size until leveling off when the fruits were large enough to allow unconstrained larval development; (3) larval size remained just below the host-fruit holding capacity, as there was no difference between the measured and predicted larval sizes (); and (4) larvae developed in host plant with larger fruits had a larger size. These results confirmed the endoparasitoid body size hypothesis.
内寄生蜂体型假说认为，在单个宿主体内发育的幼虫大小应存在一种权衡：体型较大可能会提高整体适合度，但同时可能会增加资源耗尽和饥饿的风险，导致体型刚好低于宿主容纳能力。然而，到目前为止，这一假说尚未通过数学模型进行严格验证。油茶象（鞘翅目：象甲科）是一种臭名昭著的害虫，会侵害油茶叶片和果实，其幼虫在单个果实内发育，幼虫发育受可用食物资源限制。我们开发了一种可行的方法来验证这一假说。首先，使用五个模型来描述幼虫质量与宿主大小之间的关系。然后，根据最优模型的特征，计算幼虫自由发育所需满足的最小果实阈值以及该阈值对应的幼虫大小（）。最后，确定实测幼虫大小与预测幼虫大小（）之间的差异。结果表明：（1）与其他任何方程相比，逻辑函数能更好地描述数据；（2）两种宿主植物中的幼虫大小均随果实大小增加而增加，直到果实足够大允许幼虫自由发育时趋于平稳；（3）幼虫大小刚好低于宿主果实容纳能力，因为实测幼虫大小与预测幼虫大小（）之间没有差异；（4）在果实较大的宿主植物中发育的幼虫体型更大。这些结果证实了内寄生蜂体型假说。
