Jog Maithili M, Watve Milind G
Department of Microbiology, Abasaheb Garware College, Karve Road, Pune 411 004, India.
BMC Ecol. 2005 Feb 22;5:3. doi: 10.1186/1472-6785-5-3.
For parasites with a predator-prey life cycle, the completion of the life cycle often depends on consumption of parasitized prey by the predator. In the case of such parasite species the predator and the parasite have common interests and therefore a mutualistic relationship is possible. Some evidence of a predator-parasite mutualism was reported from spotted deer or chital (Axix axis) as a prey species, dhole or Indian wild-dog (Cuon alpinus) as the predator and a protozoan (Sarcocystis axicuonis) as the parasite. We examine here, with the help of a model, the ecological conditions necessary for the evolution and stability of such a mutualistic relationship. A two - level game theory model was designed in which the payoff of a parasite is decided not only by alternative parasite strategies but also by alternative host strategies and vice versa. Conditions for ESS were examined.
A tolerant predator strategy and a low or moderately virulent parasite strategy which together constitute mutualism are stable only at a high frequency of recycling of parasite and a substantial prey - capture benefit to the predator. Unlike the preliminary expectation, parasite will not evolve towards reduced virulence, but reach an optimum moderate level of virulence.
The available data on the behavioral ecology of dhole and chital suggest that they are likely to meet the stability criteria and therefore a predator-parasite mutualism can be stable in this system. The model also points out the gaps in the current data and could help directing further empirical work.
对于具有捕食者 - 猎物生命周期的寄生虫而言，生命周期的完成通常取决于捕食者对被寄生猎物的摄取。就此类寄生虫物种而言，捕食者与寄生虫有着共同利益，因此可能存在互利共生关系。有证据表明，作为猎物的花鹿或斑鹿（印度花鹿）、作为捕食者的豺或印度野犬以及作为寄生虫的一种原生动物（轴囊尾蚴）之间存在捕食者 - 寄生虫互利共生关系。在此，我们借助一个模型来研究这种互利共生关系进化与稳定所需的生态条件。设计了一个两级博弈论模型，其中寄生虫的收益不仅取决于寄生虫的替代策略，还取决于宿主的替代策略，反之亦然。研究了ESS的条件。
一种宽容的捕食者策略和一种低毒或中等毒力的寄生虫策略共同构成互利共生关系，这种关系仅在寄生虫高频率循环以及捕食者获得大量猎物捕获收益的情况下才稳定。与初步预期不同的是，寄生虫不会朝着降低毒力的方向进化，而是会达到一个最佳的中等毒力水平。
关于豺和花鹿行为生态学的现有数据表明，它们可能符合稳定性标准（因此捕食者 - 寄生虫互利共生关系在这个系统中可能是稳定的）。该模型还指出了当前数据中的差距，并有助于指导进一步的实证研究工作。
