Campbell Stuart A, Stastny Michael
Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY, 14853, USA.
Department of Entomology, Cornell University, Ithaca, NY, 14853, USA.
Oecologia. 2015 Mar;177(3):715-721. doi: 10.1007/s00442-014-3141-1. Epub 2014 Nov 16.
Gregarious feeding is a common feature of herbivorous insects and can range from beneficial (e.g. dilution of predation risk) to costly (e.g. competition). Group age structure should influence these costs and benefits, particularly when old and young larvae differ in their feeding mode or apparency to predators. We investigated the relative value of gregarious feeding by aposematic larvae of Uresiphita reversalis that we observed feeding in groups of mixed ages and variable densities on wild Lupinus diffusus. In a manipulative field experiment, the survivorship and growth of young larvae were enhanced in the presence of older conspecifics, but not in large groups of similarly aged larvae. Estimates of insect damage and induced plant responses suggest that mixed-age groups enhance plant quality for young larvae while avoiding competition. We conclude that benefits of gregariousness in this species are contingent on group age structure, a finding of significance for the ecology and evolution of gregariousness and other social behaviours.
群居取食是食草昆虫的一个常见特征，其影响范围从有益（例如降低被捕食风险）到有害（例如竞争）。群体年龄结构应该会影响这些成本和收益，尤其是当幼虫的年龄不同，其取食方式或对捕食者的明显程度也不同时。我们研究了棉大卷叶螟警戒色幼虫群居取食的相对价值，我们观察到它们在野生散生羽扇豆上以不同年龄和密度的群体形式取食。在一项控制性田间实验中，在有大龄同种个体存在的情况下，幼虫的存活率和生长得到了提高，但在年龄相近的大群体中则没有。对昆虫损害和诱导植物反应的估计表明，不同年龄群体提高了幼虫的植物质量，同时避免了竞争。我们得出结论，该物种群居的益处取决于群体年龄结构，这一发现对于群居性及其他社会行为的生态学和进化具有重要意义。
