Stav G, Blaustein L, Margalit Y
Center of Biological Control, Department of Biology, Ben-Gurion University, Beer-Sheva 84105 Israel.
J Vector Ecol. 2000 Dec;25(2):190-202.
We assessed the overall (consumptive plus non-consumptive) and non-consumptive effects of nymphal Anax imperator (Aeshnidae: Odonata) on experimental pool communities by comparing three treatments: (1) control (no Anax); (2) free Anax (Anax was not constrained); and (3) caged Anax (Anax, enclosed within a cage, could not consume prey outside the cages, but could possibly influence them via perceived risk of predation). Fewer egg rafts of the mosquito Culiseta longiareolata were found in the free Anax treatment compared to the other two treatments. There was no statistically significant difference in the number of egg rafts between control and caged Anax pools. Thus, while Culiseta females apparently oviposit fewer egg rafts in the presence of unconstrained Anax, they did not respond to predation risk from the caged Anax. Larval Culiseta densities were drastically reduced by free Anax; there was nearly a 100% reduction in the number reaching metamorphosis (pupae) and a 100% reduction in emergence (pupal exuviae). There were no significant treatment effects on densities of crustaceans, Daphnia magna and Heterocypris sp., or on chironomid pupal exuviae. Ceratopogonid pupal abundance was higher in free Anax pools than in the other two treatments toward the end of the experiment. Free Anax caused a trophic cascade, presumably by strongly reducing the dominant periphyton grazer, Culiseta larvae; periphyton mass was greater in the free Anax treatment than in the control. However, there was no behavioral trophic cascade, i.e., no difference in periphyton abundance between the control and caged Anax treatment.
我们通过比较三种处理方式，评估了豆娘（大斑晏蜓，蜓科：蜻蜓目）若虫对实验池塘群落的总体（消耗性加非消耗性）和非消耗性影响：（1）对照（无豆娘）；（2）自由豆娘组（豆娘不受限制）；（3）笼养豆娘组（豆娘被关在笼子里，无法捕食笼外猎物，但可能通过被捕食风险的感知影响猎物）。与其他两种处理方式相比，自由豆娘组中长跗库蚊的卵块数量更少。对照池塘和笼养豆娘池塘的卵块数量在统计学上没有显著差异。因此，虽然在自由豆娘存在的情况下，长跗库蚊雌性明显产卵的卵块较少，但它们对笼养豆娘的捕食风险没有反应。自由豆娘使长跗库蚊幼虫密度大幅降低；达到变态（蛹）阶段的数量几乎减少了100%，羽化（蛹蜕）数量减少了100%。对甲壳类动物、大型溞和奇异米虾的密度，或对摇蚊蛹蜕没有显著的处理效应。在实验接近尾声时，自由豆娘组的蠓蛹丰度高于其他两种处理方式。自由豆娘引发了营养级联效应，可能是通过大幅减少占主导地位的附生植物食草动物——长跗库蚊幼虫；自由豆娘处理组中的附生植物量比对照组更大。然而，没有行为营养级联效应，即对照处理和笼养豆娘处理之间的附生植物丰度没有差异。
