Testing the link between perceived and actual risk of predation: mosquito oviposition site selection and egg predation by native and introduced fish

1. According to the threat-sensitivity hypothesis, prey avoidance behaviour should reflect the magnitude of predation risk. Since predation can strongly affect reproduction success, ovipositing females are expected to adaptively adjust their predator-avoidance response, or local breeding patch selectivity, in accordance with the perceived level of threat posed for their progeny by specific predators. However, association between avoidance and predation can be disrupted when the prey and the predator lack spatio-temporal opportunities to co-evolve, such as in cases of non-native predator introductions. 2. We examined the interactions between mosquitoes (from the genus Culex) and three species of sympatric predaceous freshwater fish, a native cyprinid (Barbus paludinosus), a cichlid (Pseudocrenilabrus philander), and an introduced poeciliid, the Western mosquitofish (Gambusia affinis). 3. In an outdoor mesocosm experiment we quantified patterns of Culex oviposition site selection across fish species using free-roaming, caged, and fish-free treatments. In a complementary laboratory experiment we tested the effectiveness of each fish species as predators of mosquito eggs and larvae. 4. Synthesis and applications. We found evidence for: (i) mosquito egg raft predation by free- roaming fish; (ii) fish-specific avoidance by ovipositing Culex and (iii) a positive association between fish-specific oviposition avoidance and fish-specific efficiency as an egg predator. These results contribute towards a better understanding of predator-prey coevolution, predator-borne cue recognition, and suggest local native fish, the Southern mouthbrooder (Pseudocrenilabrus philander), as an alternative to Gambusia for the biocontrol of Culex mosquitoes.1. 依据威胁敏感性假说（threat-sensitivity hypothesis），猎物的避敌行为应当能够反映其面临的捕食风险等级。由于捕食作用会显著影响繁殖成功率，因此产卵雌体应能根据特定捕食者对其后代构成的感知威胁水平，适应性地调控自身的避敌响应或局部繁殖斑块选择性。然而，当猎物与捕食者缺乏协同进化的时空机遇时（如外来捕食者引入事件中），避敌行为与捕食风险之间的关联会被打破。 2. 本研究针对库蚊属（Culex）蚊子与三种同域捕食性淡水鱼类的相互作用展开探究，这三种鱼类分别为本土鲤科鱼类（Barbus paludinosus）、慈鲷科鱼类（Pseudocrenilabrus philander），以及引入的花鳉科鱼类——西部食蚊鱼（Gambusia affinis）。 3. 在室外中宇宙实验（mesocosm experiment）中，我们通过设置自由活动组、笼养组与无鱼对照组，量化了不同鱼类条件下库蚊的产卵位点选择模式。配套开展的室内实验则检验了每种鱼类作为蚊卵与幼虫捕食者的捕食效率。 4. 综合与应用。本研究获得如下证据：（1）自由活动鱼类可捕食蚊卵浮筏；（2）产卵库蚊会表现出鱼类特异性避敌行为；（3）鱼类特异性产卵避敌行为与其作为卵捕食者的捕食效率呈正相关关系。上述结果有助于深化对捕食者-猎物协同进化、捕食者来源信号识别的认知，同时表明本土鱼类南方口育慈鲷（Pseudocrenilabrus philander）可作为西部食蚊鱼（Gambusia affinis）的替代方案，用于库蚊属蚊子的生物防治。