Does Sex-Selective Predation Stabilize or Destabilize Predator-Prey Dynamics?

BackgroundLittle is known about the impact of prey sexual dimorphism on predator-prey dynamics and the impact of sex-selective harvesting and trophy hunting on long-term stability of exploited populations.
Methodology and Principal FindingsWe review the quantitative evidence for sex-selective predation and study its long-term consequences using several simple predator-prey models. These models can be also interpreted in terms of feedback between harvesting effort and population size of the harvested species under open-access exploitation. Among the 81 predator-prey pairs found in the literature, male bias in predation is 2.3 times as common as female bias. We show that long-term effects of sex-selective predation depend on the interplay of predation bias and prey mating system. Predation on the ‘less limiting’ prey sex can yield a stable predator-prey equilibrium, while predation on the other sex usually destabilizes the dynamics and promotes population collapses. For prey mating systems that we consider, males are less limiting except for polyandry and polyandrogyny, and male-biased predation alone on such prey can stabilize otherwise unstable dynamics. On the contrary, our results suggest that female-biased predation on polygynous, polygynandrous or monogamous prey requires other stabilizing mechanisms to persist.
Conclusions and SignificanceOur modelling results suggest that the observed skew towards male-biased predation might reflect, in addition to sexual selection, the evolutionary history of predator-prey interactions. More focus on these phenomena can yield additional and interesting insights as to which mechanisms maintain the persistence of predator-prey pairs over ecological and evolutionary timescales. Our results can also have implications for long-term sustainability of harvesting and trophy hunting of sexually dimorphic species.

研究背景：目前学界对猎物性二态性（sexual dimorphism）对捕食者-猎物动态（predator-prey dynamics）的影响，以及选择性捕捞（sex-selective harvesting）与战利品狩猎（trophy hunting）对被开发种群（exploited populations）长期稳定性的影响均缺乏深入认知。

研究方法与主要发现：本研究综述了选择性捕食的定量研究证据，并通过数个简单的捕食者-猎物模型探究其长期效应。此类模型亦可用于阐释开放准入式开发（open-access exploitation）情境下，捕捞努力量与被开发物种种群规模之间的反馈关系。在文献收录的81组捕食者-猎物配对案例中，雄性偏向捕食的发生频率是雌性偏向捕食的2.3倍。本研究表明，选择性捕食的长期效应取决于捕食偏向与猎物交配系统（mating system）的相互作用。对“限制作用较弱的”猎物性别进行捕食，可形成稳定的捕食者-猎物平衡态；而对另一性别猎物的捕食通常会破坏动态稳定性，加剧种群崩溃。在本研究考量的猎物交配系统中，除一妻多夫制（polyandry）与多偶混交制（polyandrogyny）外，雄性均为限制作用较弱的性别；仅对这类猎物实施雄性偏向捕食，可使原本不稳定的种群动态趋于稳定。与之相反，本研究结果显示，对一夫多妻制（polygynous）、多配制（polygynandrous）或单配制（monogamous）的猎物实施雌性偏向捕食时，需借助其他稳定机制才能维持种群存续。

结论与意义：本研究的建模结果表明，学界观测到的雄性偏向捕食现象，除性选择（sexual selection）的影响外，还可能反映了捕食者-猎物相互作用的演化历史。若对这类现象给予更多关注，可进一步揭示在生态与演化时间尺度上维持捕食者-猎物配对存续的具体机制，从而获得更多富有价值的研究见解。本研究结果同时可为性二态性物种的捕捞与战利品狩猎的长期可持续性提供理论参考。