Data from: Cannibalism and activity rate in larval damselflies increase along a latitudinal gradient as a consequence of time constraints

Background: Predation is ubiquitous in nature. One form of predation is cannibalism, which is affected by many factors such as size structure and resource density. However, cannibalism may also be influenced by abiotic factors such as seasonal time constraints. Since time constraints are greater at high latitudes, cannibalism could be stronger at such latitudes, but we know next to nothing about latitudinal variation in cannibalism. In this study we examined cannibalism and activity in larvae of the damselfly Lestes sponsa, along a latitudinal gradient across Europe. We did this by performing a laboratory study where we raised larvae from the eggs stage and manipulated temperature and photoperiod. Results: We found that the more seasonally time-constrained populations in northern latitudes and individuals subjected to greater seasonal time constraints exhibited a higher level of cannibalism. We also found that activity was higher at north latitude conditions, and thus correlated with cannibalism, suggesting that this behaviour mediates higher levels of cannibalism in time-constrained animals. Conclusions: Our results go counter to the classical latitude-predation pattern which predicts higher predation at lower latitudes, since we found that predation was stronger at higher latitudes. The differences in cannibalism might have implications for population dynamic along the latitudinal gradients, but further experiments are needed to explore this.背景：捕食行为在自然界中普遍存在。同类相食（cannibalism）作为捕食的一种形式，其发生受体型结构、资源密度等多种因素调控。此外，同类相食还可能受到季节时间限制等非生物因素的影响。高纬度地区的季节时间限制更为严苛，理论上该区域的同类相食行为应更为强烈，但目前学界对同类相食的纬度变异几乎一无所知。本研究以横跨欧洲沿纬度梯度分布的豆娘（Lestes sponsa）幼虫为研究对象，探讨其同类相食与活动行为：通过实验室实验，从卵期开始饲养幼虫，并对温度与光周期进行精准操控。 结果：研究发现，高纬度地区受季节时间限制更强的种群，以及承受更严苛季节时间限制的个体，其同类相食水平显著更高。同时，高纬度环境下的幼虫活动能力更强，且活动水平与同类相食程度呈显著正相关，这表明行为活动是时间受限动物同类相食水平升高的介导因素。 结论：本研究结果与经典的纬度-捕食模式相悖——该经典模式预测低纬度地区捕食强度更高，但本研究发现高纬度地区的捕食（同类相食）强度更强。同类相食的纬度差异可能对沿纬度梯度分布的种群动态产生潜在影响，但相关推论仍需后续实验进一步验证。