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 raising larvae from the egg stage at different temperatures and photoperiods corresponding to different latitudes. 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 dynamics along the latitudinal gradients, but further experiments are needed to explore this.

研究背景：捕食作用广泛存在于自然界中。同类相食作为捕食作用的一种表现形式，其发生受体型结构、资源密度等多种因素调控。除此之外，同类相食还可能受到季节性时间限制等非生物因子的影响。由于高纬度地区的季节性时间限制更为严苛，该区域的同类相食行为可能更为强烈，但目前学界对同类相食的纬度变异规律几乎一无所知。本研究以横跨欧洲的纬度梯度上的狭翅豆娘（Lestes sponsa）幼虫为研究对象，通过将其卵期个体在匹配不同纬度的温度与光周期条件下饲养，探究了其同类相食行为与活动能力的变化。研究结果：我们发现，高纬度地区受季节性时间限制更强的种群，以及经历更严苛季节性时间限制的个体，其同类相食水平显著更高。同时，北纬度条件下的幼虫活动能力更强，且活动能力与同类相食水平呈显著正相关，这表明该行为是时间受限动物同类相食水平升高的介导机制。研究结论：本研究结果与经典的纬度-捕食格局相悖——该格局预测低纬度地区的捕食作用更强，但我们的研究显示高纬度地区的同类相食行为更为强烈。同类相食的纬度差异可能对纬度梯度上的种群动态产生潜在影响，但该推论仍需通过进一步实验进行验证。