Data from: Interacting effects of predation risk and resource level on escape speed of amphibian larvae along a latitudinal gradient

Fast-growing genotypes living in time-constrained environments are often more prone to predation, suggesting that growth-predation risk trade-offs are important factors maintaining variation in growth along climatic gradients. However, the mechanisms underlying how fast growth increases predation-mediated mortality are not well understood. Here, we investigated if slow-growing, low-latitude individuals have faster escape swimming speed than fast-growing high-latitude individuals using common frog (Rana temporaria) tadpoles from eight populations collected along a 1500 km latitudinal gradient. We measured escape speed in terms of burst and endurance speeds in tadpoles raised in the laboratory at two food levels and in the presence and absence of a predator (Aeshna dragonfly larvae). We did not find any latitudinal trend in escape speed performance. In low food treatments, burst speed was higher in tadpoles reared with predators but did not differ between high food treatments. Endurance speed, on the contrary, was lower in high-food tadpoles reared with predators, and did not differ between treatments at low food levels. Tadpoles reared with predators showed inducible morphology (increased relative body size and tail depth), which had positive effects on speed endurance at low but not at high food levels. Burst speed was positively affected by tail length and tail muscle size in the absence of predators. Our results suggest that escape speed does not trade off with fast growth along the latitudinal gradient in R. temporaria tadpoles. Instead, escape speed is a plastic trait and strongly influenced by the interaction between resource level and predation risk.

栖息于时间受限生境的快速生长基因型往往更易遭受捕食，这表明生长-捕食风险权衡（growth-predation risk trade-offs）是维持气候梯度下生长变异的关键驱动因素。然而，当前学界对快速生长如何提升捕食介导死亡率的内在机制仍知之甚少。
本研究以沿1500公里纬度梯度采集的8个种群的普通林蛙（Rana temporaria）蝌蚪为实验材料，旨在探究低纬度慢生长个体的逃逸游泳速度是否快于高纬度快生长个体。我们在实验室条件下设置了两种食物水平，并分别构建有捕食者（晏蜓（Aeshna）蜻蜓幼虫）与无捕食者的培养环境，对蝌蚪的爆发游泳速度与耐久游泳速度进行了量化测定。
实验未发现逃逸速度性能存在显著的纬度梯度趋势。在低食物处理组中，与捕食者共存的蝌蚪爆发速度更高，但该差异在高食物处理组中并未显现。与之相反，高食物水平且暴露于捕食者环境的蝌蚪耐久速度更低，而低食物水平下各处理组的耐久速度无显著差异。
与捕食者共存的蝌蚪呈现出诱导形态型——相对体型增大、尾高增加，该形态特征在低食物水平下对耐久速度具有显著正向影响，但在高食物水平下无此效应。在无捕食者的环境中，尾长与尾肌大小对爆发速度具有显著正向作用。
本研究结果表明，普通林蛙蝌蚪的逃逸速度并未沿纬度梯度与快速生长形成权衡关系。相反，逃逸速度属于可塑性性状，其表达强烈受资源水平与捕食风险的交互作用调控。