Personality driven life-history trade-offs differ in two sub-populations of free ranging predators

1) Consistent individual differences in behaviour (i.e. personality) can be explained in an evolutionary context if they are favoured by life-history trade-offs as conceptualized in the pace-of-life syndrome (POLS) hypothesis. Theory predicts that faster growing individuals suffer higher mortality and that this trade-off is mediated through exploration/risk-taking personality, but empirical support for this remains limited and ambiguous. Equivocal support to the POLS hypothesis suggests that the link between life-history and personality may only emerge under certain circumstances. Understanding personality driven trade-offs would be facilitated by long-term studies in wild populations experiencing different ecological conditions. 2) Here, we tested whether personality measured in semi-captivity was associated with a growth-mortality trade-off via risk-taking in the wild in two sub-populations of juvenile lemon sharks (Negaprion brevirostris) known to differ in their predator abundance. We expected stronger personality driven trade-offs in the predator-rich environment as compared to the predator-poor environment. 3) Sharks were captured yearly from 1995 onwards allowing us to obtain long-term data on growth and apparent survival in each sub-population. We then used a novel open-field assay to test sharks for exploration personality yearly from 2012 to 2017. A subset of the tested sharks was monitored in the field using telemetry to document risk-taking behaviours. We tested (i) if fast explorers in captivity took more risks and grew faster in the wild and (ii) if natural selection acted against more explorative, faster growing sharks. 4) In the sub-population with fewer predators, more explorative sharks in captivity took more risks in the wild and grew faster. In turn, larger, fast-growing sharks had lower apparent survival. In the predator-rich sub-population, despite finding selection on fast growth, we found no link between exploration personality and the growth-mortality trade-off. 5) Our study demonstrates that the association between personality and life-history is favoured in some ecological contexts but not in others. We identify predator and resource abundance as two main potential drivers of the personality mediated trade-off and emphasize that future work on the POLS hypothesis would benefit from an approach integrating behaviour and life-history across ecological conditions.

1) 行为的一致性个体差异（即个性），若能如生活史节奏综合征（pace-of-life syndrome, POLS）假说所阐释的那样，通过生活史权衡获得青睐，则可在进化背景下得到解释。理论预测，生长速度更快的个体死亡率更高，且这种权衡由探索/冒险个性所介导，但相关实证支持迄今仍有限且模糊。针对POLS假说的模棱两可的支持表明，生活史与个性之间的关联或许仅在特定条件下才会显现。针对野生种群在不同生态条件下开展的长期研究，将有助于理解个性驱动的权衡机制。
2) 本研究针对两个捕食者丰度存在差异的幼柠檬鲨（Negaprion brevirostris）亚种群，检验了半圈养环境下测定的个性是否会通过野生环境中的冒险行为，与生长-死亡率权衡产生关联。我们预期，相较于捕食者匮乏的环境，在捕食者丰富的环境中，个性驱动的权衡效应会更为显著。
3) 研究团队自1995年起每年对鲨鱼进行捕获，从而获取了两个亚种群的生长及表观存活率长期数据。2012年至2017年，我们每年通过新型开放场实验测定鲨鱼的探索个性，并对其中一部分受试个体利用遥测技术进行野外监测，以记录其冒险行为。我们旨在检验两个假设：其一，圈养环境中探索性更强的个体，在野生环境中是否会更勇于冒险且生长速度更快；其二，自然选择是否会对探索性更强、生长速度更快的个体产生抑制作用。
4) 在捕食者较少的亚种群中，圈养环境下探索性更强的鲨鱼在野生环境中冒险行为更多，且生长速度更快。反之，体型更大、生长速度更快的鲨鱼表观存活率更低。而在捕食者丰富的亚种群中，尽管我们检测到了针对快速生长的选择压力，但并未发现探索个性与生长-死亡率权衡之间存在关联。
5) 本研究证实，个性与生活史之间的关联仅在部分生态环境中存在，而非所有环境。我们将捕食者与资源丰度确定为个性介导权衡的两大核心潜在驱动因素，并强调，未来针对POLS假说的研究若能整合不同生态条件下的行为与生活史数据，将更具学术价值。