Data from: Harvested populations are more variable only in more variable environments

The interaction between environmental variation and population dynamics is of major importance, particularly for managed and economically important species, and especially given contemporary changes in climate variability. Recent analyses of exploited animal populations contested whether exploitation or environmental variation has the greatest influence on the stability of population dynamics, with consequences for variation in yield and extinction risk. Theoretical studies however have shown that harvesting can increase or decrease population variability depending on environmental variation, and requested controlled empirical studies to test predictions. Here, we use an invertebrate model species in experimental microcosms to explore the interaction between selective harvesting and environmental variation in food availability in affecting the variability of stage-structured animal populations over 20 generations. In a constant food environment, harvesting adults had negligible impact on population variability or population size, but in the variable food environments, harvesting adults increased population variability and reduced its size. The impact of harvesting on population variability differed between proportional and threshold harvesting, between randomly and periodically varying environments, and at different points of the time series. Our study suggests that predicting the responses to selective harvesting is sensitive to the demographic structures and processes that emerge in environments with different patterns of environmental variation.

环境变异与种群动态之间的相互作用至关重要，尤其针对受管理（managed）及具有经济价值的物种而言，在当前气候变异持续演变的背景下这一问题尤为关键。近期针对开发利用中的动物种群的相关分析，就捕捞活动与环境变异二者何者对种群动态稳定性的影响更大这一议题产生了争议，该争议将对产量波动与灭绝风险产生连锁效应。然而，理论研究显示，捕捞对种群变异性的影响可能增强或减弱种群变异性，具体取决于环境变异状况，同时学界呼吁开展可控的实证研究以验证相关预测。本研究借助实验微宇宙（experimental microcosms）中的无脊椎动物模式物种，探究了选择性捕捞与食物可获得性的环境变异之间的相互作用，该相互作用会影响20代内阶段结构型（stage-structured）动物种群的变异性。在恒定食物环境中，捕捞成体对种群变异性或种群规模几乎无显著影响；但在可变食物环境中，捕捞成体则会提升种群变异性并降低种群规模。捕捞对种群变异性的影响存在差异：在比例捕捞（proportional harvesting）与阈值捕捞（threshold harvesting）策略之间、随机波动环境与周期性波动环境之间，以及时间序列的不同阶段均表现出不同的影响效果。本研究表明，对选择性捕捞的响应预测，会因不同环境变异模式下所形成的种群结构与动态过程而异。