Ectothermic omnivores increase herbivory in response to rising temperature

Higher temperatures as a consequence of global climate change may considerably alter trophic interactions. Ectothermic herbivores and carnivores generally ingest more food with rising temperature as their metabolic rates increase with rising temperature. However, omnivorous ectotherms may respond in two ways: quantitatively by consuming more food and qualitatively by altering their degree of herbivory or carnivory through a diet shift. We hypothesize that rising temperature will increase herbivory of ectothermic omnivores as herbivory increases towards the equator. We tested the hypothesis in a freshwater model system in which ectothermic omnivores are prevalent, by applying two approaches, a temperature manipulation experiment and a literature study. We performed feeding trials with a juvenile aquatic ectothermic omnivore (pond snail Lymnaea stagnalis) at different temperatures ranging from 12 to 27°C, supplying them with both animal food and plant material, and directly quantified the...全球气候变化引发的气温升高，可能会显著改变营养级互作（trophic interactions）关系。外温性（ectothermic）植食动物与肉食动物通常会随气温升高摄入更多食物，因其代谢速率随温度上升而提升。不过，杂食性外温动物（ectothermic omnivores）则存在两种响应模式：一是在数量层面增加食物摄入量，二是在质量层面通过饮食转换调整其植食或肉食的占比。我们提出如下假说：随着气温升高，外温性杂食动物的植食性占比将有所提升，该推论基于植食性随纬度向赤道方向递增的规律。我们依托外温性杂食动物分布广泛的淡水模式系统，采用温度操控实验与文献调研两种方法对该假说进行验证。我们针对稚龄水生外温性杂食动物——静水椎实螺（Lymnaea stagnalis）开展了温度区间为12℃至27℃的摄食实验，为其同时提供动物性饵料与植物性材料，并直接量化了……