Kenna Daniel, Fincham William N W, Dunn Alison M, Brown Lee E, Hassall Christopher
School of Biology and water@leeds, University of Leeds, Leeds, UK.
School of Geography and water@leeds, University of Leeds, Leeds, UK.
Oecologia. 2017 Mar;183(3):875-886. doi: 10.1007/s00442-016-3796-x. Epub 2016 Dec 24.
Global biodiversity is threatened by multiple anthropogenic stressors but little is known about the combined effects of environmental warming and invasive species on ecosystem functioning. We quantified thermal preferences and then compared leaf-litter processing rates at eight different temperatures (5.0-22.5 °C) by the invasive freshwater crustacean Dikerogammarus villosus and the Great Britain native Gammarus pulex at a range of body sizes. D. villosus preferred warmer temperatures but there was considerable overlap in the range of temperatures that the two species occupied during preference trials. When matched for size, G. pulex had a greater leaf shredding efficiency than D. villosus, suggesting that invasion and subsequent displacement of the native amphipod will result in reduced ecosystem functioning. However, D. villosus is an inherently larger species and interspecific variation in shredding was reduced when animals of a representative size range were compared. D. villosus shredding rates increased at a faster rate than G. pulex with increasing temperature suggesting that climate change may offset some of the reduction in function. D. villosus, but not G. pulex, showed evidence of an ability to select those temperatures at which its shredding rate was maximised, and the activation energy for shredding in D. villosus was more similar to predictions from metabolic theory. While per capita and mass-corrected shredding rates were lower in the invasive D. villosus than the native G. pulex, our study provides novel insights in to how the interactive effects of metabolic function, body size, behavioural thermoregulation, and density produce antagonistic effects between anthropogenic stressors.
全球生物多样性受到多种人为压力源的威胁，但对于环境变暖和入侵物种对生态系统功能的综合影响却知之甚少。我们量化了热偏好，然后比较了入侵性淡水甲壳动物绒毛小采（Dikerogammarus villosus）和英国本土的蚤状钩虾（Gammarus pulex）在一系列体型下，于八个不同温度（5.0 - 22.5°C）下的落叶处理速率。绒毛小采偏好更温暖的温度，但在偏好试验中，这两个物种所占据的温度范围有相当大的重叠。当体型相匹配时，蚤状钩虾的叶片切碎效率高于绒毛小采，这表明本地双足虾的入侵及随后的被取代将导致生态系统功能下降。然而，绒毛小采本身就是体型较大的物种，当比较具有代表性体型范围的动物时，切碎过程中的种间差异减小了。随着温度升高，绒毛小采的切碎速率比蚤状钩虾增加得更快，这表明气候变化可能抵消部分功能下降。绒毛小采（而非蚤状钩虾）表现出能够选择使其切碎速率最大化的温度的能力，并且绒毛小采切碎过程的活化能更类似于代谢理论的预测。虽然入侵的绒毛小采的人均和质量校正切碎速率低于本土的蚤状钩虾，但我们的研究为代谢功能、体型、行为体温调节和密度的交互作用如何在人为压力源之间产生拮抗效应提供了新的见解。
