School of Biology, Faculty of Biological Sciences, University of Leeds, Leeds, UK.
Dynamic Ecology Group, Department of Biosciences, College of Science, Swansea University, Swansea, UK.
J Anim Ecol. 2019 Nov;88(11):1657-1669. doi: 10.1111/1365-2656.13069. Epub 2019 Aug 11.
Land-use and climate change are two of the primary drivers of the current biodiversity crisis. However, we lack understanding of how single-species and multispecies associations are affected by interactions between multiple environmental stressors. We address this gap by examining how environmental degradation interacts with daily stochastic temperature variation to affect individual life history and population dynamics in a host-parasitoid trophic interaction, using the Indian meal moth, Plodia interpunctella, and its parasitoid wasp Venturia canescens. We carried out a single-generation individual life-history experiment and a multigeneration microcosm experiment during which individuals and microcosms were maintained at a mean temperature of 26°C that was either kept constant or varied stochastically, at four levels of host resource degradation, in the presence or absence of parasitoids. At the individual level, resource degradation increased juvenile development time and decreased adult body size in both species. Parasitoids were more sensitive to temperature variation than their hosts, with a shorter juvenile stage duration than in constant temperatures and a longer adult life span in moderately degraded environments. Resource degradation also altered the host's response to temperature variation, leading to a longer juvenile development time at high resource degradation. At the population level, moderate resource degradation amplified the effects of temperature variation on host and parasitoid populations compared with no or high resource degradation and parasitoid overall abundance was lower in fluctuating temperatures. Top-down regulation by the parasitoid and bottom-up regulation driven by resource degradation contributed to more than 50% of host and parasitoid population responses to temperature variation. Our results demonstrate that environmental degradation can strongly affect how species in a trophic interaction respond to short-term temperature fluctuations through direct and indirect trait-mediated effects. These effects are driven by species differences in sensitivity to environmental conditions and modulate top-down (parasitism) and bottom-up (resource) regulation. This study highlights the need to account for differences in the sensitivity of species' traits to environmental stressors to understand how interacting species will respond to simultaneous anthropogenic changes.
土地利用和气候变化是当前生物多样性危机的两个主要驱动因素。然而，我们缺乏对单一物种和多物种之间的相互作用如何受到多种环境胁迫影响的理解。为了解决这一差距，我们研究了环境退化如何与日常随机温度变化相互作用，影响印度粉斑螟（Plodia interpunctella）及其寄生蜂谷斑螟绒茧蜂（Venturia canescens）在一个宿主-寄生性昆虫的营养相互作用中的个体生活史和种群动态。我们进行了一代个体生活史实验和多代微生境实验，在这两个实验中，个体和微生境在 26°C 的平均温度下保持不变或随机变化，有四个水平的宿主资源退化，有无寄生蜂。在个体水平上，资源退化增加了两种物种的幼期发育时间，减少了成虫体型。与宿主相比，寄生蜂对温度变化更为敏感，在恒温下幼期持续时间较短，在中度退化环境下成虫寿命较长。资源退化还改变了宿主对温度变化的反应，导致在高资源退化时幼期发育时间延长。在种群水平上，与没有或高度资源退化相比，中度资源退化放大了温度变化对宿主和寄生蜂种群的影响，并且在波动温度下寄生蜂的总体丰度较低。寄生蜂的自上而下的调节和资源退化驱动的自下而上的调节对宿主和寄生蜂种群对温度变化的反应贡献了超过 50%。我们的研究结果表明，环境退化可以通过直接和间接的性状介导效应强烈影响营养相互作用中的物种对短期温度波动的反应。这些效应是由物种对环境条件的敏感性差异驱动的，并调节了自上而下（寄生）和自下而上（资源）的调节。本研究强调需要考虑物种特征对环境胁迫的敏感性差异，以了解相互作用的物种如何对同时发生的人为变化做出反应。
