Laws Angela N, Joern Anthony
Division of Biology, Kansas State University, Manhattan, KS 66506, USA.
Division of Biology, Kansas State University, Manhattan, KS 66506, USA.Present address: Department of Biology, University of Notre Dame, Notre Dame, IN, USA.
Environ Entomol. 2015 Jun;44(3):519-28. doi: 10.1093/ee/nvv033. Epub 2015 Mar 29.
Species interactions are often context dependent, where outcomes vary in response to one or more environmental factors. It remains unclear how abiotic conditions like temperature combine with biotic factors such as consumer density or food quality to affect resource availability or influence species interactions. Using the large grasshopper Melanoplus bivittatus (Say) and a common wolf spider [Rabidosa rabida (Walkenaer)], we conducted manipulative field experiments in tallgrass prairie to examine how spider-grasshopper interactions respond to manipulations of temperature, grasshopper density, and food quality. Grasshopper survival was density dependent, as were the effects of spider presence and food quality in context-dependent ways. In high grasshopper density treatments, predation resulted in increased grasshopper survival, likely as a result of reduced intraspecific competition in the presence of spiders. Spiders had no effect on grasshopper survival when grasshoppers were stocked at low densities. Effects of the experimental treatments were often interdependent so that effects were only observed when examined together with other treatments. The occurrence of trophic cascades was context dependent, where the effects of food quality and spider presence varied with temperature under high-density treatments. Temperature weakly affected the impact of spider presence on M. bivittatus survivorship when all treatments were considered simultaneously, but different context-dependent responses to spider presence and food quality were observed among the three temperature treatments under high-density conditions. Our results indicate that context-dependent species interactions are common and highlight the importance of understanding how key biotic and abiotic factors combine to influence species interactions.
物种间的相互作用通常取决于环境背景，其结果会随着一个或多个环境因素的变化而改变。目前尚不清楚诸如温度等非生物条件如何与消费者密度或食物质量等生物因素相结合，从而影响资源可用性或影响物种间的相互作用。我们以大型蚱蜢双线黑蝗（Melanoplus bivittatus (Say)）和一种常见的狼蛛（狂蛛Rabidosa rabida (Walkenaer)）为研究对象，在高草草原进行了控制性田间实验，以探究蜘蛛与蚱蜢之间的相互作用如何响应温度、蚱蜢密度和食物质量的变化。蚱蜢的存活率取决于密度，蜘蛛的存在和食物质量的影响也因环境背景而异。在高蚱蜢密度处理中，捕食导致蚱蜢存活率增加，这可能是由于蜘蛛存在时种内竞争减少所致。当蚱蜢低密度放养时，蜘蛛对蚱蜢存活率没有影响。实验处理的效果通常是相互依存的，因此只有在与其他处理一起考虑时才能观察到效果。营养级联的发生取决于环境背景，在高密度处理下，食物质量和蜘蛛存在的影响会随温度而变化。当同时考虑所有处理时温度对蜘蛛存在对双线黑蝗存活率的影响较弱，但在高密度条件下的三种温度处理中，观察到对蜘蛛存在和食物质量的不同环境背景依赖性反应。我们的结果表明，环境背景依赖性的物种间相互作用很常见，并强调了理解关键生物和非生物因素如何结合以影响物种间相互作用的重要性。
