Oklahoma Biological Survey and Department of Zoology, University of Oklahoma, Norman, OK 73019, USA.
Oecologia. 2012 Feb;168(2):533-48. doi: 10.1007/s00442-011-2110-1. Epub 2011 Sep 8.
Changing environments can have divergent effects on biodiversity-ecosystem function relationships at alternating trophic levels. Freshwater mussels fertilize stream foodwebs through nutrient excretion, and mussel species-specific excretion rates depend on environmental conditions. We asked how differences in mussel diversity in varying environments influence the dynamics between primary producers and consumers. We conducted field experiments manipulating mussel richness under summer (low flow, high temperature) and fall (moderate flow and temperature) conditions, measured nutrient limitation, algal biomass and grazing chironomid abundance, and analyzed the data with non-transgressive overyielding and tripartite biodiversity partitioning analyses. Algal biomass and chironomid abundance were best explained by trait-independent complementarity among mussel species, but the relationship between biodiversity effects across trophic levels (algae and grazers) depended on seasonal differences in mussel species' trait expression (nutrient excretion and activity level). Both species identity and overall diversity effects were related to the magnitude of nutrient limitation. Our results demonstrate that biodiversity of a resource-provisioning (nutrients and habitat) group of species influences foodweb dynamics and that understanding species traits and environmental context are important for interpreting biodiversity experiments.
改变环境会对不同营养级的生物多样性-生态系统功能关系产生不同的影响。淡水贻贝通过排泄营养物质来为溪流食物网提供养分，而贻贝物种特异性的排泄率取决于环境条件。我们想知道在不同环境中贻贝多样性的差异如何影响初级生产者和消费者之间的动态关系。我们在夏季（低流量、高温）和秋季（中等流量和温度）条件下进行了现场实验，操纵贻贝丰度，测量营养限制、藻类生物量和食藻类摇蚊的丰度，并使用非转移超产量和三分体生物多样性分配分析来分析数据。藻类生物量和食藻类摇蚊的丰度最好用贻贝物种之间独立于特征的互补性来解释，但跨营养级（藻类和食草动物）的生物多样性效应之间的关系取决于贻贝物种特征表达（营养排泄和活动水平）的季节性差异。物种身份和总体多样性效应都与营养限制的程度有关。我们的结果表明，提供资源（营养物质和栖息地）的物种的生物多样性会影响食物网的动态，而理解物种特征和环境背景对于解释生物多样性实验非常重要。
