Post David M, Palkovacs Eric P, Schielke Erika G, Dodson Stanley I
Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut 06520-8106, USA.
Ecology. 2008 Jul;89(7):2019-32. doi: 10.1890/07-1216.1.
Intraspecific phenotypic variation in ecologically important traits is widespread and important for evolutionary processes, but its effects on community and ecosystem processes are poorly understood. We use life history differences among populations of alewives, Alosa pseudoharengus, to test the effects of intraspecific phenotypic variation in a predator on pelagic zooplankton community structure and the strength of cascading trophic interactions. We focus on the effects of differences in (1) the duration of residence in fresh water (either seasonal or year-round) and (2) differences in foraging morphology, both of which may strongly influence interactions between alewives and their prey. We measured zooplankton community structure, algal biomass, and spring total phosphorus in lakes that contained landlocked, anadromous, or no alewives. Both the duration of residence and the intraspecific variation in foraging morphology strongly influenced zooplankton community structure. Lakes with landlocked alewives had small-bodied zooplankton year-round, and lakes with no alewives had large-bodied zooplankton year-round. In contrast, zooplankton communities in lakes with anadromous alewives cycled between large-bodied zooplankton in the winter and spring and small-bodied zooplankton in the summer. In summer, differences in feeding morphology of alewives caused zooplankton biomass to be lower and body size to be smaller in lakes with anadromous alewives than in lakes with landlocked alewives. Furthermore, intraspecific variation altered the strength of the trophic cascade caused by alewives. Our results demonstrate that intraspecific phenotypic variation of predators can regulate community structure and ecosystem processes by modifying the form and strength of complex trophic interactions.
生态重要性状的种内表型变异广泛存在，对进化过程至关重要，但其对群落和生态系统过程的影响却知之甚少。我们利用美洲西鲱（Alosa pseudoharengus）种群间的生活史差异，来测试捕食者的种内表型变异对浮游动物群落结构以及级联营养相互作用强度的影响。我们重点关注以下差异的影响：（1）在淡水中停留的时间（季节性或全年），以及（2）觅食形态的差异，这两者都可能强烈影响美洲西鲱与其猎物之间的相互作用。我们测量了包含内陆型、溯河洄游型或没有美洲西鲱的湖泊中的浮游动物群落结构、藻类生物量和春季总磷含量。停留时间和觅食形态的种内变异都强烈影响了浮游动物群落结构。有内陆型美洲西鲱的湖泊全年都有小型浮游动物，而没有美洲西鲱的湖泊全年都有大型浮游动物。相比之下，有溯河洄游型美洲西鲱的湖泊中的浮游动物群落则在冬季和春季为大型浮游动物，夏季为小型浮游动物之间循环。在夏季，溯河洄游型美洲西鲱的湖泊中，美洲西鲱觅食形态的差异导致浮游动物生物量低于有内陆型美洲西鲱的湖泊，且体型更小。此外，种内变异改变了由美洲西鲱引起的营养级联强度。我们的结果表明，捕食者的种内表型变异可以通过改变复杂营养相互作用的形式和强度来调节群落结构和生态系统过程。
