Data from: Consumer trait variation influences tri-trophic interactions in salt marsh communities

The importance of intraspecific variation has emerged as a key question in community ecology, helping to bridge the gap between ecology and evolution. Although much of this work has focused on plant species, recent syntheses have highlighted the prevalence and potential importance of morphological, behavioral, and life history variation within animals for ecological and evolutionary processes. Many small-bodied consumers live on the plant that they consume, often resulting in host plant-associated trait variation within and across consumer species. Given the central position of consumer species within tritrophic food webs, such consumer trait variation may play a particularly important role in mediating trophic dynamics, including trophic cascades. In this study, we used a series of field surveys and laboratory experiments to document intraspecific trait variation in a key consumer species, the marsh periwinkle Littoraria irrorata, based on its host plant species (Spartina alterniflora or Juncus roemerianus) in a mixed species assemblage. We then conducted a 12-week mesocosm experiment to examine the effects of Littoraria trait variation on plant community structure and dynamics in a tritrophic salt marsh food web. Littoraria from different host plant species varied across a suite of morphological and behavioral traits. These consumer trait differences interacted with plant community composition and predator presence to affect overall plant stem height, as well as differentially alter the density and biomass of the two key plant species in this system. Whether due to genetic differences or phenotypic plasticity, trait differences between consumer types had significant ecological consequences for the tritrophic marsh food web over seasonal time scales. By altering the cascading effects of the top predator on plant community structure and dynamics, consumer differences may generate a feedback over longer time scales, which in turn influences the degree of trait divergence in subsequent consumer populations.

种内变异（intraspecific variation）的重要性已成为群落生态学的核心议题，有助于弥合生态学与进化生物学之间的研究鸿沟。尽管此类研究多聚焦于植物物种，但近期综合研究凸显了动物种群内的形态、行为及生活史变异在生态与进化过程中的普遍性与潜在重要性。许多小型消费者栖息于其所取食的植物之上，这往往导致消费者物种内部及跨物种间出现与宿主植物相关的性状变异。鉴于消费者物种在三层营养级食物网（tritrophic food webs）中的核心地位，此类消费者性状变异可能在介导营养动态（trophic dynamics），包括营养级联效应（trophic cascades）中发挥尤为关键的作用。本研究通过一系列野外调查与室内实验，以混合物种群落中的宿主植物物种——互花米草（Spartina alterniflora）或罗默灯心草（Juncus roemerianus）——为依托，对关键消费者物种潮间带滨螺（Littoraria irrorata）的种内性状变异进行了记录。随后我们开展了为期12周的中型实验生态系统（mesocosm）实验，以探究滨螺性状变异对三层营养级盐沼食物网中植物群落结构与动态的影响。来自不同宿主植物的滨螺在一系列形态与行为性状上均存在显著差异。这些消费者性状差异与植物群落组成及捕食者存在与否相互作用，共同影响植物的整体茎高，并对该系统中两种关键植物物种的密度与生物量产生差异化调控效应。无论消费者类群间的性状差异源于遗传分化还是表型可塑性（phenotypic plasticity），其均会在季节尺度上对三层营养级盐沼食物网产生显著的生态效应。通过改变顶级捕食者对植物群落结构与动态的级联效应，消费者性状差异可能在更长时间尺度上产生反馈调控，进而影响后续消费者种群的性状分化程度。