Département des Sciences Biologiques, Université du Québec à Montréal, Montréal, Quebec, H2X 1Y4, Canada.
Canada Research Chair in Integrative Ecology, Département de Biologie, Université de Sherbrooke, Sherbrooke, Quebec, J1K 2X9, Canada.
Ecology. 2019 Oct;100(10):e02815. doi: 10.1002/ecy.2815. Epub 2019 Aug 14.
The functional trait approach proposes that relating traits of organisms within a community to variation in abiotic and biotic characteristics of their environment will provide insight on the mechanisms of community assembly. As traits at a given trophic level might act as filters for the selection of traits at another trophic level, we hypothesized that traits of consumers and of their resources covary in space. We evaluated complementary predictions about top-down (negative) and bottom-up (positive) trait covariation in a detrital food web. Additionally, we tested whether positive trait covariation was better explained by the Resource Concentration Hypothesis (i.e., most commonly represented trait values attract abundant consumers) or the Resource Specialization Hypothesis (i.e., resource diversity increases niche availability for the consumers). Macroarthopods were collected with pitfall traps over two summers in three forested sites of southern Quebec in 110 plots that varied in tree species composition. Six feeding traits of consumers (detritivores and predators) and six palatability traits of their resources (leaf litter and prey) were matched to assess spatial covariation. Trait matches included consumer biting force/resource toughness, detritivore mandibular gape/leaf thickness, predator/prey body size ratio, etc. Our results demonstrate for the first time a covariation between feeding traits of detritivores and palatability traits of leaf litter (31-34%), and between feeding traits of litter-dwelling predators and palatability traits of potential prey (38-44%). The observed positive covariation supports both the Resource Concentration Hypothesis and Resource Specialization Hypothesis. Spatial covariation of consumer and resource traits provides a new tool to partially predict the structure of the detrital food web. Nonetheless, top-down regulation remains difficult to confirm. Further research on top-down processes will be undoubtedly necessary to refine our capacity to interpret the effect of biotic interactions on co-distribution.
功能性状方法提出，将群落内生物的性状与环境中生物和非生物特征的变化联系起来，将为群落组装的机制提供深入的了解。由于在给定的营养水平上的性状可能充当对另一营养水平上的性状选择的过滤器，我们假设消费者的性状与其资源在空间上是相关的。我们评估了碎屑食物网中自上而下（负）和自下而上（正）性状协同变化的补充预测。此外，我们还测试了正性状协同变化是否更能被资源集中假说（即，最常见的代表性状吸引丰富的消费者）或资源专业化假说（即，资源多样性增加了消费者的生态位可用性）来解释。在魁北克南部的三个森林地点的 110 个样地中，使用陷阱陷阱在两个夏季收集了宏观节肢动物，这些样地的树种组成不同。为了评估空间协同变化，我们将消费者（碎屑分解者和捕食者）的六个摄食性状和它们资源（落叶和猎物）的六个适口性性状进行了匹配。性状匹配包括消费者的咬合力/资源韧性、碎屑分解者的下颌间隙/叶厚度、捕食者/猎物的体型比等。我们的研究结果首次证明了碎屑分解者的摄食性状和落叶的适口性性状（31-34%）之间以及落叶栖息地的捕食者的摄食性状和潜在猎物的适口性性状（38-44%）之间存在协同变化。观察到的正协同变化支持资源集中假说和资源专业化假说。消费者和资源性状的空间协同变化为部分预测碎屑食物网的结构提供了新的工具。然而，自上而下的调节仍然难以证实。关于自上而下的过程的进一步研究无疑将有助于提高我们解释生物相互作用对共同分布的影响的能力。
