Trophic interactions and ecological functions of ants under changing tree diversity

更广泛的研究背景：植物多样性与营养水平上的消费者多样性有关，但很少有研究调查森林中生产者（即树木）多样性如何影响多营养相互作用和节肢动物的生态系统功能。揭示树木多样性和营养相互作用之间的关系对于理解生物多样性-生态系统功能之间的关系至关重要，这通常是涉及节肢动物的相互作用的结果。发生在几个营养水平，从植食性到高度掠食性，大多数物种是杂食动物，蚂蚁是研究多营养相互作用的理想选择。假设：根据初步结果，我们假设蚂蚁物种多样性随着树木多样性的增加而增加。根据“敌人假说”，我们假设蚂蚁捕食生活方式的程度随着树木多样性的增加而增加，并且功能形态空间向相对更捕食的群落转移。此外，当树的多样性和蚂蚁的多样性较高时，我们期望资源选择具有更高的通用性和冗余性。这些树木多样性介导的营养相互作用变化与已实现的营养生态位有关，物种水平δ15N越高，表明动物源性食物的份额越大，群落同位素生态位宽度越宽，表明营养冗余。我们假设“清除”功能随着树木多样性的增加而增加，这与蚂蚁多样性和性状分布以及营养位置有关，这些都是由树木多样性介导的。方法：在所有的核心样地，我们将量化蚂蚁多样性和性状分布，以功能表征所有收集到的物种。为了确定单个物种和整个蚂蚁群落的营养位置，量化营养生态位宽度和营养冗余，我们将进行资源选择实验和δ15N同位素值测量。我们还将测试哪些性状与营养生态位宽度和相对营养位置有关。为了将蚂蚁多样性和营养相互作用与生态系统功能联系起来，我们将测量“清除”作为VIP样地标准腐肉诱饵的检索率。创新：除了我们最初的工作外，蚂蚁很少在树木多样性实验中被研究过。通过整合一个关键节肢动物分类单元的生物组织组成，我们将揭示树木多样性、蚂蚁多样性、性状分布和营养相互作用之间的相互作用如何影响森林生态系统功能。我们的数据将允许预测蚂蚁多样性是否在简化的生态系统中减少，以及蚂蚁介导的功能如何依赖于多样性和跨营养水平的相互作用。主要研究人员：该项目将由Michael Staab（达姆施塔特PI）和Heike Feldhaar（拜罗伊特Co-PI）与我们的中国合作伙伴xiajuan Liu（北京）合作进行。

Wider research context: Plant diversity relates to consumer diversity across trophic levels, but only few studies investigated in forests how producer (i.e. tree) diversity influences multitrophic interactions and ecosystem functions of arthropods. Unravelling the relationship between tree diversity and trophic interactions is crucial to understand biodiversity-ecosystem functioning relationships, which are often the outcome of interactions involving arthropods. Occurring in several trophic levels, from phytophagous to highly predacious, with most species being omnivores, ants are ideal for studying multitrophic interactions.Hypotheses: In line with preliminary results, we hypothesize that ant species diversity increases with tree diversity. Following the enemies hypothesis, we hypothesize that the degree of ant predatory life style increases with tree diversity and that functional morphospace shifts towards relatively more predacious communities. Alongside, we expect higher generality and redundancy in resource choice when tree diversity and, thus, ant diversity is high. These tree diversity-mediated changes in trophic interactions relate to realized trophic niches, with higher species-level δ15N indicating a larger share of animal-derived food objects and with broader community isotopic niche breadth indicating trophic redundancy. We hypothesise that the function ‘scavenging’ increases with tree diversity, which is mechanistically related to ant diversity and trait distribution as well as trophic positions, that are all mediated by tree diversity.Methods: In all core plots, we will quantify ant diversity and trait distribution to functionally characterise all collected species. To identify the trophic position of individual species and the entire ant community and to quantify trophic niche breadth and trophic redundancy, we will perform resource-choice experiments and measure δ15N isotope values. We will also test which traits relate to trophic niche breadth and relative trophic position. To link ant diversity and trophic interactions to an ecosystem function, we will measure ‘scavenging’ as the retrieval rate of standard carrion baits in the VIP plots.Innovation: Ants have, with the exception of our initial work, only rarely been studied in tree diversity experiments. By integrating across components of biological organization in a key arthropod taxon we will reveal how the interplay among tree diversity, ant diversity, trait distribution and trophic interactions influences forest ecosystem functionality. Our data will allow predicting if ant diversity decreases in simplified ecosystems and how ant-mediated functions depend on diversity and interactions across trophic levels.Primary researchers involved: This project will be conducted by Michael Staab (PI, Darmstadt) and Heike Feldhaar (Co-PI, Bayreuth), in collaboration with our Chinese partner Xiaojuan Liu (Beijing).