Direct and indirect effects of land use intensification on ant communities in temperate grasslands

蚂蚁是温带草原上重要的生态系统工程师，因为它们通过建造地下巢穴和向这些巢穴输入资源来改变土壤结构和微生物群落。土地利用的集约化已被证明会减少蚂蚁物种的丰富度和丰富度，从而对蚂蚁群落的结构产生负面影响，这可能会对它们作为土壤工程师的功能产生影响。然而，导致社区结构变化的机制还不是很清楚。不同类型的土地利用可能通过改变可用的食物来源(间接影响)或通过干扰筑巢地点(直接影响)影响蚂蚁群落的组成和蚂蚁的总体丰度。草原上的蚂蚁群落通常包括通过营养生物(例如，蚜虫)捕食、觅食或以植物来源的食物来源为食的物种，或依赖于其中几种食物来源的物种。土地利用的加强通常会导致植物物种丰富度降低，再加上更频繁的修剪，可能会导致地上和地下的营养生物丰富度降低，而潜在的猎物(如一般食草动物)可能受到的影响较小。因此，杂食性蚂蚁物种可能会表现出营养生态位向相对更多的捕食转变。如果这种营养可塑性是有限的，群落可能包括一组不同的物种，并显示出向更具捕食性的物种转变。这两种机制都会导致蚂蚁群落在更高的营养水平上觅食。蚂蚁还应该受到更集约的土地利用的直接影响，因为割草和大量放牧干扰了筑巢地点。与其他物种相比，土堆建造物种受干扰的影响更大。将在所有草原地块上和地下测量蚂蚁和营养层物种的丰富度和丰富度，以及记录的群体之间的相互作用。蚂蚁的营养生态位将使用稳定的同位素分析以及田间首选的营养摄入量进行评估。通过将共生模式与系统发育和表型数据相结合，将分析群落聚集的机制。将使用网络分析来评估蚂蚁和蚜虫之间营养相互作用的特异性的潜在变化。

Ants are important ecosystem engineers in temperate grasslands as they modify soil structure and microbial communities by building subterranean nests and importing resources into these nests. Intensification of land use has been shown to negatively influence the structure of ant communities by reducing ant species richness and abundance with potential consequences for their functions as soil engineers. However, the mechanisms leading to changes in community structure are not well understood. Different types of land use may affect composition of ant communities and overall ant abundance either by altering available food sources (indirect effects) or by disturbance of nesting sites (direct effects). Ant communities in grasslands usually comprise species that consume prey, scavenge or feed on plant-derived food sources via trophobiosis (e.g. with aphids ), or rely on several of these food sources. Intensified land use typically results in lower plant species richness, which in concert with more frequent mowing may result in lower trophobiont abundance above as well as below-ground, while potential prey items (e.g. generalisitc herbivores) may be less affected. Omnivorous ant species may therefore show a shift in trophic niche towards relatively more predation. If such trophic plasticity is limited, the community may comprise a different set of species and show a shift towards more predacious species. Both mechanisms result in an ant community feeding on a higher trophic level. Ants should also be affected directly by more intensive land use due to disturbance of nesting sites by mowing and heavy grazing. Mound-building species should be more strongly affected by disturbances than other species. Ant as well as trophobiont species richness and abundance will be measured above and belowground on all grassland plots and interactions among the groups documented. The trophic niche of ants will be assessed using stable isotope analyses as well as preferred nutrient intake in the field. Mechanisms of community assembly will be analyzed by combining co-occurrence patterns with phylogenetic and phenotypic data. Potential changes in the specificity of trophic interactions between ants and aphids will be assessed using network analyses.