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

蚂蚁是温带草原重要的生态系统工程师，因为它们通过建造地下巢穴并将资源输入这些巢穴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对蚂蚁群落的结构产生负面影响，减少蚂蚁物种的丰富度和丰度，从而对它们作为土壤工程师的功能产生潜在影响。然而，导致社区结构变化的机制并不十分清楚。不同类型的土地利用可能会影响蚂蚁群落的组成和整体蚂蚁丰度，要么通过改变现有的食物来源（间接影响）或通过干扰筑巢地点（直接影响）。草原上的蚂蚁群落通常包括消耗猎物，昆虫或通过营养共生（例如蚜虫）以植物来源的食物来源为食的物种，或依赖于这些食物来源中的几种。集约化的土地利用通常会导致较低的植物物种丰富度，这与更频繁的割草可能会导致较低的滋养生物丰富度以上以及地下，而潜在的猎物项目（如generalisitc草食动物）可能会受到较少的影响。因此，杂食性蚂蚁物种可能会表现出相对更多的捕食的营养生态位的转变。如果这种营养可塑性是有限的，社区可能包括一个不同的物种，并显示出转向更捕食性的物种。这两种机制导致蚂蚁群落在更高的营养水平上进食。蚂蚁也应该直接受到更密集的土地使用的影响，因为割草和大量放牧会干扰筑巢地点。筑堤物种应该比其他物种受到更强烈的干扰。蚂蚁以及滋养生物物种的丰富度和丰度将被测量以上和地下的所有草原地块和记录群体之间的相互作用。蚂蚁的营养生态位将使用稳定同位素分析以及在该领域的首选营养摄入量进行评估。群落组装的机制将结合共生模式与系统发育和表型数据进行分析。蚂蚁和蚜虫之间的营养相互作用的特异性的潜在变化将使用网络分析进行评估。

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.