Data from: Human disturbance promotes herbivory by leaf-cutting ants in the Caatinga dry forest

Anthropogenic disturbances are known to modify plant-animal interactions such as those involving the leaf-cutting ants, the most voracious and proliferating herbivore across human-modified landscapes in the Neotropics. Here we evaluate the effect of chronic anthropogenic disturbance (e.g. firewood collection, livestock grazing) and vegetation seasonality on foraging area, foliage availability in the foraging area, leaf consumption, and herbivory rate of the leaf-cutting ant Atta opaciceps in the semi-arid Caatinga, a mosaic of dry forest and scrub vegetation in northeast Brazil. Contrary to our initial expectation, the foraging area was not affected by either disturbance intensity or the interaction between season and disturbance intensity. However, leaf consumption and herbivory rate were higher in more disturbed areas. We also found a strong effect of seasonality, with higher leaf consumption and herbivory rate in the dry season. Our results suggest that the foraging ecology of leaf-cutting ants is modulated by human disturbance and seasonality as these two drivers affect the spectrum and the amount of resources available for these ants in the Caatinga. Despite the low productivity of Caatinga vegetation, the annual rates of biomass consumption by A. opaciceps are similar to those reported from other leaf-cutting ants in rainforests and savannas. This is made possible by maintaining high foraging activity even in the peak of the dry season and taking benefit from any resource available, including low-quality items. Such compensation highlights the adaptive capacity of LCA to persist or even proliferate in human-modified landscapes from dry to rainforests.已有研究表明，人为干扰（anthropogenic disturbances）会改变动植物间的相互作用，其中便包括切叶蚁（leaf-cutting ants）——它们是新热带区受人类活动改造景观中食量最大、繁殖最快的植食类群。本研究在巴西东北部半干旱的卡廷加（Caatinga，一种由旱林与灌丛构成的镶嵌植被群落）生境中，探究了长期人为干扰（如薪柴采集、家畜放牧）与植被季节性变化对切叶蚁Atta opaciceps的觅食范围、觅食区内叶片可获得性、叶片消耗量与植食率的影响。与我们的初始预期相悖，觅食范围既未受干扰强度的单独影响，也未受季节与干扰强度的交互作用影响。但在干扰程度更高的区域，叶片消耗量与植食率均显著升高。此外，我们还发现植被季节性变化存在显著影响：旱季的叶片消耗量与植食率均更高。本研究结果表明，切叶蚁的觅食生态会受人为干扰与季节性变化共同调控——这两类驱动因子会影响卡廷加生境中可供切叶蚁利用的资源种类与资源总量。尽管卡廷加植被的生产力较低，但Atta opaciceps的年生物量消耗量与热带雨林、热带稀树草原中其他切叶蚁物种的报道值相近。这一现象的成因在于：即便在旱季峰值时段，该切叶蚁仍能维持高强度的觅食活动，且可利用一切可获取的资源（包括低质量的食物资源）。这种补偿机制彰显了切叶蚁（leaf-cutting ants，简称LCA）的适应能力，使其能够在从干旱生境至热带雨林的各类受人类活动改造的景观中存续甚至繁衍。