Ant Resource Detection Distance at the Caxiuana National Forest in Brazil 2017-2018

Environmental change scenarios of low precipitation forecast species loss in tropical regions. These losses can affect generalist species that provide important ecosystem services, such as controlling the rate at which nutrients become available for uptake by other organisms in tropical forests. Here, we use a long-term rainwater exclusion experiment in primary Amazonian rainforest to test whether induced water stress affects the detection distance of food resources (baits) in a generalist ant guild (number of colonies, richness, and composition) that remove resources on the ground. We found that (i) overall the distance of resource removal by generalist ants did not change with drought; (ii) however, comparing ant species that occurred in drought-induced and control environments, workers walked shorter distances in the drought habitat; (iii) the number of resources detected by ant colonies in the drought-induced habitat decreased by 50%. Although generalist ants are considered resilient to habitat disturbance, the effect of reduced rainfall can negatively affect the services mediated by them. The rate of removal and consumption of resources in tropical forests may be related to abundance of generalist ants; losses in both nest density and walking distances may cause cascading effects on ecosystem processes and the services they mediate.

热带地区低降水环境变化情景下的物种丧失预测。此类物种丧失会波及提供重要生态系统服务（ecosystem services）的广适性物种，例如调控热带森林中养分可供其他生物吸收利用速率的类群。为此，我们依托亚马逊原生雨林（primary Amazonian rainforest）中的长期雨水排除实验（long-term rainwater exclusion experiment），针对在地面移除资源的广谱蚁类群（generalist ant guild，考察指标包括蚁群数量、物种丰富度与物种组成），检验诱导产生的水分胁迫（water stress）是否会影响其对食物资源（诱饵）的探测距离。我们得到如下结果：（i）总体而言，广谱蚁类移除资源的距离未随干旱发生变化；（ii）然而对比干旱诱导生境（drought-induced habitat）与对照生境中的蚁类物种，工蚁在干旱生境中的行走距离更短；（iii）干旱生境中蚁群探测到的资源数量下降了50%。尽管广谱蚁类被认为对栖息地干扰具备耐受性，但降水减少的影响仍会对其介导的生态系统服务产生负面影响。热带森林中的资源移除与消耗速率或与广谱蚁类的丰度相关；蚁巢密度（nest density）与行走距离的双重损失，可能会对生态系统过程及其介导的服务产生级联效应（cascading effects）。