Data from: Species-level predation network uncovers high prey specificity in a Neotropical army ant community

Army ants are among the top arthropod predators and considered keystone species in tropical ecosystems. During daily mass raids with many thousand workers, army ants hunt live prey, likely exerting strong top-down control on prey species. Many tropical sites exhibit a high army ant species diversity (>20 species), suggesting that sympatric species partition the available prey niches. However, whether and to what extent this is achieved has not been intensively studied yet. We therefore conducted a large-scale diet survey of a community of surface-raiding army ants at La Selva Biological Station in Costa Rica. We systematically collected 3,262 prey items from eleven army ant species (genera Eciton, Nomamyrmex and Neivamyrmex). Prey items were classified as ant prey or non-ant prey. The prey nearly exclusively consisted of other ants (98%), and most booty was ant brood (87%). Using morphological characters and DNA barcoding, we identified a total of 1,105 ant prey specimens to the species level. 129 ant species were detected among the army ant prey, representing about 30% of the known local ant diversity. Using weighted bipartite network analyses, we show that prey specialization in army ants is unexpectedly high, and prey niche overlap very small. Besides food niche differentiation, we uncovered a spatio-temporal niche differentiation in army ant raid activity. We discuss competition-driven multidimensional niche differentiation and predator-prey arms races as possible mechanisms underlying prey specialization in army ants. By combining systematic prey sampling with species-level prey identification and network analyses, our integrative approach can guide future research by portraying how predator-prey interactions in complex communities can be reliably studied, even in cases where morphological prey identification is infeasible.

行军蚁（Army ants）是顶级节肢动物捕食者之一，被视作热带生态系统中的关键物种（keystone species）。在每日由数千只工蚁参与的集群突袭行动中，行军蚁捕猎活体猎物，大概率对猎物种群施加了强烈的下行控制（top-down control）。诸多热带区域拥有极高的行军蚁物种多样性（>20种），这提示同域分布物种（sympatric species）会对可利用的猎物生态位进行分区利用。然而，此类生态位分区利用是否存在、以及其实现程度如何，迄今尚未得到深入研究。为此，我们在哥斯达黎加拉塞尔瓦生物站（La Selva Biological Station）针对地表活动的行军蚁群落开展了大规模食性调查。我们从隶属于行军蚁属（Eciton）、裸足行军蚁属（Nomamyrmex）和迷走行军蚁属（Neivamyrmex）的11种行军蚁中，系统采集了3262份猎物样本。猎物样本被划分为蚁类猎物与非蚁类猎物两类。本次研究的猎获物几乎全部为其他蚂蚁（占比98%），其中绝大多数为蚁类幼体（ant brood，占比87%）。借助形态学特征与DNA条形码（DNA barcoding）技术，我们共将1105份蚁类猎物样本鉴定至物种水平。在行军蚁的猎获物中，共检测到129种蚂蚁，约占当地已知蚂蚁物种多样性的30%。通过加权二分网络分析（weighted bipartite network analyses），我们发现行军蚁的猎物特化程度出乎意料地高，且猎物生态位重叠度极低。除食物生态位分化外，我们还揭示了行军蚁突袭活动的时空生态位分化（spatio-temporal niche differentiation）。我们讨论了竞争驱动的多维生态位分化与捕食者-猎物军备竞赛（predator-prey arms races）作为行军蚁猎物特化背后的潜在机制。通过将系统性猎物采样、物种级猎物鉴定与网络分析相结合，我们的整合研究方法（integrative approach）可为未来研究提供指引：即便在无法通过形态学完成猎物鉴定的场景下，如何可靠地解析复杂群落中的捕食者-猎物相互作用。