Data from: Ant–caterpillar antagonism at the community level: interhabitat variation of tritrophic interactions in a neotropical savanna

1. Ant foraging on foliage can substantially affect how phytophagous insects use host plants and represents a high predation risk for caterpillars, which are important folivores. Ant–plant–herbivore interactions are especially pervasive in cerrado savanna due to continuous ant visitation to liquid food sources on foliage (extrafloral nectaries, insect honeydew). While searching for liquid rewards on plants, aggressive ants frequently attack or kill insect herbivores, decreasing their numbers. Because ants vary in diet and aggressiveness, their effect on herbivores also varies. Additionally, the differential occurrence of ant attractants (plant and insect exudates) on foliage produces variable levels of ant foraging within local floras and among localities. Here, we investigate how variation of ant communities and of traits among host plant species (presence or absence of ant attractants) can change the effect of carnivores (predatory ants) on herbivore communities (caterpillars) in a cerrado savanna landscape. We sampled caterpillars and foliage-foraging ants in four cerrado localities (70–460 km apart). We found that: (i) caterpillar infestation was negatively related with ant visitation to plants; (ii) this relationship depended on local ant abundance and species composition, and on local preference by ants for plants with liquid attractants; (iii) this was not related to local plant richness or plant size; (iv) the relationship between the presence of ant attractants and caterpillar abundance varied among sites from negative to neutral; and (v) caterpillars feeding on plants with ant attractants are more resistant to ant predation than those feeding on plants lacking attractants. Liquid food on foliage mediates host plant quality for lepidopterans by promoting generalized ant–caterpillar antagonism. Our study in cerrado shows that the negative effects of generalist predatory ants on herbivores are detectable at a community level, affecting patterns of abundance and host plant use by lepidopterans. The magnitude of ant-induced effects on caterpillar occurrence across the cerrado landscape may depend on how ants use plants locally and how they respond to liquid food on plants at different habitats. This study enhances the relevance of plant–ant and ant–herbivore interactions in cerrado and highlights the importance of a tritrophic perspective in this ant-rich environment.1. 蚂蚁在植物枝叶上觅食会显著影响植食性昆虫（phytophagous insects）对寄主植物的利用方式，同时对作为重要食叶动物的毛虫（caterpillars）构成极高的捕食风险。由于蚂蚁会持续访问植物枝叶上的液态食物来源——花外蜜腺（extrafloral nectaries）与昆虫蜜露（insect honeydew），蚁-植-植食者互作（ant–plant–herbivore interactions）在塞拉多稀树草原（cerrado savanna）中尤为普遍。在植物上搜寻液态奖赏时，具有攻击性的蚂蚁常会攻击或杀死昆虫植食者，从而降低其种群数量。 由于蚂蚁的食性与攻击性存在差异，其对植食者的调控效应也各不相同。此外，植物与昆虫分泌物这类蚂蚁引诱剂在枝叶上的分布差异，会导致本地植物区系内以及不同区域间蚂蚁觅食的强度存在波动。本研究旨在探究：在塞拉多稀树草原景观中，蚂蚁群落的变异以及寄主植物物种间的性状差异（是否存在蚂蚁引诱剂），会如何改变肉食性动物（捕食性蚂蚁）对植食者群落（毛虫）的调控效应。 我们在四个相隔70至460公里的塞拉多研究区域开展了毛虫与枝叶觅食蚂蚁的采样工作。研究结果显示：（i）毛虫侵染程度与蚂蚁对植物的访问量呈负相关关系；（ii）该相关关系取决于当地的蚂蚁丰度、物种组成，以及蚂蚁对带有液态引诱剂的植物的本地偏好性；（iii）该相关关系与当地植物丰富度或植株大小无关；（iv）蚂蚁引诱剂的存在与否与毛虫丰度之间的关联在不同样地间存在差异，从负相关转变为无相关性；（v）取食带有蚂蚁引诱剂的植物的毛虫，相较于取食无引诱剂植物的毛虫，对蚂蚁捕食的抵抗力更强。 枝叶上的液态食物通过促发广谱的蚁-毛虫拮抗作用，调控了鳞翅目昆虫（lepidopterans）的寄主植物质量。我们在塞拉多开展的研究表明：广食性捕食性蚂蚁对植食者的负面效应可在群落层面被检测到，并会影响鳞翅目昆虫的丰度模式与寄主植物利用方式。 在整个塞拉多景观中，蚂蚁诱导的毛虫种群变化效应的强弱，可能取决于蚂蚁在当地对植物的利用方式，以及它们对不同生境中植物上液态食物的响应情况。本研究强化了蚁-植互作与蚁-植食者互作在塞拉多生态系统中的重要性，并凸显了在这类蚂蚁多样性极高的环境中采用三重营养级视角（tritrophic perspective）开展研究的价值。