Data from: The influence of host plant extrafloral nectaries on multitrophic interactions: an experimental investigation

A field experiment was conducted with outplantings of the native perennial shrub Senna mexicana var. chapmanii in a semi-natural area adjacent to native pine rockland habitat in southern Florida. The presence of ants and the availability of extrafloral nectar were manipulated in a stratified random design. Insect communities were monitored and recorded over a period of six months with a view to addressing three main questions. Do ants provide biotic defense against key herbivores on S. chapmanii? Is the presence of ants on S. chapmanii mediated by EFN? Finally, are there ecological costs associated with the presence of ants on S. chapmanii, such as a reduction in alternative predator or parasitoid numbers? Herbivores on S. chapmanii included immature stages of three pierid butterflies, and adult weevils. Eight species of ants were associated with the plants, and other predators included spiders, ladybugs, wasps, and hemipterans. Parasitic, haemolymph-sucking midges (Ceratopogonidae) and parasitoid flies were also associated with the caterpillar herbivores, and possibly the extrafloral nectaries of the plants. The presence of ants did not appear to influence oviposition by butterflies, as numbers of lepidopterans of all developmental stages did not differ among treatments. Significantly more late instar caterpillars, however, were observed on plants with ants excluded, indicating that ants remove small caterpillars from plants. Substantially more alternative predators (spiders, ladybugs, and wasps) were observed on plants with ants excluded. Rates of parasitization did not differ among the treatments, but there were substantially fewer caterpillars succumbing to virus among those collected from control plants. We provide a rare look at facultative ant-plant mutualisms in the context of the many other interactions with which they overlap. We conclude that ants provide some biotic defense against herbivores on S. chapmanii, and plants benefit overall from the presence of ants, despite negative impacts on non-ant predators.

本研究于美国佛罗里达州南部毗邻本土松岩生境的半自然区域开展田间试验，以本土多年生灌木墨西哥番泻查普曼变种（Senna mexicana var. chapmanii）的定植植株为研究对象。采用分层随机设计人为调控蚂蚁的存在与花外蜜（extrafloral nectar）的可获得性。在为期6个月的监测周期内对昆虫群落进行监测并记录，旨在探讨三个核心科学问题：其一，蚂蚁能否为S. chapmanii上的主要植食性昆虫提供生物防御？其二，S. chapmanii上的蚂蚁定殖是否由花外蜜腺（extrafloral nectaries）介导？其三，S. chapmanii上的蚂蚁定殖是否会带来生态成本，例如降低其他捕食性或寄生性天敌的种群数量？S. chapmanii上的植食性昆虫包括3种粉蝶科蝴蝶的幼态阶段与成虫象甲。共记录到8种蚂蚁与植株形成关联，其他捕食类群涵盖蜘蛛、瓢虫、膜翅目蜂类与半翅目昆虫。寄生性吸血蠓类（蠓科（Ceratopogonidae））与寄生蝇也与鳞翅目幼虫植食者存在关联，或也会利用植株的花外蜜腺。试验结果显示，蚂蚁的存在并未显著影响蝴蝶的产卵行为，各处理组中不同发育阶段的鳞翅目昆虫数量并无显著差异。但在蚂蚁被排除的植株上，观测到的高龄鳞翅目幼虫数量显著更多，表明蚂蚁可将小型幼虫从植株上清除。在蚂蚁被排除的植株上，其他捕食性类群（蜘蛛、瓢虫与蜂类）的种群数量显著更高。各处理组的寄生率并无显著差异，但对照植株上采集到的幼虫中，因病毒感染致死的个体数量显著更多。本研究罕见地解析了兼性蚁-植物共生关系与其重叠的多种其他交互作用的关联场景。研究结论表明，蚂蚁可为S. chapmanii上的植食性昆虫提供一定程度的生物防御，尽管蚂蚁会对非蚁类捕食者产生负面影响，但植株整体仍能从蚂蚁的存在中获益。