Data from: Effects of predatory ants within and across ecosystems in bromeliad food webs

Predation is one of the most fundamental ecological processes affecting biotic communities. Terrestrial predators that live at ecosystem boundaries may alter the diversity of terrestrial organisms, but they may also have cross-ecosystem cascading effects when they feed on organisms with complex life cycles (i.e. organisms that shift from aquatic juvenile stages to terrestrial adult stages) or inhibit female oviposition in the aquatic environment.
The predatory ant Odontomachus hastatus establishes its colonies among roots of Vriesea procera, an epiphytic bromeliad species with water-filled tanks that shelters many terrestrial and aquatic organisms. Ants may impact terrestrial communities and deter adult insects from ovipositing in the water of bromeliads via consumptive and non-consumptive effects. Ants do not forage within the aquatic environment; thus, they may be more efficient predators on terrestrial organisms. Therefore, we predict that ants will have stronger effects on terrestrial than aquatic food webs. However, such effects may also be site contingent and depend on the local composition of food webs.
To test our hypothesis, we surveyed bromeliads with and without O. hastatus colonies from three different coastal field sites in the Atlantic Forest of southeast Brazil, and quantified the effect of this predatory ant on the composition, density and richness of aquatic and terrestrial metazoans found in these bromeliads.
We found that ants changed the composition and reduced the overall density of aquatic and terrestrial metazoans in bromeliad ecosystems. However, effects of ants on species diversity were contingent on site. In general terms, the effects of the ant on aquatic and terrestrial metazoan communities were similar in strength and magnitude. Ants reduced the density of virtually all aquatic functional groups, especially detritivore insects as well as metazoans that reach bromeliads through phoresy on the skin of terrestrial animals (i.e. Ostracoda and Helobdella sp.).
Our results suggest that the cross-ecosystem effect of this terrestrial predator on the aquatic metazoans was at least as strong as its within-ecosystem effect on the terrestrial ecosystem, and demonstrates that the same predator can simultaneously initiate cascades in multiple ecosystems.

捕食作用是影响生物群落的最基础生态过程之一。栖息于生态系统边界的陆生捕食者，不仅能够改变陆生生物的多样性，还可通过捕食具有复杂生活史的生物（即从水生幼体阶段发育为陆生成体的生物），或在水生环境中抑制雌性个体产卵，进而产生跨生态系统级联效应。
捕食性蚂蚁钝颚家蚁（Odontomachus hastatus）会在附生凤梨科植物Vriesea procera的根系间筑巢；该类附生凤梨拥有储水腔，可为众多陆生与水生生物提供栖息场所。蚂蚁可通过消耗性与非消耗性效应，对陆生群落产生影响，并阻止成虫在凤梨科植物的储水中产卵。由于蚂蚁不会在水生环境中觅食，因此它们对陆生生物的捕食效率可能更高。据此我们预测，相较于水生食物网，蚂蚁对陆生食物网的作用强度更强。不过此类效应也具有生境依赖性，取决于当地食物网的组成结构。
为验证本研究假说，我们在巴西东南部大西洋森林的3处不同沿海野外样地中，调查了带有与不带钝颚家蚁蚁巢的凤梨科植物，并量化了该捕食性蚂蚁对这些凤梨生境中水生与陆生后生动物的群落组成、密度及物种丰富度的影响。
研究结果显示，蚂蚁改变了凤梨科植物生态系统中水生与陆生后生动物的群落组成，并降低了其总体密度。不过蚂蚁对物种多样性的作用效果具有生境依赖性。总体而言，蚂蚁对水生与陆生后生动物群落的作用强度与规模相似。蚂蚁几乎降低了所有水生功能群的密度，尤其是食腐昆虫，以及通过陆生动物体表携播进入凤梨生境的后生动物（即介形纲（Ostracoda）与舌蛭属（Helobdella sp.）物种）。
我们的研究结果表明，该陆生捕食者对水生后生动物的跨生态系统效应，至少与其对陆生生态系统的内部生态系统效应强度相当，同时证明了同一捕食者可同时在多个生态系统中引发级联效应。