Gonçalves Ana Z, Srivastava Diane S, Oliveira Paulo S, Romero Gustavo Q
Department of Botany, University of São Paulo, São Paulo, Brazil.
Department of Zoology & Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada.
J Anim Ecol. 2017 Jul;86(4):790-799. doi: 10.1111/1365-2656.12671. Epub 2017 Apr 27.
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.
捕食是影响生物群落的最基本生态过程之一。生活在生态系统边界的陆地捕食者可能会改变陆地生物的多样性，但当它们以具有复杂生命周期的生物（即从水生幼体阶段转变为陆地成体阶段的生物）为食或抑制水生环境中的雌性产卵时，也可能产生跨生态系统的级联效应。捕食性蚂蚁哈氏齿猛蚁在普氏弗里西凤梨的根部建立蚁群，普氏弗里西凤梨是一种附生凤梨科植物，其充满水的叶腋庇护着许多陆地和水生生物。蚂蚁可能会通过消费性和非消费性影响来影响陆地群落，并阻止成年昆虫在凤梨科植物的水中产卵。蚂蚁不在水生环境中觅食；因此，它们可能是陆地生物更高效的捕食者。因此，我们预测蚂蚁对陆地食物网的影响将比对水生食物网的影响更强。然而，这种影响也可能因地点而异，并取决于食物网的当地组成。为了检验我们的假设，我们调查了巴西东南部大西洋森林中三个不同沿海野外地点有无哈氏齿猛蚁蚁群的凤梨科植物，并量化了这种捕食性蚂蚁对这些凤梨科植物中发现的水生和陆地后生动物的组成、密度和丰富度的影响。我们发现蚂蚁改变了凤梨科生态系统中水生和陆地后生动物的组成，并降低了其总体密度。然而，蚂蚁对物种多样性的影响因地点而异。一般来说，蚂蚁对水生和陆地后生动物群落的影响在强度和程度上相似。蚂蚁几乎降低了所有水生功能组的密度，尤其是碎屑食性昆虫以及通过附着在陆地动物皮肤上（即介形纲动物和蛭蚓属物种）进入凤梨科植物的后生动物。我们的结果表明，这种陆地捕食者对水生后生动物的跨生态系统影响至少与其对陆地生态系统的生态系统内影响一样强烈，并表明同一捕食者可以同时在多个生态系统中引发级联效应。
