Falcão P F, Pinto S R R, Wirth R, Leal I R
Programa de Pós-Graduação em Biologia Vegetal, Universidade Federal de Pernambuco, Avenida Professor Moraes Rego s/n, Cidade Universitária, Recife, PE, Brazil.
Bull Entomol Res. 2011 Jun;101(3):305-11. doi: 10.1017/S000748531000043X. Epub 2010 Nov 1.
Much of the ecological alteration faced by human-modified Neotropical forests can be assigned to edge effects, including the proliferation of some voracious herbivores such as leaf-cutting ants. However, the underlying mechanisms/impacts of tropical forest edge on herbivores performance and their foraging behaviour (e.g. dietary diversity) have rarely been investigated. The goal of this study was, therefore, to determine whether and how the annual diet (i.e. species richness, diversity and the relative proportion of pioneer versus non-pioneer species of plant materials) of Atta cephalotes colonies differs in the forest edge versus the interior zone of a large remnant of Atlantic forest in northeastern Brazil. Among the key results was a strong habitat effect on dietary diversity (explaining ca. 40-50% of the variation), which, in edge colonies, decreased approximately by one fourth compared to interior colonies (inverse of Simpson's index: 3.7±0.84 versus 4.99±0.95). There was a predominance of leaf fragments collected from pioneer species in the diet in both habitat (86% in edge and 80.4% in interior). Edge colonies collected proportionally more fragments from pioneer species than colonies located in the forest interior. Our results are the first to demonstrate an edge-mediated relaxation of dietary restrictions in leaf-cutting ants. These findings render robust support to previous evidence indicating the reduction of bottom-up forces as a key factor explaining both edge-induced hyper-abundance and increased herbivory of leaf-cutting ants in human-modified Neotropical landscapes.
人类改造后的新热带森林所面临的许多生态变化可归因于边缘效应，包括一些贪婪的食草动物（如切叶蚁）的大量繁殖。然而，热带森林边缘对食草动物表现及其觅食行为（如饮食多样性）的潜在机制/影响很少得到研究。因此，本研究的目的是确定巴西东北部一大片残余大西洋森林边缘地带与内部区域的切叶蚁蚁群的年度食物组成（即植物材料中先锋物种与非先锋物种的物种丰富度、多样性及相对比例）是否存在差异以及如何存在差异。其中的关键结果是栖息地对饮食多样性有强烈影响（解释了约40%-50%的变异），与内部蚁群相比，边缘蚁群的饮食多样性大约降低了四分之一（辛普森指数倒数：3.7±0.84对4.99±0.95）。在这两种栖息地中，饮食中从先锋物种采集的叶片碎片都占主导地位（边缘为86%，内部为80.4%）。边缘蚁群比森林内部的蚁群按比例从先锋物种采集的碎片更多。我们的研究结果首次证明了边缘介导的切叶蚁饮食限制的放松。这些发现有力地支持了先前的证据，表明自下而上力量的减弱是解释人类改造的新热带景观中边缘诱导的切叶蚁数量过多和食草量增加的关键因素。
