title: Tropical forest loss and its multitrophic effects on insect herbivory.
abstract: Forest loss threatens biodiversity, but its potential effects on multitrophic ecological interactions are poorly understood. Insect herbivory depends on complex bottom-up (e.g., resource availability and plant antiherbivore defenses) and top-down forces (e.g., abundance of predators and herbivorous), but its determinants in human-altered tropical landscapes are largely unknown. Using structural equation models, we assessed the direct and indirect effects of forest loss on insect herbivory in 40 landscapes (115 ha each) from two regions with contrasting land-use change trajectories in the Brazilian Atlantic rainforest. We considered landscape forest cover as an exogenous predictor and (1) forest structure, (2) abundance of predators (birds and arthropods), and (3) abundance of herbivorous arthropods as endogenous predictors of insect leaf damage. From 12 predicted pathways, 11 were significant and showed that (1) leaf damage increases with forest loss (direct effect); (2) leaf damage increases with forest loss through the simplification of vegetation structure and its associated dominance of herbivorous insects (indirect effect); and further demonstrate (3) a lack of top-down control of herbivores by predators (birds and arthropods). We conclude that forest loss favors insect herbivory by undermining the bottom-up control (presumably reduced plant antiherbivore defense mechanisms) in forests dominated by fast-growing pioneer plant species, and by improving the conditions required for herbivores proliferation.
authors.affiliation: Applied Conservation Ecology Lab, Programa de Pós-graduação Ecologia e Conservação da Biodiversidade, Universidade Estadual de Santa Cruz, Rodovia Ilhéus-Itabuna, km 16, Salobrinho, 45662-000, Ilhéus, Bahia, Brazil.
authors.forename: José Carlos
authors.initials: JC
authors.lastname: Morante-Filho
authors.affiliation: Instituto de Investigaciones en Ecosistemas y Sustentabilidad, Universidad Nacional Autónoma de México, 58190, Morelia, Michoacán, Mexico.
authors.forename: Víctor
authors.initials: V
authors.lastname: Arroyo-Rodríguez
authors.affiliation: Forest Ecology and Forest Management Group, Wageningen University, P.O. Box 47, 6700AA, Wageningen, The Netherlands.|World Agroforestry Centre (ICRAF), PO Box 30677-00100, Nairobi, Kenya.
authors.forename: Madelon
authors.initials: M
authors.lastname: Lohbeck
authors.affiliation: Agroecology, Georg-August-University Göttingen, Göttingen, Germany.
authors.forename: Teja
authors.initials: T
authors.lastname: Tscharntke
authors.affiliation: Applied Conservation Ecology Lab, Programa de Pós-graduação Ecologia e Conservação da Biodiversidade, Universidade Estadual de Santa Cruz, Rodovia Ilhéus-Itabuna, km 16, Salobrinho, 45662-000, Ilhéus, Bahia, Brazil.
authors.forename: Deborah
authors.initials: D
authors.lastname: Faria
mesh_terms: D000818:Animals; D020387:Food Chain; D065928:Forests; D060434:Herbivory / Q000502:physiology*; D007313:Insecta / Q000502:physiology*; D008954:Models, Biological; D014329:Tropical Climate; D014714:Vertebrates / Q000502:physiology*
keywords: Atlantic rainforest; bottom-up control; defaunation; deforestation; forest fragmentation; leaf damage; top-down control