Local, landscape, and diversity drivers of predation services provided by ants in a coffee landscape in Chiapas, Mexico

Agricultural management and the landscape surrounding farms impact biological diversity and ecosystem services, such as predation, in agroecosystems. Diversified coffee agroecosystems harbor biodiversity, and maintain ecosystem services, especially when in complex landscapes, and when diversity of organisms providing services is maintained. But few have examined whether biological diversity, per se, or the local and landscape habitat features are stronger drivers of the services provided. We studied the relationships between local characteristics associated with agricultural management (vegetation complexity and agrochemical use), landscape surroundings of farms, abundance and richness of ants, and predation services provided by ants in a tropical coffee landscape. Specifically, we tested whether: (1) ants remove prey items and prey removal differs in the wet and dry season, (2) ant prey removal differs in farms that vary in vegetation complexity and agrochemical use, (3) ant prey removal differs with changes in ant abundance and species richness, and (4) ant prey removal differs with changes in local and landscape characteristics. We established sites across a range of coffee management systems, at varying distances to forest fragments, and in forest fragments and examined prey removal by ants on the ground, coffee branches, and shade tree trunks in the wet and dry season. Prey removal did not differ with season. Prey removal on the ground increased within increases in ant abundance and richness, and number of hollow coffee twigs. Prey removal on coffee plants decreased with vegetation complexity, but increased with ant abundance and richness, coffee density (a local factor), and rustic coffee within 200m (a landscape factor). Prey removal on trees declined with vegetation complexity, but increased with abundance and richness of ants. Characteristics of the ant community were consistent predictors of prey removal, whereas local and landscape habitat features were less important, and only three habitat features correlated with prey removal. Our results demonstrate the positive effects of ant diversity for predatory function, and that promoting pest control services within coffee agroecosystems may be best accomplished by manipulating ant abundance and richness, or vegetation factors that correlate with ants

Local, landscape, and diversity drivers of predation services provided by ants in a coffee landscape in Chiapas, Mexico

Agricultural management and the landscape surrounding farms impact biological diversity and ecosystem services, such as predation, in agroecosystems. Diversified coffee agroecosystems harbor biodiversity, and maintain ecosystem services, especially when in complex landscapes, and when diversity of organisms providing services is maintained. But few have examined whether biological diversity, per se, or the local and landscape habitat features are stronger drivers of the services provided. We studied the relationships between local characteristics associated with agricultural management (vegetation complexity and agrochemical use), landscape surroundings of farms, abundance and richness of ants, and predation services provided by ants in a tropical coffee landscape. Specifically, we tested whether: (1) ants remove prey items and prey removal differs in the wet and dry season, (2) ant prey removal differs in farms that vary in vegetation complexity and agrochemical use, (3) ant prey removal differs with changes in ant abundance and species richness, and (4) ant prey removal differs with changes in local and landscape characteristics. We established sites across a range of coffee management systems, at varying distances to forest fragments, and in forest fragments and examined prey removal by ants on the ground, coffee branches, and shade tree trunks in the wet and dry season. Prey removal did not differ with season. Prey removal on the ground increased within increases in ant abundance and richness, and number of hollow coffee twigs. Prey removal on coffee plants decreased with vegetation complexity, but increased with ant abundance and richness, coffee density (a local factor), and rustic coffee within 200m (a landscape factor). Prey removal on trees declined with vegetation complexity, but increased with abundance and richness of ants. Characteristics of the ant community were consistent predictors of prey removal, whereas local and landscape habitat features were less important, and only three habitat features correlated with prey removal. Our results demonstrate the positive effects of ant diversity for predatory function, and that promoting pest control services within coffee agroecosystems may be best accomplished by manipulating ant abundance and richness, or vegetation factors that correlate with ants

Effects of predatory ants on lower trophic levels across a gradient of coffee management complexity

1.   Ants are important predators in agricultural systems, and have complex and often strong effects on lower trophic levels. Agricultural intensification reduces habitat complexity, food web diversity and structure, and affects predator communities. Theory predicts that strong top-down cascades are less likely to occur as habitat and food web complexity decrease. 2.   To examine relationships between habitat complexity and predator effects, we excluded ants from coffee plants in coffee agroecosystems varying in vegetation complexity. Specifically, we studied the effects of eliminating ants on arthropod assemblages, herbivory, damage by the coffee berry borer and coffee yields in four sites differing in management intensification. We also sampled ant assemblages in each management type to see whether changes in ant assemblages relate to any observed changes in top-down effects. 3.  Removing ants did not change total arthropod densities, herbivory, coffee berry borer damage or coffee yields. Ants did affect densities of some arthropod orders, but did not affect densities of different feeding groups. The effects of ants on lower trophic levels did not change with coffee management intensity. 4.  Diversity and activity of ants on experimental plants did not change with coffee intensification, but the ant species composition differed. 5.   Although variation in habitat complexity may affect trophic cascades, manipulating predatory ants across a range of coffee agroecosystems varying in management intensity did not result in differing effects on arthropod assemblages, herbivory, coffee berry borer attack or coffee yields. Thus, there is no clear pattern that top-down effects of ants in coffee agroecosystems intensify or dampen with decreased habitat complexity.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71478/1/j.1365-2656.2008.01358.x.pd

Contribution of cocoa plantations to the conservation of native ants (Insecta: Hymenoptera: Formicidae) with a special emphasis on the Atlantic Forest fauna of southern Bahia, Brazil

International audienc

Bird and bat predation services in tropical forests and agroforestry landscapes

Understanding distribution patterns and multitrophic interactions is critical for managing bat- and bird-mediated ecosystem services such as the suppression of pest and non-pest arthropods. Despite the ecological and economic importance of bats and birds in tropical forests, agroforestry systems, and agricultural systems mixed with natural forest, a systematic review of their impact is still missing. A growing number of bird and bat exclosure experiments has improved our knowledge allowing new conclusions regarding their roles in food webs and associated ecosystem services. Here, we review the distribution patterns of insectivorous birds and bats, their local and landscape drivers, and their effects on trophic cascades in tropical ecosystems. We report that for birds but not bats community composition and relative importance of functional groups changes conspicuously from forests to habitats including both agricultural areas and forests, here termed ‘forest-agri’ habitats, with reduced representation of insectivores in the latter. In contrast to previous theory regarding trophic cascade strength, we find that birds and bats reduce the density and biomass of arthropods in the tropics with effect sizes similar to those in temperate and boreal communities. The relative importance of birds versus bats in regulating pest abundances varies with season, geography and management. Birds and bats may even suppress tropical arthropod outbreaks, although positive effects on plant growth are not always reported. As both bats and birds are major agents of pest suppression, a better understanding of the local and landscape factors driving the variability of their impact is needed

Bird and bat predation services in tropical forests and agroforestry landscapes

Understanding distribution patterns and multitrophic interactions is critical for managing bat- and bird-mediated ecosystem services such as the suppression of pest and non-pest arthropods. Despite the ecological and economic importance of bats and birds in tropical forests, agroforestry systems, and agricultural systems mixed with natural forest, a systematic review of their impact is still missing. A growing number of bird and bat exclosure experiments has improved our knowledge allowing new conclusions regarding their roles in food webs and associated ecosystem services. Here, we review the distribution patterns of insectivorous birds and bats, their local and landscape drivers, and their effects on trophic cascades in tropical ecosystems. We report that for birds but not bats community composition and relative importance of functional groups changes conspicuously from forests to habitats including both agricultural areas and forests, here termed ‘forest-agri’ habitats, with reduced representation of insectivores in the latter. In contrast to previous theory regarding trophic cascade strength, we find that birds and bats reduce the density and biomass of arthropods in the tropics with effect sizes similar to those in temperate and boreal communities. The relative importance of birds versus bats in regulating pest abundances varies with season, geography and management. Birds and bats may even suppress tropical arthropod outbreaks, although positive effects on plant growth are not always reported. As both bats and birds are major agents of pest suppression, a better understanding of the local and landscape factors driving the variability of their impact is needed