title: Food web structure shaped by habitat size and climate across a latitudinal gradient.
abstract: Habitat size and climate are known to affect the trophic structure and dynamics of communities, but their interactive effects are poorly understood. Organisms from different trophic levels vary in terms of metabolic requirements and heat dissipation. Indeed, larger species such as keystone predators require more stable climatic conditions than their prey. Likewise, habitat size disproportionally affects large-sized predators, which require larger home ranges and are thus restricted to larger habitats. Therefore, food web structure in patchy ecosystems is expected to be shaped by habitat size and climate variations. Here we investigate this prediction using natural aquatic microcosm (bromeliad phytotelmata) food webs composed of litter resources (mainly detritus), detritivores, mesopredators, and top predators (damselflies). We surveyed 240 bromeliads of varying sizes (water retention capacity) across 12 open restingas in SE Brazil spread across a wide range of tropical latitudes (-12.6° to -27.6°, ca. 2,000 km) and climates (Δ mean annual temperature = 5.3°C). We found a strong increase in predator-to-detritivore mass ratio with habitat size, which was representative of a typical inverted trophic pyramid in larger ecosystems. However, this relationship was contingent among the restingas; slopes of linear models were steeper in more stable and favorable climates, leading to inverted trophic pyramids (and top-down control) being more pronounced in environments with more favorable climatic conditions. By contrast, detritivore-resource and mesopredator-detritivore mass ratios were not affected by habitat size or climate variations across latitudes. Our results highlight that the combined effects of habitat size, climate and predator composition are pivotal to understanding the impacts of multiple environmental factors on food web structure and dynamics.
authors.affiliation: Laboratory of Multitrophic Interactions and Biodiversity (LIMBIO), Department of Animal Biology, Institute of Biology, University of Campinas (UNICAMP), CP 6109, Campinas, SP, 13083-970, Brazil.|Brazilian Research Network on Climate Change (Rede Clima).
authors.forename: Gustavo Q
authors.initials: GQ
authors.lastname: Romero
authors.affiliation: Laboratory of Multitrophic Interactions and Biodiversity (LIMBIO), Department of Animal Biology, Institute of Biology, University of Campinas (UNICAMP), CP 6109, Campinas, SP, 13083-970, Brazil.
authors.forename: Gustavo C O
authors.initials: GC
authors.lastname: Piccoli
authors.affiliation: Laboratory of Multitrophic Interactions and Biodiversity (LIMBIO), Department of Animal Biology, Institute of Biology, University of Campinas (UNICAMP), CP 6109, Campinas, SP, 13083-970, Brazil.
authors.forename: Paula M
authors.initials: PM
authors.lastname: de Omena
authors.affiliation: Laboratory of Phylogenetic and Functional Ecology (ECOFFUN), Department of Biology, Area of Ecology, Federal Rural University of Pernambuco (UFRPE), R. Dom Manoel de Medeiros s/n, Recife, PE, 52171-900, Brazil.
authors.forename: Thiago
authors.initials: T
authors.lastname: Gonçalves-Souza
mesh_terms: D000818:Animals; D001938:Brazil; D017753:Ecosystem; D020387:Food Chain; D011235:Predatory Behavior
keywords: Brazilian restingas; bromeliad food webs; climatic stability; freshwater ecology; global changes; habitat size; inverted trophic pyramids; keystone predators; latitudinal gradient; mesopredators