Food web structure shaped by habitat size and climate across a latitudinal gradient

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)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 degrees to -27.6 degrees, ca. 2,000km) and climates ( mean annual temperature=5.3 degrees 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.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. Inde971027052715FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFINANCIADORA DE ESTUDOS E PROJETOS - FINEPFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)sem informação550022/2014- 701.13.0353.00The authors thank three anonymous reviewers for the valua-ble comments on the first edition of this report. A. L. Mendonça helped with invertebrate surveys, and identifications were con-ducted by L. C. de Pinho (Chironomidae), A. L. Mendonça (Culicidae), M

Species niches, not traits, determine abundance and occupancy patterns: A multi‐site synthesis

International audienceAim: Locally abundant species are usually widespread, and this pattern has been related to properties of the niches and traits of species. However, such explanations fail to account for the potential of traits to determine species niches and often overlook statistical artefacts. Here, we examine how trait distinctiveness determines the abilities of species to exploit either common habitats (niche position) or a range of habitats (niche breadth) and how niche position and breadth, in turn, affect abundance and occupancy. We also examine how statistical artefacts moderate these relationships. Location: Sixteen sites in the Neotropics. Time period 1993–2014. Major taxa studied Aquatic invertebrates from tank bromeliads. Methods: We measured the environmental niche position and breadth of each species and calculated its trait distinctiveness as the average trait difference from all other species at each site. Then, we used a combination of structural equation models and a meta-analytical approach to test trait–niche relationships and a null model to control for statistical artefacts. Results: The trait distinctiveness of each species was unrelated to its niche properties, abundance and occupancy. In contrast, niche position was the main predictor of abundance and occupancy; species that used the most common environmental conditions found across bromeliads were locally abundant and widespread. Contributions of niche breadth to such patterns were attributable to statistical artefacts, indicating that effects of niche breadth might have been overestimated in previous studies. Main conclusions: Our study reveals the generality of niche position in explaining one of the most common ecological patterns. The robustness of this result is underscored by the geographical extent of our study and our control of statistical artefacts. We call for a similar examination across other systems, which is an essential task to understand the drivers of commonness across the tree of life

How much leaf area do insects eat? A data set of insect herbivory sampled globally with a standardized protocol

Herbivory is ubiquitous. Despite being a potential driver of plant distribution and performance, herbivory remains largely undocumented. Some early attempts have been made to review, globally, how much leaf area is removed through insect feeding. Kozlov et al., in one of the most comprehensive reviews regarding global patterns of herbivory, have compiled published studies regarding foliar removal and sampled data on global herbivory levels using a standardized protocol. However, in the review by Kozlov et al., only 15 sampling sites, comprising 33 plant species, were evaluated in tropical areas around the globe. In Brazil, which ranks first in terms of plant biodiversity, with a total of 46,097 species, almost half (43%) being endemic, a single data point was sampled, covering only two plant species. In an attempt to increase knowledge regarding herbivory in tropical plant species and to provide the raw data needed to test general hypotheses related to plant–herbivore interactions across large spatial scales, we proposed a joint, collaborative network to evaluate tropical herbivory. This network allowed us to update and expand the data on insect herbivory in tropical and temperate plant species. Our data set, collected with a standardized protocol, covers 45 sampling sites from nine countries and includes leaf herbivory measurements of 57,239 leaves from 209 species of vascular plants belonging to 65 families from tropical and temperate regions. They expand previous data sets by including a total of 32 sampling sites from tropical areas around the globe, comprising 152 species, 146 of them being sampled in Brazil. For temperate areas, it includes 13 sampling sites, comprising 59 species

Fine-scale microhabitat selection in a bromeliad-dwelling jumping spider (Salticidae)

Although a wide variety of arthropods specialize on a specific host plant, little is known about the evolution of host-plant specialization in spiders. In several regions of South America, the Neotropical jumping spider Psecas chapoda associates with Bromelia balansae, a rosette-shaped plant that does not accumulate rain water in phytotelmata. We conducted experiments using bromeliad species with distinct architectures that were uncommon in the geographic range of R chapoda to investigate the level of spider specialization in microhabitat structure. We also tested the influence of phytotelmata and foliar spines on host plant selection. B. balansae, Ananas comosus and Aechmea distichantha (tank-bromeliad), which share similar traits (e.g. long and narrow leaves), were colonized in similar frequencies. Aechmea fasciata, a tank-bromeliad that has short and broad leaves, was never colonized by these spiders, and Aechmea blanchetiana, tank-bromeliad with long and broad leaves, was only colonized infrequently. The removal of foliar spines did not affect the number of R chapoda on B. balansae. Our findings suggest that microhabitat specialization by R chapoda is based on rosette and leaf architectures. This unusual specialization likely evolved because the bromeliads with such architecture (i.e. B. balansae) typically dominate the biogeographic area of R chapoda, and because this microhabitat provides specific benefits to spiders, as shelter, and as foraging and reproductive sites. (c) 2008 The Linnean Society of London.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Consumptive effects and mismatch in predator-prey turnover rates cause inversion of biomass pyramids

The mismatch between the turnover rates of predators and prey is one of the oldest explanations for the existence of inverted trophic pyramids. To date, the hypotheses regarding trophic pyramids have all been based on consumptive trophic links between predators and prey, and the relative contribution of non-consumptive effects is still unknown. In this study, we investigated if the inversion of pyramids in bromeliad ecosystems is driven by (i) a rapid colonization of organisms having short cohort interval production (CPI), and (ii) the prevalence of consumptive or non-consumptive effects of top predators. We used a manipulative experiment to investigate the patterns of prey colonization and to partition the net effects of the dominant predator (damselfly larvae) on biomass pyramids into consumptive (uncaged damselfly larvae) and non-consumptive effects (caged damselfly larvae). Consumptive effects of damselflies strengthened the inversion of trophic pyramids. Non-consumptive effects, however, did not affect the shape of biomass pyramids. Instead, the rapid colonization of organisms with predominantly short CPI sustained the large biomass of top predators found in natural bromeliad ecosystems. Prey colonized bromeliads rapidly, but this high production was never visible as standing stock because damselflies reduce prey densities by more than a magnitude through direct consumption. Our study adds to the growing evidence that there are a variety of possible ways that biomass can be trophically structured. Moreover, we suggest that the strength of biomass pyramids inversion may change with the time of ecological succession as prey communities become more equitable1901159168CAPES - Coordenação de Aperfeiçoamento de Pessoal e Nível SuperiorCNPQ - Conselho Nacional de Desenvolvimento Científico e TecnológicoFAPESP – Fundação de Amparo à Pesquisa Do Estado De São PauloBEX 8377/12-0; 2014/04603-4não tem2009/51702-

Trait-mediated effects on flowers: Artificial spiders deceive pollinators and decrease plant fitness

Although predators can affect foraging behaviors of oral visitors, rarely is it known if these top-down effects of predators may cascade to plant fitness through trait-mediated interactions. In this study we manipulated artificial crab spiders on flowers of Rubus rosifolius to test the effects of predation risk on flower-visiting insects and strength of trait-mediated indirect effects to plant fitness. In addition, we tested which predator traits (e. g., forelimbs, abdomen) are recognized and avoided by pollinators. Total visitation rate was higher for control flowers than for flowers with an artificial crab spider. In addition, flowers with a sphere (simulating a spider abdomen) were more frequently visited than those with forelimbs or the entire spider model. Furthermore, the presence of artificial spiders decreased individual seed set by 42% and fruit biomass by 50%. Our findings indicate that pollinators, mostly bees, recognize and avoid flowers with predation risk; forelimbs seem to be the predator trait recognized and avoided by hymenopterans. Additionally, predator avoidance by pollinators resulted in pollen limitation, thereby affecting some components of plant fitness (fruit biomass and seed number). Because most pollinator species that recognized predation risk visited many other plant species, trait-mediated indirect effects of spiders cascading down to plant fitness may be a common phenomenon in the Atlantic rainforest ecosystem.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Appendix A. Flower-visiting insects (Hymenoptera and Lepidoptera) on Rubus rosifolius along 3200 minutes of direct observations in the field.

Flower-visiting insects (Hymenoptera and Lepidoptera) on Rubus rosifolius along 3200 minutes of direct observations in the field

Using visual cues of microhabitat traits to find home: the case study of a bromeliad-living jumping spider (Salticidae)

There are many examples of predators having specialized microhabitat requirements, but the sensory mechanisms by which predators detect, identify, and evaluate microhabitats are only poorly understood. The ability to use visual cues to select microhabitats was investigated using Psecas chapoda, a bromeliad-dwelling salticid spider. In this study, we manipulated real plants and photos of plants to test whether P. chapoda uses plant architecture to select host plants and whether visual cues alone are sufficient for them to select microhabitats. The use of photos on the experiment allowed us to exclude the potential influence of other cues, such as color and odor, on host plant selection by the spider. Our results showed that P. chapoda selects their microhabitat by evaluating architectural features of leaves and rosette of the host plants. Rosette-shaped plants (Agavaceae) were preferred over other types of plant architecture. Spiders showed a preference for photographs of rosette-shaped plants having narrow and long leaves, confirming that they can make these choices entirely on the basis of vision. These salticids can recognize and select microhabitats bearing specific architectural features, which possibly reflects an adaptation to choose microhabitats that are favorable to its survivorship. Copyright 2010, Oxford University Press.