Experimental Removal of Insectivores from Rain Forest Canopy: Direct and Indirect Effects

Dial, Roman; Roughgarden, Jonathan

doi:10.2307/1940714

Cited by 116 publications

(106 citation statements)

References 24 publications

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“…Despite omnivory and potential compensation, then, the effects of bird predation were strong enough to produce indirect effects on trees. Our bird study joins recent empirical demonstrations of strong predator effects in other terrestrial tropical food webs, with arthropod (21), reptilian (22,23), and mammalian (24) predators.…”

Section: Discussionsupporting

confidence: 64%

Birds defend trees from herbivores in a Neotropical forest canopy

Bael

Brawn

Robinson

2003

Proc. Natl. Acad. Sci. U.S.A.

191

167

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Most forest birds include arthropods in their diet, sometimes specializing on arthropods that consume plant foliage. Experimental tests of whether bird predation on arthropods can reduce plant damage, however, are few and restricted to relatively low-diversity systems. Here, we describe an experimental test in a diverse tropical forest of whether birds indirectly defend foliage from arthropod herbivores. We also compare how the indirect effects of bird predation vary with different levels of foliage productivity in the canopy vs. the understory. For three Neotropical tree species, we observed that birds decreased local arthropod densities on canopy branches and reduced consequent damage to leaves. In contrast, we observed no evidence of bird-arthropod limitation on conspecific saplings in the less productive understory of the same forest. Our results support theory that predicts trophic cascades where productivity is high and suggest that birds play an important role in Neotropical communities by means of their indirect defense of some canopy tree species.F or decades, ecologists have debated the circumstances under which a predator limits its prey's consumption of organisms in lower trophic levels (i.e., a predator-driven trophic cascade) (1-4). One body of theory predicts such cascades will occur in terrestrial systems with high plant productivity (5, 6). Opposing theory predicts that cascades will not occur in terrestrial systems and only in low-diversity aquatic or marine systems (7). Proponents of the latter theory suggest that higher diversity in terrestrial systems leads to diffuse food webs, rendering trophic levels nonexistent (7). Field experiments demonstrate that insectivorous birds can limit arthropod abundances and decrease damage to plants, but these tests have been conducted in settings with relatively low tree species diversity such as temperate forests (8-11) or agricultural systems (12, 13). Along with high tree species diversity, tropical forests support a high diversity and biomass of leaf-chewing arthropods (14) as well as a high biomass of birds that consume them (15). In a lowland forest of Panama, we used canopy crane access (16) to test the hypotheses that (i) birds limit arthropod densities and consequent herbivore damage, and (ii) the effects of bird predation are strongest where foliage production rates are high.For one year, we observed how the local density and taxonomic composition of the arthropod community responded to the absence of bird predation and also assessed changes in herbivore damage. We estimated and compared these quantities on control branches͞saplings where birds had access to foliage and on branches͞saplings in experimental exclosures where foliage was inaccessible to birds. A within-site comparison of canopy branches and conspecific understory͞edge saplings allowed us to investigate the effects of bird predation across a 3-fold vertical gradient of foliage production. MethodsA canopy crane provided forest canopy access in a dry, semideciduous lowland tropical for...

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Section: Discussionsupporting

confidence: 64%

Birds defend trees from herbivores in a Neotropical forest canopy

Bael

Brawn

Robinson

2003

Proc. Natl. Acad. Sci. U.S.A.

191

167

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“…All 80 sites were at least 250 m apart to control for the home range territories of primary Heliconius avian predators. Predator home range sizes vary between 100 and 250 m, and have been determined by other researchers through radio tracking (flycatchers [54]), harmonic distance method and core area use (tanagers [55]), minimum convex polygon modelling (flycatchers [54]) and observation (tanagers [56]; jacamars [57] was applied to the base of plant stems containing artificial butterflies to avoid removal or attack of the models by ants and other small arthropods, and it was also effective in preventing small vertebrates such as lizards from reaching the butterfly models [58]. The models were left at their sites for a total of 96 h (4 days), and each model was examined daily for predation evidence and replaced if attacked.…”

Section: (D) Predation Experimentsmentioning

confidence: 99%

The benefit of being a social butterfly: communal roosting deters predation

2012

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Aposematic passion-vine butterflies from the genus Heliconius form communal roosts on a nightly basis. This behaviour has been hypothesized to be beneficial in terms of information sharing and/or antipredator defence. To better understand the adaptive value of communal roosting, we tested these two hypotheses in field studies. The information-sharing hypothesis was addressed by examining following behaviour of butterflies departing from natural roosts. We found no evidence of roost mates following one another to resources, thus providing no support for this hypothesis. The anti-predator defence hypothesis was tested using avian-indiscriminable Heliconius erato models placed singly and in aggregations at field sites. A significantly higher number of predation attempts were observed on solitary models versus aggregations of models. This relationship between aggregation size and attack rate suggests that communally roosting butterflies enjoy the benefits of both overall decreased attack frequency as well as a prey dilution effect. Communal roosts probably deter predators through collective aposematism in which aggregations of conspicuous, unpalatable prey communicate a more effective repel signal to predators. On the basis of our results, we propose that predation by birds is a key selective pressure maintaining Heliconius communal roosting behaviour.

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“…Thus, we measured all arthropods encountered in our surveys as potential green anole prey. We used two methods to quantify arthropod abundance and biomass in each plot (following Dial and Roughgarden, 1995). In the first, we sampled primarily flying insects with Catchmaster ® traps, 5 in x 7 in cardboard rectangles coated on one side with a glue-like material.…”

Section: Arthropod Abundance and Biomassmentioning

confidence: 99%

“…Abundance and biomass of the six most common arthropod orders in the three study plots. Each of these orders is used as food by Anolis lizard species (Dial and Roughgarden, 1995). Light gray symbols represent data from the Field plot, dark gray symbols represent the Lake plot, and black symbols represent the Palmetto plot.…”

Section: Lizard Territory Size and Behaviormentioning

confidence: 99%

Prey availability affects territory size, but not territorial display behavior, in green anole lizards

et al. 2017

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. (2017). Prey availability affects territory size, but not territorial display behavior, in green anole lizards. Acta Oecologica, 84, 41-47. doi: 10.1016Oecologica, 84, 41-47. doi: 10. /j.actao.2017 Prey availability affects territory size, but not territorial display behavior, in green anole lizards The availability of food resources can affect the size and shape of territories, as well as the behaviors used to defend territories, in a variety of animal taxa. However, individuals within a population may respond differently to variation in food availability if the benefits of territoriality vary among those individuals. For example, benefits to territoriality may differ for animals of differing sizes, because larger individuals may require greater territory size to acquire required resources, or territorial behavior may differ between the sexes if males and females defend different resources in their territories. In this study, we tested whether arthropod abundance and biomass were associated with natural variation in territory size and defense in insectivorous green anole lizards, Anolis carolinensis. Our results showed that both male and female lizards had smaller territories in a habitat with greater prey biomass than lizards in habitats with less available prey, but the rates of aggressive behaviors used to defend territories did not differ among these habitats. Further, we did not find a relationship between body size and territory size, and the sexes did not differ in their relationships between food availability and territory size or behavioral defense. Together, these results suggest that differences in food availability influenced male and female territorial strategies similarly, and that territory size may be more strongly associated with variation in food resources than social display behavior. Thus, anole investment in the behavioral defense of a territory may not vary with territory quality.

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Experimental Removal of Insectivores from Rain Forest Canopy: Direct and Indirect Effects

Cited by 116 publications

References 24 publications

Birds defend trees from herbivores in a Neotropical forest canopy

Birds defend trees from herbivores in a Neotropical forest canopy

The benefit of being a social butterfly: communal roosting deters predation

Prey availability affects territory size, but not territorial display behavior, in green anole lizards

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