DOI: 10.5061/dryad.6k939m4
title: Data from: Interactions among predators and plant specificity protects herbivores from top predators

description: The worldwide loss of top predators from natural and agricultural systems
 has heightened the need to understand how important they are in
 controlling herbivore abundance. The effect of top predators on herbivore
 species is likely to depend on 1) the importance of the consumption of
 intermediate predators by top predators (intra-guild predation; IGP), but
 also on 2) plant specificity by herbivores, because specialists may defend
 themselves better (enemy-free space; EFS). Insectivorous birds, as top
 predators, are generally known to effectively control herbivorous insects,
 despite also consuming intermediate predators such as spiders, but how
 this effect varies among herbivore species in relation to the cascading
 effects of IGP and EFS is not known. To explore this, we excluded birds
 from natural fynbos vegetation in South Africa using large netted cages
 and recorded changes in abundance relative to control plots for 199
 plant-dwelling intermediate predator and 341 herbivore morpho-species that
 varied in their estimated plant specificity. We found a strong negative
 effect of birds on the total abundance of all intermediate predators, with
 especially clear effects on spiders (strong IGP). In contrast with
 previous studies, which document a negative effect of birds on herbivores,
 we found an overall neutral effect of birds on herbivore abundance, but
 the effect varied among species: some species were negatively affected by
 birds, suggesting that they were mainly consumed by birds, whereas others,
 likely released from spiders by IGP, were positively affected. Some
 species were also effectively neutrally affected by birds. These tended to
 be more specialized to plants compared to the other species, which may
 imply that some plant specialists benefited from protection provided by
 EFS from both birds and spiders. These results suggest that the response
 of herbivore species to top predators may depend on cascading effects of
 interactions among predators and on their degree of plant specificity.
description: ArthropodAbundances_BirdExpe_Dec2014Number of individuals per quadrat for arthropod morpho-species collected on the vegetation at Jonkershoek on December 2014 for a "bird exclosure" experiment.ArthropodTaxonomy_BirdExpe_Dec2014Taxonomy of arthropods collected on the vegetation at Jonkershoek on December 2014 for a "bird exclosure" experiment.ArthropodTrophicGroup_BirdExpe_Dec2014Mean body length (in mm), developmental stage and trophic group of arthropod morpho-species collected on the vegetation at Jonkershoek on December 2014 for a "bird exclosure" experiment.ExpeDesign_BirdExpe_Dec2014Treatment, site and slope factors; experimental design of a "bird exclosure" experiment conducted at Jonkershoek on December 2014.PlantCovers_m2_BirdExpe_Dec2014Cover (in m2) per quadrat for plant morpho-species sampled at Jonkershoek on December 2014 for a "bird exclosure" experiment.PlantTaxonomy_BirdExpe_Dec2014Taxonomy of plants sampled at Jonkershoek on December 2014 for a "bird exclosure" experiment.Script_BirdExpe_EcologyR scriptArthropodPhotographs_ChristopherBosc_thesisPhotographs of arthropods collected on the vegetation at Jonkershoek on December 2014 (six year old vegetation (post-fire age)) for a "bird exclosure" experiment. + Photographs of arthropods collected on the vegetation at Jonkershoek on August 2015, December 2015, August 2016 and December 2016 after a fire occuring in March 2015.PlantPhotographs_ChristopherBosc_thesisPhotographs of plants sampled at Jonkershoek on December 2014 for a "bird exclosure" experiment. + Photographs of plants sampled at Jonkershoek on August 2015, December 2015, August 2016 and December 2016 after a fire occuring in March 2015.