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Spatially heterogeneous perturbations homogenize the regulation of insect herbivores


Harvey, Eric; MacDougall, Andrew S (2015). Spatially heterogeneous perturbations homogenize the regulation of insect herbivores. The American Naturalist, 186(5):623-633.

Abstract

Anthropogenic influences on resources and consumers can affect food web regulation, with impacts on trophic structure and ecosystem processes. Identifying how these impacts unfold is challenging because alterations to one or both resources and consumers can similarly transform community structure, especially for intermediate consumers. To date, empirical testing of perturbations on trophic regulation has been limited by the difficulty in separating the direct effect of perturbations on species composition and diversity versus those unfolding indirectly via altered feeding pathways. Moreover, disentangling the independent and interactive impacts of co-varying stressors that characterize human-altered systems has been an ongoing analytical challenge. We used a large-scale meta-community experiment in grasslands to test how resource inputs, stand perturbation, and spatial factors affect regulation of insect herbivores in tri-trophic grassland food webs. Using path-model comparisons, we observed significant simplification of food web regulation on insect herbivores, shifting from mixed predator-resource regulation in unaltered mainland areas, to strictly resource-based regulation with landscape perturbation and fragmentation. Most changes were attributed to homogenization of plant community caused by landscape fragmentation and the deterministic influence of eutrophication that reduced among-patch beta-diversity. This led to a simplified food web dominated by fewer, but more abundant herbivore taxa. Our work implies that anthropogenic perturbation relating to resources and spatial isolation can transform the regulation of food web diversity, structure and function.

Abstract

Anthropogenic influences on resources and consumers can affect food web regulation, with impacts on trophic structure and ecosystem processes. Identifying how these impacts unfold is challenging because alterations to one or both resources and consumers can similarly transform community structure, especially for intermediate consumers. To date, empirical testing of perturbations on trophic regulation has been limited by the difficulty in separating the direct effect of perturbations on species composition and diversity versus those unfolding indirectly via altered feeding pathways. Moreover, disentangling the independent and interactive impacts of co-varying stressors that characterize human-altered systems has been an ongoing analytical challenge. We used a large-scale meta-community experiment in grasslands to test how resource inputs, stand perturbation, and spatial factors affect regulation of insect herbivores in tri-trophic grassland food webs. Using path-model comparisons, we observed significant simplification of food web regulation on insect herbivores, shifting from mixed predator-resource regulation in unaltered mainland areas, to strictly resource-based regulation with landscape perturbation and fragmentation. Most changes were attributed to homogenization of plant community caused by landscape fragmentation and the deterministic influence of eutrophication that reduced among-patch beta-diversity. This led to a simplified food web dominated by fewer, but more abundant herbivore taxa. Our work implies that anthropogenic perturbation relating to resources and spatial isolation can transform the regulation of food web diversity, structure and function.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Evolutionary Biology and Environmental Studies
Dewey Decimal Classification:570 Life sciences; biology
590 Animals (Zoology)
Language:English
Date:November 2015
Deposited On:05 Feb 2016 14:06
Last Modified:19 Sep 2016 00:00
Publisher:University of Chicago Press
ISSN:0003-0147
Additional Information:© 2015 by The University of Chicago
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1086/683199
PubMed ID:26655775

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