Human-induced trophic cascades along the fecal detritus pathway

Nichols, Elizabeth, Uriarte, Marã­a, Peres, Carlos A. ORCID: https://orcid.org/0000-0002-1588-8765, Louzada, Julio, Braga, Rodrigo Fagundes, Schiffler, Gustavo, Endo, Whaldener and Spector, Sacha H. (2013) Human-induced trophic cascades along the fecal detritus pathway. PLoS One, 8 (10). ISSN 1932-6203

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Abstract

Human presence and activity in tropical forest is thought to exert top-down regulation over the various ‘green-world’ pathways of plant-based foodwebs. However, these effects have never been explored for the ‘brown-world’ pathways of fecal-detritus webs. The strong effects of humans on tropical game mammals are likely to indirectly influence fecal detritivores (including Scarabaeine dung beetles), with subsequent indirect impacts on detrivore-mediated and plant-facilitating detrital processes. Across a 380-km gradient of human influence in the western Brazilian Amazon, we conducted the first landscape-level assessment of human-induced cascade effects on the fecal detritus pathway, by coupling data on human impact, game mammal and detritivore community structure, and rate measurements of a key detritus process (i.e. dung beetle-mediated secondary seed dispersal). We found evidence that human impact indirectly influences both the diversity and biomass of fecal detritivores, but not detritivore-mediated processes. Cascade strength varied across detritivore groups defined by species' traits. We found smaller-bodied dung beetles were at higher risk of local decline in areas of human presence, and that body size was a better predictor of cascade structure than fecal resource manipulation strategy. Cascade strength was also stronger in upland, unflooded forests, than in seasonally flooded forests. Our results suggest that the impact of human activity in tropical forest on fecal-detritus food web structure is mediated by both species' traits and habitat type. Further research will be required to determine the conditions under which these cascade effects influence fecal-detritus web function.

Item Type: Article
Additional Information: © 2013 Nichols et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Faculty \ School: Faculty of Science > School of Environmental Sciences
Depositing User: Pure Connector
Date Deposited: 01 Apr 2014 12:22
Last Modified: 27 Sep 2022 07:42
URI: https://ueaeprints.uea.ac.uk/id/eprint/48312
DOI: 10.1371/journal.pone.0075819

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