title: Multitrophic diversity effects of network degradation.
abstract: Predicting the functional consequences of biodiversity loss in realistic, multitrophic communities remains a challenge. No existing biodiversity-ecosystem function study to date has simultaneously incorporated information on species traits, network topology, and extinction across multiple trophic levels, while all three factors are independently understood as critical drivers of post-extinction network structure and function. We fill this gap by comparing the functional consequences of simulated species loss both within (monotrophic) and across (bitrophic) trophic levels, in an ecological interaction network estimated from spatially explicit field data on tropical fecal detritus producer and consumers (mammals and dung beetles). We simulated trait-ordered beetle and mammal extinction separately (monotrophic extinction) and the coextinction of beetles following mammal loss (bitrophic extinction), according to network structure. We also compared the diversity effects of bitrophic extinction models using a standard monotrophic function (the daily production or consumption of fecal detritus) and a unique bitrophic functional metric (the proportion of daily detritus production that is consumed). We found similar mono- and bitrophic diversity effects, regardless of which species traits were used to drive extinctions, yet divergent predictions when different measures of function were used. The inclusion of information on network structure had little apparent effect on the qualitative relationship between diversity and function. These results contribute to our growing understanding of the functional consequences of biodiversity from real systems and underscore the importance of species traits and realistic functional metrics to assessments of the ecosystem impacts of network degradation through species loss.
authors.affiliation: Department of Biology Swarthmore College Swarthmore Pennsylvania 19081; Department of Ecology University of São Paulo Sao Paulo 05508-090 Brazil.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Nichols
authors.affiliation: School of Environmental Sciences University of East Anglia Norwich Research Park Norwich NR47TJ U.K.
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Peres
authors.affiliation: School of Environmental Sciences University of East Anglia Norwich Research Park Norwich NR47TJ U.K; Animal and Environment Research Group Department of Life Sciences Anglia Ruskin University East Road Cambridge CB1 1PT U.K.
authors.forename: Joseph E
authors.initials: JE
authors.lastname: Hawes
authors.affiliation: Department of Ecology, Evolution and Environmental Biology Columbia University New York New York 10027.
authors.forename: Shahid
authors.initials: S
authors.lastname: Naeem
keywords: Biodiversity–ecosystem function; coextinction; dung beetles; fecal detritus; food webs; interaction networks; mammals; node loss; trophic interaction; tropical forest