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Subsidies mediate interactions between communities across space


Gounand, Isabelle; Harvey, Eric; Ganesanandamoorthy, Pravin; Altermatt, Florian (2017). Subsidies mediate interactions between communities across space. Oikos, 126(7):972-979.

Abstract

Most spatial ecology focuses on how species dispersal a ects community dynamics and coexistence. Ecosystems, however, are also commonly connected by ows of resources. We experimentally tested how neighbouring communities indirectly in uence each other in absence of dispersal, via resource exchanges. Using two-patch microcosm meta-ecosystems, we manipulated community composition and dynamics, by varying separately species key functional traits (autotroph versus heterotroph species and size of consumer species) and trophic structure of aquatic communities (species growing alone or in presence of competitors or predators). We then analysed the e ects of species functional traits and trophic structure on communities connected through spatial subsidies in the absence of actual dispersal. Both functional traits and trophic structure strongly a ected dynamics across neighbouring communities. Heterotroph communities connected to autotroph neighbours developed better than with heterotroph neighbours, such that coexistence of competitors was determined by the functional traits of the neighbouring community. Densities in autotroph communities were also strikingly higher when receiving subsidies from heterotroph communities compared to their own subsidies when grown in isolated ecosystems. In contrast, communities connected to predator-dominated ecosystems collapsed, without any direct contact with the predators. Our results demonstrate that because community composition and structure modify the distribution of biomass within a community, they may also a ect communities connected through subsidies through quantitative and qualitative changes of detritus ows. is stresses that ecosystem management should account for such interdependencies mediated by spatial subsidies, given that local community alterations cascade across space onto other ecosystems even if species dispersal is completely absent.

Abstract

Most spatial ecology focuses on how species dispersal a ects community dynamics and coexistence. Ecosystems, however, are also commonly connected by ows of resources. We experimentally tested how neighbouring communities indirectly in uence each other in absence of dispersal, via resource exchanges. Using two-patch microcosm meta-ecosystems, we manipulated community composition and dynamics, by varying separately species key functional traits (autotroph versus heterotroph species and size of consumer species) and trophic structure of aquatic communities (species growing alone or in presence of competitors or predators). We then analysed the e ects of species functional traits and trophic structure on communities connected through spatial subsidies in the absence of actual dispersal. Both functional traits and trophic structure strongly a ected dynamics across neighbouring communities. Heterotroph communities connected to autotroph neighbours developed better than with heterotroph neighbours, such that coexistence of competitors was determined by the functional traits of the neighbouring community. Densities in autotroph communities were also strikingly higher when receiving subsidies from heterotroph communities compared to their own subsidies when grown in isolated ecosystems. In contrast, communities connected to predator-dominated ecosystems collapsed, without any direct contact with the predators. Our results demonstrate that because community composition and structure modify the distribution of biomass within a community, they may also a ect communities connected through subsidies through quantitative and qualitative changes of detritus ows. is stresses that ecosystem management should account for such interdependencies mediated by spatial subsidies, given that local community alterations cascade across space onto other ecosystems even if species dispersal is completely absent.

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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:3 July 2017
Deposited On:11 Sep 2017 15:22
Last Modified:12 Sep 2017 07:58
Publisher:Wiley-Blackwell Publishing, Inc.
ISSN:0030-1299
Funders:This work was supported by the Swiss National Science Foundation Grant PP00P3_150698, University of Zurich and Eawag.
Additional Information:This is the peer reviewed version of the following article: Gounand, I., Harvey, E., Ganesanandamoorthy, P. and Altermatt, F. (2017), Subsidies mediate interactions between communities across space. Oikos, 126: 972–979. which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1111/oik.03922/full
Publisher DOI:https://doi.org/10.1111/oik.03922

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Embargo till: 2018-07-03