The effects of food web structure on ecosystem function exceeds those of precipitation.
Ecosystems are being stressed by climate change, but few studies have tested food web responses to changes in precipitation patterns and the consequences to ecosystem function. Fewer still have considered whether results from one geographic region can be applied to other regions, given the degree of community change over large biogeographic gradients. We assembled, in one field site, three types of macroinvertebrate communities within water-filled bromeliads. Two represented food webs containing both a fast filter feeder-microbial and slow detritivore energy channels found in Costa Rica and Puerto Rico, and one represented the structurally simpler food webs in French Guiana, which only contained the fast filter feeder-microbial channel. We manipulated the amount and distribution of rain entering bromeliads and examined how food web structure mediated ecosystem responses to changes in the quantity and temporal distribution of precipitation. Food web structure affected the survival of functional groups in general and ecosystem functions such as decomposition and the production of fine particulate organic matter. Ecosystem processes were more affected by decreased precipitation than were the abundance of micro-organisms and metazoans. In our experiments, the sensitivity of the ecosystem to precipitation change was primarily revealed in the food web dominated by the single filter feeder-microbial channel because other top-down and bottom-up processes were weak or absent. Our results show stronger effects of food web structure than precipitation change per se on the functioning of bromeliad ecosystems. Consequently, we predict that ecosystem function in bromeliads throughout the Americas will be more sensitive to changes in the distribution of species, rather than to the direct effects caused by changes in precipitation.
Laboratoire Ecologie Fonctionnelle et Environnement (ECOLAB), INP, UPS, Université de Toulouse, 31062, Toulouse, France.|ECOLAB (UMR-CNRS 5245), CNRS, 118 Route de Narbonne, 31062, Toulouse, France.
M Kurtis
MK
Trzcinski
Department of Zoology, University of British Columbia, #2370-6240 University Blvd., Vancouver, BC V6T 1Z4, Canada.
Diane S
DS
Srivastava
Université Blaise Pascal, Université Clermont Auvergne, BP 10448, 63000, Clermont-Ferrand, France.|Laboratoire Microorganismes: Génome et Environnement (UMR-CNRS 6023), CNRS, 63177, Aubière, France.
Bruno
B
Corbara
Écologie des Forêts de Guyane (UMR 8172), Campus Agronomique, 97379, Kourou Cedex, France.
Olivier
O
Dézerald
Boulevard de la Lironde, IRD, botAnique et bioinforMatique de l'Architecture des Plantes (UMR-IRD 123), TA A-51/PS2, 34398, Montpellier Cedex 5, France.
Céline
C
Leroy
Université Blaise Pascal, Université Clermont Auvergne, BP 10448, 63000, Clermont-Ferrand, France.|Laboratoire Microorganismes: Génome et Environnement (UMR-CNRS 6023), CNRS, 63177, Aubière, France.
Jean-François
JF
Carrias
Laboratoire Ecologie Fonctionnelle et Environnement (ECOLAB), INP, UPS, Université de Toulouse, 31062, Toulouse, France.|ECOLAB (UMR-CNRS 5245), CNRS, 118 Route de Narbonne, 31062, Toulouse, France.
Alain
A
Dejean
Laboratoire Ecologie Fonctionnelle et Environnement (ECOLAB), INP, UPS, Université de Toulouse, 31062, Toulouse, France.|ECOLAB (UMR-CNRS 5245), CNRS, 118 Route de Narbonne, 31062, Toulouse, France.
Régis
R
Céréghino
D000818:Animals; D059001:Aquatic Organisms / Q000502:physiology*; D031229:Bromeliaceae / Q000254:growth & development; D003364:Costa Rica; D055864:Droughts; D017753:Ecosystem; D020387:Food Chain; D005616:French Guiana; D011235:Predatory Behavior; D011647:Puerto Rico; D011891:Rain
French Guiana; bromeliad; climate change; community interactions; drought; ecosystem function; invertebrates; micro-organisms; phytotelmata; precipitation