TY - JOUR
T1 - An experimental test of how parasites of predators can influence trophic cascades and ecosystem functioning
AU - Anaya-Rojas, Jaime M.
AU - Best, Rebecca J.
AU - Brunner, Franziska S.
AU - Eizaguirre, Christophe
AU - Leal, Miguel Costa
AU - Melián, Carlos J.
AU - Seehausen, Ole
AU - Matthews, Blake
N1 - Funding Information:
We thank D. Steiner, D. Hohmann, A. Taverna, M. Lürig, G. Antoniazza, L. Catalano, J. Naef, and B. Kienholz for their assistance in the lab, in the mesocosm garden, and in the field. We are very grateful for the support of the whole EAWAG Kastanienbaum community, especially to David Marquez, Kay Lucek, M. McGee, and two anonymous reviewers for their comments. This project was funded through the Lead Agency Project of the German Science Foundation (DFG, EI841/4-1) and the Swiss National Science Foundation (SNSF 139326) to CE and BM. The project was enabled by the stickleback cluster of the DFG priority program 1399 “Host–Parasite Co-evolution” and supported by a DFG grant to CE (EI 841/6-1). JMA-R analyzed the data and wrote the first drafts of the manuscript. JMA-R, RJB, and FSB performed the experiment. MCL contributed to data collection and writing the manuscript. JMA-R, RJB, BM, CE, and OS conceived the experiment and contributed substantially to the revisions of the manuscript. CJM made substantial contributions to the model construction, structure and revisions of the manuscript draft. Here we confirm that we do not have any conflict of interest.
Publisher Copyright:
© 2019 by the Ecological Society of America
PY - 2019/8
Y1 - 2019/8
N2 - Parasites can shape the structure and function of ecosystems by influencing both the density and traits of their hosts. Such changes in ecosystems are particularly likely when the host is a predator that mediates the dynamics of trophic cascades. Here, we experimentally tested how parasite load of a small predatory fish, the threespine stickleback, can affect the occurrence and strength of trophic cascades and ecosystem functioning. In a factorial mesocosm experiment, we manipulated the density of stickleback (low vs. high), and the level of parasite load (natural vs. reduced). In addition, we used two stickleback populations from different lineages: an eastern European lineage with a more pelagic phenotype (Lake Constance) and a western European lineage with a more benthic phenotype (Lake Geneva). We found that stickleback caused trophic cascades in the pelagic but not the benthic food chain. Evidence for pelagic trophic cascades was stronger in treatments where parasite load of stickleback was reduced with an antihelmintic medication, and where fish originated from Lake Constance (i.e., the more pelagic lineage). A structural equation model revealed that differences in stickleback lineage and parasite load were most likely to impact trophic cascades via changes in the composition, rather than overall biomass, of zooplankton communities. Overall, our results provide experimental evidence that parasites of predators can influence the cascading effects of fish on lower trophic levels with consequences on ecosystem functioning.
AB - Parasites can shape the structure and function of ecosystems by influencing both the density and traits of their hosts. Such changes in ecosystems are particularly likely when the host is a predator that mediates the dynamics of trophic cascades. Here, we experimentally tested how parasite load of a small predatory fish, the threespine stickleback, can affect the occurrence and strength of trophic cascades and ecosystem functioning. In a factorial mesocosm experiment, we manipulated the density of stickleback (low vs. high), and the level of parasite load (natural vs. reduced). In addition, we used two stickleback populations from different lineages: an eastern European lineage with a more pelagic phenotype (Lake Constance) and a western European lineage with a more benthic phenotype (Lake Geneva). We found that stickleback caused trophic cascades in the pelagic but not the benthic food chain. Evidence for pelagic trophic cascades was stronger in treatments where parasite load of stickleback was reduced with an antihelmintic medication, and where fish originated from Lake Constance (i.e., the more pelagic lineage). A structural equation model revealed that differences in stickleback lineage and parasite load were most likely to impact trophic cascades via changes in the composition, rather than overall biomass, of zooplankton communities. Overall, our results provide experimental evidence that parasites of predators can influence the cascading effects of fish on lower trophic levels with consequences on ecosystem functioning.
KW - density-mediated interactions
KW - ecosystem functioning
KW - mesocosms
KW - parasites
KW - stickleback
KW - structural equation models
KW - trait-mediated interactions
KW - trophic cascades
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U2 - 10.1002/ecy.2744
DO - 10.1002/ecy.2744
M3 - Article
C2 - 31135996
AN - SCOPUS:85070848993
SN - 0012-9658
VL - 100
JO - Ecology
JF - Ecology
IS - 8
M1 - e02744
ER -