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Volume 102, Issue 12 e03534
Article

Predator complementarity dampens variability of phytoplankton biomass in a diversity-stability trophic cascade

Chase J. Rakowski

Corresponding Author

Chase J. Rakowski

Department of Integrative Biology, University of Texas at Austin, Austin, Texas, 78712 USA

E-mail: [email protected]

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Caroline E. Farrior

Caroline E. Farrior

Department of Integrative Biology, University of Texas at Austin, Austin, Texas, 78712 USA

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Schonna R. Manning

Schonna R. Manning

Department of Molecular Biosciences, University of Texas at Austin, Austin, Texas, 78712 USA

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Mathew A. Leibold

Mathew A. Leibold

Department of Biology, University of Florida, Gainesville, Florida, 32611 USA

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First published: 08 September 2021
Citations: 4

Corresponding Editor: Shelley E. Arnott.

Abstract

Trophic cascades – indirect effects of predators that propagate down through food webs – have been extensively documented in many ecosystem types. It has also been shown that predator diversity can mediate these trophic cascades and, separately, that herbivore biomass can influence the stability of primary producers. However, whether predator diversity can cause cascading effects on the stability of lower trophic levels has not yet been studied. We conducted a laboratory microcosm experiment and a field mesocosm experiment manipulating the presence and coexistence of two heteropteran predators and measuring their effects on zooplankton herbivores and phytoplankton basal resources. We predicted that if the predators partitioned their zooplankton prey, for example by size, then the co-presence of the predators would reduce zooplankton prey mass and lead to (1) increased biomass of, and (2) decreased temporal variability of phytoplankton basal resources. We present evidence that the predators partitioned their zooplankton prey, leading to a synergistic suppression of zooplankton. In turn, this enhanced zooplankton suppression led to only a weak, non-significant increase in the central tendency of phytoplankton biomass, but significantly reduced its variability. Our results demonstrate that predator diversity may indirectly stabilize basal resource biomass via a “diversity-stability trophic cascade,” seemingly dependent on predator complementarity, even when there is no significant classic trophic cascade altering the central tendency of biomass. Therefore predator diversity, especially if correlated with diversity of prey use, could play a role in regulating ecosystem stability. This link between predator diversity and producer stability has implications for conservation and for potential biological control methods to improve crop yield reliability.

Open Research

Data (Rakowski et al. 2021) are available in the Dryad repository: https://doi.org/10.5061/dryad.kd51c5b67.