Assessing multiple predator, diurnal and search area effects on predatory impacts by ephemeral wetland specialist copepods

Ross N Cuthbert,Tatenda Dalu,Olaf L F Weyl,Amanda Callaghan,Ryan J Wasserman,Cristián J Monaco,Jaimie T A Dick

doi:10.1007/s10452-019-09735-y

Abstract

Predator–prey interaction strengths can be highly context-dependent. In particular, multiple predator effects (MPEs), variations in predator sex and physical habitat characteristics may affect prey consumption rates and thus the persistence of lower trophic groups. Ephemeral wetlands are transient ecosystems in which predatory copepods can be numerically dominant. We examine the interaction strengths of a specialist copepod Paradiaptomus lamellatus towards mosquito prey in the presence of conspecifics using a functional response approach. Further, we examine sex variability in predation rates of P. lamellatus under circadian and surface area variations. Then, we assess the influence of a co-occurring heterospecific predatory copepod, Lovenula raynerae, on total predation rates. We demonstrate MPEs on consumption, with antagonism between conspecific P. lamellatus predatory units evident, irrespective of prey density. Furthermore, we show differences between sexes in interaction strengths, with female P. lamellatus significantly more voracious than males, irrespective of time of day and experimental arena surface area. Predation rates by P. lamellatus were significantly lower than the heterospecific calanoid copepod L. raynerae, whilst heterospecific copepod groups exhibited the greatest predatory impact. Our results provide insights into the predation dynamics by specialist copepods, wherein species density, diversity and sex affect interaction strengths. In turn, this may influence population-level persistence of lower trophic groups under shifting copepod predator composition.

Highlights

Predation is a fundamental biotic process which profoundly affects ecosystem structure, stability and functioning (Brooks and Dodson 1965; Paine 1980; Wasserman and Froneman 2013)
We examined the predatory impacts of P. lamellatus in the presence of L. raynerae by quantifying predation in single (i.e. 1 P. lamellatus or 1 L. raynerae separately) and mixed groups (i.e. 1 of each species in combination)
Antagonistic multiple predator effects were evidenced by interacting conspecific P. lamellatus irrespective of prey density

Summary

Introduction

Predation is a fundamental biotic process which profoundly affects ecosystem structure, stability and functioning (Brooks and Dodson 1965; Paine 1980; Wasserman and Froneman 2013). Models applied to consumer–resource systems classically assumed functional equivalence of predators within populations (Volterra 1928; Lotka 1956; Rosenzweig and MacArthur 1963), limiting comprehensive quantifications of interaction strengths under shifting biotic contexts (e.g. predator sex or ontogenic stage). Given that most ecological communities include multiple predators which share common resources, predator–predator exchanges can profoundly alter interaction strengths (Soluk 1993; Sih et al 1998; Bolker et al 2003; Wasserman et al 2016c). One classical ecological approach to quantify consumer–resource (e.g. predator–prey) interactions under context dependencies is through

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Conclusion