Functional responses of the intertidal amphipod Echinogammarus marinus: effects of prey supply, model selection and habitat complexity

Abstract

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 468:191-202 (2012) - DOI: https://doi.org/10.3354/meps09978 Functional responses of the intertidal amphipod Echinogammarus marinus: effects of prey supply, model selection and habitat complexity Mhairi E. Alexander1,*, Jaimie T. A. Dick1, Nessa E. O’Connor1, Neal R. Haddaway2, Keith D. Farnsworth1 1School of Biological Sciences, Queen’s University Belfast, MBC, 97 Lisburn Road, Belfast BT9 7BL, UK 2School of Ocean Sciences, Bangor University, Menai Bridge, Anglesey LL59 5AB, UK *Email: malexander06@qub.ac.uk ABSTRACT: The influence of predation in structuring ecological communities can be informed by examining the shape and magnitude of the functional response of predators towards prey. We derived functional responses of the ubiquitous intertidal amphipod Echinogammarus marinus towards one of its preferred prey species, the isopod Jaera nordmanni. First, we examined the form of the functional response where prey were replaced following consumption, as compared to the usual experimental design where prey density in each replicate is allowed to deplete. E. marinus exhibited Type II functional responses, i.e. inversely density-dependent predation of J. nordmanni that increased linearly with prey availability at low densities, but decreased with further prey supply. In both prey replacement and non-replacement experiments, handling times and maximum feeding rates were similar. The non-replacement design underestimated attack rates compared to when prey were replaced. We then compared the use of Holling’s disc equation (assuming constant prey density) with the more appropriate Rogers’ random predator equation (accounting for prey depletion) using the prey non-replacement data. Rogers’ equation returned significantly greater attack rates but lower maximum feeding rates, indicating that model choice has significant implications for parameter estimates. We then manipulated habitat complexity and found significantly reduced predation by the amphipod in complex as opposed to simple habitat structure. Further, the functional response changed from a Type II in simple habitats to a sigmoidal, density-dependent Type III response in complex habitats, which may impart stability on the predator−prey interaction. Enhanced habitat complexity returned significantly lower attack rates, higher handling times and lower maximum feeding rates. These findings illustrate the sensitivity of the functional response to variations in prey supply, model selection and habitat complexity and, further, that E. marinus could potentially determine the local exclusion and persistence of prey through habitat-mediated changes in its predatory functional responses. KEY WORDS: Functional response · Predation · Prey replacement · Habitat complexity · Marine amphipod Full text in pdf format PreviousNextCite this article as: Alexander ME, Dick JTA, O’Connor NE, Haddaway NR, Farnsworth KD (2012) Functional responses of the intertidal amphipod Echinogammarus marinus: effects of prey supply, model selection and habitat complexity. Mar Ecol Prog Ser 468:191-202. https://doi.org/10.3354/meps09978 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 468. Online publication date: November 14, 2012 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2012 Inter-Research.