Advisor(s)

Geoffrey C. Trussell

Contributor(s)

Salvatore J. Genovese, Philip O. Yund

Date of Award

2009

Date Accepted

8-2009

Degree Grantor

Northeastern University

Degree Level

M.S.

Degree Name

Master of Science

Department or Academic Unit

College of Arts and Sciences. Department of Biology.

Keywords

injury, non-consumptive, predator-prey, prey state, shell, trait-mediated

Subject Categories

Ecosystem management, Predatory animals--Ecology

Disciplines

Medical Sciences

Abstract

Non-consumptive effects exerted by predators on their prey can have far reaching implications for the structure of ecological communities and functioning of ecosystems. In addition to risk cues detected from nearby predators, physiological state of individual prey animals may influence the sign and magnitude of trait-mediated indirect interactions. Using a tri-trophic intertidal food web, I tested the influence of prey state as represented by injury history on behavior and resource allocation in an intermediate prey species, the marine snail Nucella lapillus. Despite the presence of shell injury in natural populations of this and other intertidal gastropods, injured N. lapillus showed no differences in feeding rate, energy assimilation efficiency or growth in morphological traits relative to uninjured conspecifics. I also compared the relative influence of predator risk cue and prey physiological state on the combined indirect effect of predators in this system. Predation risk cues account for the great majority of reductions in resource and energy consumption while physiological prey state has negligible influence. Although repaired shells were significantly weaker when tested in compression than uninjured shells, injury status did not influence mortality in snails exposed to predation in the field. These data indicate that predation risk is a major driver of resource consumption and community effects while prey state as represented by shell injury makes little contribution.

Document Type

Master's Thesis

Rights Holder

Timothy Robert Dwyer


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