Date of Award

Spring 2023

Degree Name

Bachelor of Science

Major

Biology

First Advisor

Benjamin Toscano

Second Advisor

Daniel Balckburn

Third Advisor

Abigail Maley

Abstract

Predators affect prey communities through two pathways: by eating prey (i.e., consumptive effects) and by modifying prey traits (i.e., non-consumptive effects), such as behavior. Predator body size could influence both consumptive and non-consumptive effects, but these effects have rarely been compared across predator sizes. Using a field experiment, I manipulated stonefly (Acroneuria abnormis) size and their ability to feed on prey (via mouthpart gluing) and measured effects on the aquatic insect prey community in the Tankerhoosen River (Vernon, Conn.). Field cages retained stonefly predators but allowed mobile prey to emigrate. I found that the presence of stoneflies reduced total prey abundance, but stonefly size and mouthpart gluing had no additional effect on prey abundance. The same was true when different insect prey orders (Trichoptera, Diptera, Ephemeroptera, Plecoptera) and different insect prey taxa (Hydropsychidae hydropsyche, Chironomidae, Dolophilodes distinctus) were considered separately. The one exception to this pattern was that an immobile prey, Glossoma, was weakly affected by the presence of stoneflies, likely because this genus was unable to emigrate from field cages. The finding that stoneflies still reduce prey abundance even when they cannot feed suggests that non-consumptive effects dominate in this system. Additionally, my experimental design allowed me to conclude that non-consumptive effects do not depend on stonefly size per se, but rather are based solely on total stonefly predator biomass. My future work will explore whether the effects of stonefly size and mouthpart gluing emerge when considering different size classes of prey.

Comments

Senior Thesis completed at Trinity College, Hartford CT for the degree of Bachelor of Science in Biology.

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