Undergraduate Honors Theses

Thesis Defended

Spring 2016

Document Type

Thesis

Type of Thesis

Departmental Honors

Department

Ecology and Evolutionary Biology

First Advisor

Dr. Michael Breed

Second Advisor

Dr. Pieter Johnson

Third Advisor

Dr. Peter Newton

Abstract

Plant diversity is declining due to anthropogenic land use change. Associated insects must respond to these altered environmental conditions; however, the effect of this decline on movement patterns of terrestrial arthropods is largely unknown. As top predators in arthropod communities, carabid beetles (Coleoptera: Caribidae) play a key role in ecosystem functioning and serve as biological pest control agents. Knowledge about carabid’s movement such as dispersal patterns and food search behavior is crucial for understanding how this beetle perceives and responds to environmental factors. Experimental plant communities of a grassland biodiversity experiment were used to observe two common ground beetles, Pterostichus melanarius and Harpalus rufipes, on a microhabitat scale along a gradient of manipulated plant species richness and functional diversity. Fluorescent paint, which glows under ultraviolet light, facilitated observations of the nocturnal beetles. Beetle traces were recorded by hand and digitalized to analyze length travelled, dislocation, number of turns and step length. Additionally, pitfall trapping was used to assess recapture time. Results show that P. melanarius and H. rufipes respond to different aspects of vegetation—the lower the plant species richness, the more likely beetles will be moving. For H. rufipes, there were smaller scale movements in areas with higher functional diversity. Species and sex also played a role in determining movement patterns. Males travelled the furthest distance in both species. However, recapture rates differed by species with P. melanarius recaptured at a higher rate than H. rufipes. A novel observation method combined with traditional pitfall trapping gives a more complete picture of beetle movement and activity, furthering knowledge of beetle movement applicable to agricultural management plans.

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