Degree Type

Dissertation

Date of Award

2019

Degree Name

Doctor of Philosophy

Department

Ecology, Evolution, and Organismal Biology

Major

Ecology and Evolutionary Biology; Entomology

First Advisor

Amy L. Toth

Second Advisor

Matthew E. O'Neal

Abstract

Wild bee and managed honey bee populations are declining across the U.S., with populations particularly at risk in the Upper Midwest where vast areas of land have been converted into extensive row-crop agricultural systems, resulting in homogenous landscapes with reduced forage availability. These declines are problematic as wild bees are an essential part of maintaining natural ecosystems, and honey bees contribute to pollination of over 150 crops. The state of Iowa has been identified as a critical area for pollinator conservation and is an ideal location to study agriculture-related bee declines. This area represents a model landscape for other parts of the world, can be used to understand how bees respond to agricultural intensification, and may provide valuable insights into the future of pollinator health. For my doctoral dissertation research, I examined the responses of both wild and managed bees to row-crop agriculture, by investigating population, colony, and individual metrics of health both longitudinally over time and spatially, across landscapes with different extents of agricultural industrialization. In addition, I explored two ways in which landscape diversity may help to mitigate bee health declines in monoculture crop landscapes: diversified fruit and vegetable farming, and native perennial prairie habitat. Overall, I found that landscape diversity, not honey bee presence, positively influences the wild bee community. In contrast, managed honey bees had a positive response to row-crop agriculture with higher populations and colony health in landscapes with more production of corn and soybean; however, these colonies ultimately declined in the late season, i.e., post-crop senescence. Diversified farming through fruit and vegetable production resulted in small increases abundance and richness of a subset of the wild bee community during parts of the season. Honey bee colony and individual bees were healthier on fruit and vegetable farms compared to monocrop soybeans; however, honey bees still declined in the late season. Native perennial prairie habitat was able to mitigate late season honey bee declines and may be a promising habitat type able to support both wild and managed bees in heavily cultivated row-crop agricultural systems. These studies underline the importance of landscape and farm diversity in supporting the health of both managed and wild bees.

Copyright Owner

Ashley Louise St. Clair

Language

en

File Format

application/pdf

File Size

192 pages

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