Date on Master's Thesis/Doctoral Dissertation

5-2021

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Biology

Degree Program

Biology, PhD

Committee Chair

Eason, Perri

Committee Co-Chair (if applicable)

Carreiro, Margaret

Committee Member

Carreiro, Margaret

Committee Member

Alexander, James

Committee Member

Cobbs, Gary

Committee Member

Rieske-Kinney, Lynne

Author's Keywords

urban garden; urban conservation; butterfly garden; butterfly behavior; model caterpillar

Abstract

Butterfly populations are declining, and habitat degradation due to urbanization is a major contributing factor. Gardens represent a large proportion of land area in many cities, and thus may be important for conserving butterflies in urban environments. In this dissertation, I examine how garden features (ex: size, level of urbanization, plant diversity) affect adult butterfly diversity/abundance, behavior, and the predation risk faced by caterpillars. My study sites were native plant gardens in Jefferson, Bullitt, and Hardin Cos.,KY. In Chapter One, I used clay caterpillars to assess differences in predation pressure in gardens along a gradient of percent impervious surface (%IS). I glued clay caterpillars to plant leaves at 24 gardens in both July and October 2017, then assessed them for damage. 97% of damage was attributable to parasitoid wasps, spiders, ants, vertebrates, and predatory wasps. Overall attack rate declined significantly with increasing %IS and plant species richness (plantR). The attack rate by each predator type responded differently to %IS and plant biovolume density (BVD). In Chapter Two, I surveyed adult butterflies at 26 gardens from May–October 2018, to evaluate how garden characteristics influence butterfly diversity and abundance. Butterfly species richness (BSR) significantly increased as garden size increased. BSR was also affected by an interaction between %IS and plantR. BSR increased with increasing plantR, and this effect was stronger when %IS was high. Butterfly abundance was affected by multiple interactions, including %IS with garden area, and %IS with BVD. Butterfly abundance increased with increasing garden size and BVD, particularly when %IS was high. The proportion of larval host-specialist species I recorded declined as %IS, but increased when both garden size and plantR increased together. In Chapter Three, I recorded the flight/feeding behaviors of cabbage white butterflies (Pieris rapae) to determine if urbanization affects butterfly behavior. I conducted behavioral trials at 6 urban and 6 rural gardens in July-October 2019. Butterflies released in urban gardens spent more time actively flying and/or feeding from flowers than butterflies in rural gardens. They also flew more tight turns, even when they did not feed from flowers, indicating more intensive searching behavior in urban gardens.

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