Date of Award

2012

Document Type

Thesis

Degree Name

Master of Environmental Studies (MES)

First Advisor

Paul Rothrock

Second Advisor

Robert Reber

Third Advisor

Richard Dunbar, Jr.

Abstract

Lythrum salicaria is an invasive wetland hydrophyte native to Eurasia. Since 1814, it has been spreading throughout North America and has been in Indiana since 1900. A wide variety of negative ecosystem impacts have been documented but some authors have questioned these findings. Galerucella spp. have been utilized as biological control agents for Lythrum salicaria in Indiana since 1994, but this is the first publication to examine insect control in the state. Studies from other states have generally been shorter time frames than the eight to ten years of this study. This study examined the impacts of Galerucella spp. at four Indiana wetlands by considering changes in beetle abundance, plant species richness, Lythrum salicaria cover, flowering, and stem densities over time. These relationships were analyzed using Spearman’s rank-sum correlations. Galerucella spp. abundance was significantly correlated at two sites, species richness and percent cover were both significantly correlated at three sites, and number of inflorescence and stem density were significant at all four sites. The number of inflorescence show the strongest correlation, with ρ’s between -0.4575 and -0.7761. Overall, it was determined that following the introduction of Galerucella spp. Lythrum salicaria had a significant negative response at each of the wetlands. Variation was observed between sites, but their impacts at these wetlands strongly suggest that Galerucella spp. can play a major role in controlling Lythrum salicaria.

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