Date of Graduation

12-2023

Document Type

Thesis

Degree Name

Master of Science in Biology (MS)

Degree Level

Graduate

Department

Biological Sciences

Advisor/Mentor

Michelle A. Evans-White

Committee Member

Magoulick, Daniel

Second Committee Member

Naithani, Kusum

Third Committee Member

Savin, Mary

Keywords

conservation, freshwater ecology, macroinvertebrates, stream ecology

Abstract

Freshwater ecosystems are facing a crisis with extinction rates of aquatic species exceeding those of their terrestrial counterparts by up to fivefold. This decline is predominantly attributed to evolving land use patterns within watersheds, leading to chemical and physical transformations in freshwater habitats. Northwest Arkansas (NWA) represents one of the fastest-growing regions in the United States, undergoing substantial shifts in land use. Consequently, the status of aquatic life in this region remains uncertain. Addressing this concern, the latest Arkansas Wildlife Action Plan emphasizes the necessity of distribution and population data to guide conservation efforts for Species of Greatest Conservation Need (SGCN). Among these species are three Allocapnia stonefly species—A. jeanae, A. ozarkana, and A. warreni—historically found in NWA during their winter emergence periods. In this study, I conducted an analysis combining fine-scale, site-specific surveys, and species-specific assessments to provide insights into the presence and richness of Allocapnia along three major river systems in NWA: the White River, Clear Creek, and West Fork White River. To inform my analyses, I utilized historical stonefly surveys conducted 50 and 30 years ago. I conducted Allocapnia surveys at 22 sites during winter emergence periods in 2020-2021 and 2021-2022, with an average of 10 visits per site. Specimens were collected from emergent structures and identified in the laboratory. To gain an understanding of the relationships between independent variables (including land use, latitude, draining area, and Strahler stream order) and the presence of each Allocapnia species, I employed orthogonal partial least square regression. Additionally, univariate threshold analyses were conducted to pinpoint critical points in land use values that resulted in significant declines in Allocapnia richness. My findings reveal that Allocapnia were predominantly found in forested streams, with no occurrences recorded at highly urbanized sampling sites. Notably, A. rickeri and A. mohri displayed high prevalence and abundance in large, high-order sections within the West Fork White River basin, suggesting a greater resilience to land use changes compared to other Allocapnia species. Allocapnia jeanae demonstrated successful dispersion within the NWA landscape over the past five decades, albeit primarily restricted to tributaries, with limited occurrences within the mainstem of sampled rivers. Allocapnia ozarkana, although persisting, were collected in low numbers. Allocapnia warreni was not detected in Clear Creek and has not been recorded in this area for over half a century, indicating a likely extirpation. Land use thresholds were identified at 64.3% (±25.17) for forest, 26.19% (±5.18) for agriculture, 8.56% (±0.74) for urban, and 1.51% (±0.16) for impervious surface cover. These thresholds highlight the critical importance of concentrating conservation efforts on the protection of forested headwaters to ensure the preservation of vital habitats for aquatic shredding macroinvertebrates, such as Allocapnia. Additional actions in agricultural and urban areas should include the maintenance of riparian zones and stormwater management In the face of an evolving landscape, understanding the effects of land use on aquatic life remains imperative to safeguard our natural resources and ensure the sustainability of our ecosystems.

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