Date of Graduation

7-2020

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Biology (PhD)

Degree Level

Graduate

Department

Biological Sciences

Advisor/Mentor

Willson, John D.

Committee Member

Beaupre, Steven J.

Second Committee Member

Magoulick, Daniel D.

Third Committee Member

Briggler, Jeffrey T.

Keywords

agriculture; density-dependence; grasslands; occupancy modeling; prairies; prescribed fire

Abstract

The Crawfish Frog (Lithobates areolatus) is an imperiled amphibian currently experiencing severe declines across its range. As a species with unique habitat requirements that is threatened by habitat loss, understanding their status across the landscape and how they respond to environmental stressors is key to developing effective conservation strategies that maintain and expand viable populations. We used a combination of observational, experimental, and theoretical approaches to understand the status of Crawfish Frog populations in Northwest Arkansas (NWA), their individual and population-level response to human-induced changes in vegetation surrounding breeding wetlands, and the effects of fire management on larval development within breeding wetlands. Specifically, in Chapter 1, we performed a landscape-level assessment of Crawfish Frog status at 81 sites across NWA. Crawfish Frog occupancy was relatively low (~26%), but occupancy probability increased strongly with density of prairie mounds, a proxy for habitat quality, and modestly with prevalence of clay/gravelly silt loam soils. In Chapters 2 and 3, we performed a series of mesocosm experiments to investigate how vegetation (Native Prairie or Non-Native Tall-Fescue Grass) surrounding wetlands interacted with timing of oviposition and density-dependence to affect larval amphibian development. We found that Fescue-dominated wetlands might act as ecological traps resulting in complete reproductive failure of breeding Crawfish Frogs within a season, due to higher microbial respiration. Demographic population revealed that populations breeding in Fescue-dominated wetlands had a more variable population size and had a 100-500% higher probability of quasi-extinction within 200 years, compared to populations breeding in prairie-dominated wetlands. Finally, we performed an experiment to measure the effect of ash-deposition and reduced vegetation due to fire on larval Crawfish Frog development. Our results suggested that the quantity of ash used in our experiment had negligible effects on the development of aquatic amphibian larvae, but reduction of vegetation biomass by fire results in lower survival and biomass production if burning occurs during the dormant season, prior to wetlands filling. Collectively, our results indicate that Crawfish Frogs need high quality natural prairie habitat for population persistence and although relict populations exist in agricultural landscapes, these are poor replacements for natural grasslands.

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