In the southeastern United States, ephemeral wetlands in pine flatwoods provide important habitat for amphibians and aquatic invertebrates, but extensive deforestation has destroyed or isolated many wetlands and fire suppression has altered vegetation in others. My goals were to identify how wetland hydroperiods have changed through time and to examine the effects of long-term fire suppression on aquatic communities, including Reticulated Flatwoods Salamanders (Ambystoma bishopi) and Ornate Chorus Frogs (Pseudacris ornata). Chapter 1 used a modeling approach to relate wetland hydroperiods to current climate conditions and to hindcast historic conditions. Over the past 118 years, hydroperiods were often unfavorable for A. bishopi reproduction, and in recent years hydroperiods were shortened by persistent drought. Chapters 2 and 3 focused on identifying the effects of shifting from an open, grass dominated wetland to a wetland with high canopy cover and little herbaceous vegetation. In Chapter 2, I quantified amphibian and invertebrate communities in several wetlands. A. bishopi and P. ornata tended to occupy wetlands with lower canopy cover and higher herbaceous vegetation cover. Aquatic invertebrate abundance was generally higher in wetlands with lower shrub density and lower canopy cover. In Chapter 3, I examined how a reduction in herbaceous vegetation affected tadpoles when a predatory crayfish was present using two experiments. Crayfish were effective predators of both species across all vegetation treatments and often caused nonlethal tail injury. My results suggest that managers should focus on ensuring that wetland basins regularly burn, and wetlands with longer hydroperiods should be a management priority. / Master of Science

The flatwoods ecosystem of Florida has been heavily depleted over time but remains one of the most important systems to many threatened and endangered species. Areas that have been converted into non-native pastures may be restored to provide not only this invaluable ecosystem but also restore connectivity of the surrounding ecosystems. The pasture areas on The Disney Wilderness Preserve in central Florida were surveyed, and a conceptual plan for restoration was written in 1996. That same year a pilot study was developed to assess five methods for removing non-native pasture grasses. The treatments studied were single herbicide, single disc, multiple herbicide, multiple disc, and single herbicide with two disc treatments. All plots were monitored once a year for three years along non-permanent transects. Percent cover was estimated for seven variables and a species list was developed for each plot. The triple herbicide treatment had the best overall success in removal of non-natives and establishment of native species characteristic of flatwoods communities. This treatment also had the highest species richness. The results of this study were used to develop the long term restoration plan for the remaining pasture areas of the preserve. This information may also be useful to restore pastures that connect other important ecosystems being purchased and protected throughout Florida and the Southeastern United States.

A significant acreage of poorly drained sites occurs in the Western Gulf region of the United States. These sites experience standing water through much of the winter and spring, resulting in poor seedling survival. In addition, the sites occasionally experience a summer drought that affects tree growth. This study was designed to determine the effects of intensive forest management on seedling growth and physiology, and to enhance seedling performance under these harsh conditions. Fertilization, chemical vegetation control and mechanical site preparation were used in different combinations to test the effects of these intensive forest management tools on seedling above- and below-ground growth, survival, water status, gas exchange attributes, and nutrient concentrations in the foliage and soil solution. Ten sites were established in southern Arkansas in 1998 and 1999 to monitor loblolly pine (Pinus taeda L.) seedling performance in three consecutive growing seasons between 1998 and 2000. Fertilization, chemical vegetation control and mechanical site preparation increased above-ground growth. Growth increment from mechanical site preparation was comparable to that from fertilization. Survival was not affected by any treatment. Fertilization enhanced root growth, more so in the shallow soil layers. Subsoil bulk density greatly restricted root growth, resulting in decreased above-ground growth. Chemical vegetation control made more soil water available to the seedlings during drought, resulting in increased seedling water potential. The effect of chemical vegetation control on seedling water potential was absent in the early growing season when soil moisture was abundant. Seedlings on plots treated with bedding-plus-fertilizer or bedding alone experienced stomatal closure at times of severe water stress while those treated with chemical vegetation control were able to continue net carbon dioxide assimilation. Fertilization did not increase needle nutrient concentrations, but increased needle weight, thereby increasing total nutrient content. Fertilization increased base cation concentrations in the soil solution, but had no effect on nitrogen and phosphorus concentrations. Intensive forest management was found to be a viable tool for optimum loblolly pine seedling growth and survival on poorly drained sites in the Western Gulf region of the United States.

The relationship of ant community composition to various habitat characteristics is compared across four habitat types and 12 environmental variables in Mississippi. The four habitat types include pasture, prairie, and oak-hickory forests in the Black Belt and forests in the Flatwoods physiographic region. Ants were sampled using pitfall traps, litter sampling, baiting and hand collecting. A total of 20,916 ants representing 68 species were collected. NMS and ANCOVA both revealed three distinct ant communities (pasture, prairie, and ?forests?) based on species composition and mean ant abundance per habitat type between the four habitat types. Principal component analysis (PCA) partitioned the 12 environmental variation into four axes with eigenvalues >1. Axis 1 differentiated open grass-dominated habitats from woodlands. In contrast axis two mainly separated pastures from prairie remnants. Multiple regression models using the four significant PCA axes revealed that total species richness was significantly affected by variation in the first two PCA axes. Forested sites supported approximately nine more species of ants than prairies and 21 more than pastures. Comparisons of the abundance of ant functional groups were also made between the four habitat types with multiple regression models to investigate how the environmental variables affected certain groups of ants. Annotated notes are included for each ant species encountered during this study.

The southeastern United States is a global biodiversity hotspot but has experienced severe declines of natural ecosystems. The southeast is currently facing widespread change, particularly from an increasing human population and climate change, that is likely to impact all remaining natural areas to some degree. In this work, I examine some of the challenges currently facing imperiled species of reptiles and amphibians in this region. The work is focused on two species, the Reticulated Flatwoods Salamander (Ambystoma bishopi) and the Eastern Indigo Snake (Drymarchon couperi) both of which are listed on the U.S. Endangered Species List. Chapter 1 used Light Detection and Ranging (LiDAR) data to measure wetland bathymetry (basin shape) in flatwoods salamander breeding wetlands. Bathymetry data were used to construct stage–area relationships for each wetland, and a history of water level monitoring data were applied to these relationships to build multi-year time series of flooded area metrics. These metrics were then combined with an assessment of vegetation characteristics to map potentially suitable habitat for flatwoods salamander breeding within each wetland. Chapter 2 focused on flatwoods salamander phenology (the timing of life history events) in response to climate change. I quantified flatwoods salamander movements into and out of breeding wetlands over a 10-year period (2010–2020), identifying temperature and precipitation patterns that were conducive to salamander movements. I then used future climate projections to forecast movement opportunities for flatwoods salamander from 2030–2099 and used an existing hydrologic model built on the same climate data to understand how phenology may interact with hydrology. Overall, only a small number of years are likely to have an ideal intersection of phenology and hydrology as has been observed during recent breeding seasons. Chapter 3 described the construction of a stochastic Integral Projection Model for flatwoods salamanders. I integrated the projections from Chapter 2 with the population model to estimate the viability of two flatwoods salamander populations from 2030–2099 under multiple climate change scenarios. The results indicated that approximately half of the examined scenarios resulted in a high probability (>0.5) of extinction when considering both wetland hydrology and salamander phenology. In Chapter 4, I described the creation of a stochastic Integral Projection Model for indigo snakes. I then demonstrated the utility of this model by examining the effects of initial population size, road density, and removal of individuals to support a captive colony on indigo snake populations. I found that high road densities and high collection rates would likely lead to population declines, although the rate of declines and extinction risk varied across scenarios. Taken together, these projects highlight some of the challenges currently facing herpetofauna in the southeastern United States, demonstrate the difficulty in conserving these often-overlooked species, and provide useful tools for ongoing conservation efforts focusing on these two imperiled species. / Doctor of Philosophy / We are in the midst of a global biodiversity crisis, with rates of species extinction far exceeding normal levels. Species loss is largely driven by global change attributable to human activities. A rapidly changing world can make it challenging to effectively conserve and manage imperiled species. In this work, I studied two species found only in the southeastern United States that are listed on the U.S. Endangered Species List. Chapters 1–3 focused on the Reticulated Flatwoods Salamander (Ambystoma bishopi), while Chapter 4 focused on the Eastern Indigo Snake (Drymarchon couperi). In Chapter 1, I used high resolution elevation data to map the shape of flatwoods salamander breeding wetlands. These data were then used to estimate flooded areas across multiple years. Flooded area metrics were combined with vegetation measurements to map potential flatwoods salamander breeding habitat. In Chapter 2, I examined how flatwoods salamander movements may respond to climate change. I identified time periods and weather conditions that coincided with flatwoods salamander movements into and out of breeding wetlands. I then projected potential movement opportunities based on multiple future climate scenarios for each breeding season from 2030–2099. My results showed that few years are likely to be ideal for flatwoods salamander reproduction, which is similar to trends observed in recent years. In Chapter 3, I built a population model for flatwoods salamanders. I then combined the model with predictions made in Chapter 2 to estimate the probability that populations would go extinct by the end of the century. The results indicated that the two flatwoods salamander populations examined had a high probability (>0.5) of extinction in about 50% of the climate scenarios. In Chapter 4, I constructed a population model for indigo snakes using a variety of available data. I used this model to examine the effects of road density, initial population size, and removal of individuals to support a captive colony on indigo snake populations. The results suggested that populations experiencing high road densities or high collection rates were likely to decline over time. These projects highlight some of the difficulties in conserving often-overlooked reptiles and amphibians in the southeastern United States and provide important tools for ongoing conservation projects working with these two imperiled species.

Globally, amphibian species have been in decline and a wide range of factors have been purported to be driving the decline. The Gulf Coastal Plain of Florida has a high degree of endemism and rarity and the biodiversity in the region includes a diverse suite of amphibian species. Degradation of habitat has been considered by many to be a major part of amphibian declines, however amphibian declines are complex and in many cases multiple factors are occurring in concert. My dissertation research examined aspects of habitat ecology and occupancy for two rare amphibians, Florida Bog Frog (Rana okaloosae) (Chapter 1, 2, and 3) and Reticulated Flatwoods Salamander (Ambystoma bishopi) (Chapter 5), that are both restricted to the Northern Gulf Coastal Plain. Further, for R. okaloosae I examined the influence of a sympatric congener, Bronze Frog (R. clamitans clamitans), on microhabitat selection (Chapter 1) and growth of tadpoles (Chapter 4). My overall goal was to be able to elucidate factors that limit the geographic range of R. okaloosae and A. bishopi and to identify habitat characteristics that managers could maintain or create to conserve or increase populations of these species. My first chapter examined the microhabitat relationships between R. okaloosae and R. c. clamitans. Rana okaloosae is endemic to northwestern Florida and is sympatric with R. c. clamitans, a more common and widely distributed congener. Further, the two species appeared to be syntopic, have overlapping breeding seasons, and are known to hybridize. The objectives of this chapter were to assess the microhabitat selection of both species and to assess differences in microhabitat use of males of both species during the breeding season. My modeling of habitat selection and comparison of variables used by each species suggests that males of these species select different resources when calling. Therefore, these sympatric ranids select for different resources at a fine scale, however there does appear to be some overlap among some selected habitat characteristics. In Chapter 2, I assessed the habitat use of R. okaloosae at multiple spatial scales. I surveyed for R. okaloosae and evaluated habitat characteristics at used sites and sites where I had no detections to develop among- and within-stream habitat models for R. okaloosae. Rana okaloosae used habitats with high amounts of emergent vegetation at both the among-stream scale and the within-stream scale. Emergent vegetation appears frequently in models of anuran habitat selection, particularly those that occur in fire-dominated landscapes. Further understanding the habitat requirements of R. okaloosae will allow land managers to use appropriate management activities (e.g., prescribed fire) that will increase emergent vegetation and potentially restore habitat that may help increase populations of R. okaloosae. In Chapter 3, I conducted aural surveys for R. okaloosae at two different spatial scales: range-wide and stream-level scales to understand how occupancy and colonization of R. okaloosae may be influenced by scale. My results suggest that at both spatial scales occupancy of R. okaloosae was best described by the presence of mixed forest wetlands at survey sites. At the range-wide scale, colonization and detection were constant across years, however, at the stream-level scale, colonization was predicted by the number of years since last fire and detection was best predicted by the additive combination of relative humidity and temperature. Occupancy of R. okaloosae was patchy at the range-wide and at the stream-level scales and colonization was low at both scales, while derived estimates of local extinction were moderately high. While R. okaloosae still occur in 3 watersheds where they were initially observed in the 1980's, one of the three watersheds appears to be very isolated and detections there are becoming very infrequent. In Chapter 4, I experimentally evaluated the effects of R. c. clamitans tadpoles on R. okaloosae tadpoles. My results suggest that there was limited influence of R. c. clamitans on R. okaloosae. Conversely, it appeared that Rana c. clamitans was more susceptible to intraspecific competition than interspecific competition. The lack of a strong competitive effect of Rana c. clamitans on Rana okaloosae suggests that competitive interactions among tadpoles may have a limited effect at the densities I examined. In Chapter 5, our objectives were to evaluate a suite of within-pool factors (i.e., vegetation structure, water level, and an index to presence of fish) that could influence occupancy of breeding wetlands by larval flatwoods salamanders on Eglin Air Force Base in Florida, USA. Site occupancy over a 4 year period was best described by a model that incorporated high herbaceous vegetation cover and open canopy cover. Detection probability was assessed, but it varied among years and was not included in the model. Our study suggests that managing the breeding habitat of flatwoods salamander for open canopies and dense herbaceous vegetation may contribute to this species' recovery. In conclusion, Chapters 1-3 of my dissertation contribute to a growing understanding about the habitat ecology of R. okaloosae. I have evaluated habitat use of R. okaloosae at multiple spatial scales. At the finest spatial scale R. okaloosae selected for sites that had an abundance of cover probably decreasing their risk of predation (Chapter 1). Similarly, in Chapter 2 at two spatial scales, among and within-streams, R. okaloosae selected for emergent vegetation. Finally, at the broadest spatial scale, range-wide, R. okaloosae were found to be associated with mixed forest wetlands (Chapter 3). I did not find strong support for competition between R. okaloosae and R. c. clamitans tadpoles, although there was some evidence of asymmetric competition (Chapter 4). Further, adult males of each species did not select the same habitat characteristics for calling sites, so there appeared to be some resource partitioning (Chapter 1). Finally, the presence of A. bishopi larvae was found to be associated with herbaceous vegetation and moderate amounts of canopy cover (Chapter 5). Results from Chapter 2 and 5 suggest that both R. okaloosae and A. bishopi are associated with habitat conditions that are likely a result of fire penetrating wetland areas. / Ph. D.

Terrestrial ecosystems in the southeastern United States have evolved with fire as a common disturbance and as a result many natural communities require the presence of fire to persist over time. Human development precludes natural fires from occurring within these communities; however, prescribed fire is considered to be a critical tool in the effort to restore fire-dependent ecosystems after decades of fire exclusion. Direct effects of fire on individual floral and faunal species as well as benefits to biodiversity at the landscape (gamma diversity) level have largely been supported in previous research. However, information on the effects of natural and prescribed fire on plant diversity at the local level (alpha diversity) is limited, particularly for southeastern forests. The applicability of the Intermediate Disturbance Hypothesis (IDH), which suggests that the highest levels of biodiversity are found at intermediate levels of disturbance, is also untested for North Florida upland plant communities. This study compared the effects of fire on local scale mean plant species diversity by examining burned and unburned portions of three fire-dependent communities to determine if there is an effect of prescribed fire on in alpha biodiversity. Alpha biodiversity was not significantly different (p=0.433) between burned and unburned fire-dependent plant communities in northern Florida, suggesting that prescribed fire does not affect plant species diversity in these communities and/or the IDH for plant communities is not supported at the time scale tested. However, the application of prescribed fire did result in changes in abundance of species, particularly with species such as Dicanthelium acuminatum, Quercus myrtifolia, and Vaccinium myrsinites, that respond positively to fire, which may have implications for associated faunal diversity.