The hollow curve species abundance distribution describes the pattern of large numbers of rare species and a small number of common species in a community. The species abundance distribution is one of the most ubiquitous patterns in nature and many models have been proposed to explain the mechanisms that generate this pattern. While there have been numerous comparisons of species abundance distribution models, most of these comparisons only use a small subset of available models, focus on a single ecosystem or taxonomic group, and fail to use the most appropriate statistical methods. This makes it difficult to draw general conclusions about which, if any, models provide the best empirical fit to species abundance distributions. I compiled data from the literature to significantly expand the available data for underrepresented taxonomic groups, and combined this with other macroecological datasets to perform comprehensive model comparisons for the species abundance distribution. A multiple model comparison showed that most available models for the species abundance distribution fit the data equivalently well across a diverse array of ecosystems and taxonomic groups. In addition, a targeted comparison of the species abundance distribution predicted by a major ecological theory, the unified neutral theory of biodiversity (neutral theory), against a non-neutral model of species abundance, demonstrates that it is difficult to distinguish between these two classes of theory based on patterns in the species abundance distribution. In concert, these studies call into question the potential for using the species abundance distribution to infer the processes operating in ecological systems.

A total of 733 bird nests, representing 55 species from 23 habitats, was examined. Forty-nine percent of the nests of 39 bird species were infested with 16 species of Protocalliphora. Infestation of bird nests by Protocalliphora is believed to be related to a number of factors, which are discussed. Loosely constructed nests, nests heavily saturated with feces, and nests occupied early in the season had low rates of infestation. Nests of colonial birds were more frequently infested than those of solitary birds. Nests of some birds were rarely or never infested. Sixteen species of Protocalliphora are differentiated and their host and habitat preferences discussed. Some species appeared to be either host or habitat specific, but infestation by many species appeared to be controlled by a combination of host and habitat specificity. Aspects of the life history of the species of Protocalliphora are discussed. An aggregation of adult Protocalliphora at a Bank Swallow colony was noted. Mortality in nestling birds from the feeding of Protocalliphora was rarely observed, except in nests of Yellow-headed Blackbirds and Cliff Swallows, where other factors may have contributed to high mortality.

A major goal in restoration is to reestablish native plant communities. There are several ways to reestablish species, but for large areas the most logistically feasible approach is to sow seed of desirable species. However, most wetland seeds are buoyant and are extremely difficult to establish in designated areas before floating away. In upland areas, tackifiers have been used to stabilize hill slopes from erosion and to keep seeds in place. The tackifier works as an adhesive that binds the seeds to the soil. However, the use of a tackifier has not been widely employed in wetland restorations, and prior to its broad implementation into wetland restoration practice, it is important to determine if tackifiers will hold up in wetland conditions. In greenhouse studies, we tested the effectiveness of different tackifier types and concentrations on Bolboschoenus maritimus seedling emergence, the influence of soil moisture and flooding on the duration of tackifier effectiveness, the effect of a mulch addition on tackifier effectiveness (Bolboschoenus maritimus, Schoenoplectus acutus and S. americanus), the effectiveness of pre-germination in enhancing Bolboschoenus maritimus seedling emergence using a tackifier, and the effectiveness of tackifier over time. We concluded that the use of a tackifier was effective at keeping seeds from washing away for at least 15 days, a mulch addition did not enhance tackifier effectiveness, and pre-germination did not benefit B. maritimus seedling emergence. The results from this study provide strong evidence that the use of a tackifier could be an effective solution to establish bulrush species in designated areas in wetland restorations.

Invasive species are organisms whose introduction and spread in exotic ranges result in a multitude of ecological impacts. Understanding the factors that constrain the exotic distributions of invasive species is of considerable interest. Biotic associations formed with taxa in the invaded community may be particularly important in shaping invader distributions. These associations emerge from interactions between the traits of the invasive species and some subset of the traits present in the invaded community. Focusing on how organism traits influence the outcomes of biotic interactions may inform predictions of invader distributions. This kind of trait-based approach may be most easily applied to systems where invaders specialize on particular hosts because such associations imply a close correspondence between the traits of the invader and hosts. This dissertation focuses on the South American cactus moth (Cactoblastis cactorum, Lepidoptera: Pyralidae), an invasive consumer in North America whose larvae infest prickly-pear cacti (Opuntia spp.). Chapter One is a brief introduction providing background and context to the presented research. In Chapter Two, I quantify Opuntia morphological and tissue macronutrient traits hypothesized to correlate with patterns of C. cactorum host use. Tissue macronutrient traits appear important in predicting C. cactorum infestation whereas a model containing Opuntia morphological traits had poor predictive ability. Chapter Three describes a method that uses host Opuntia identity and availability to estimate habitat suitability in order to predict the North American distribution of C. cactorum. I then simulate C. cactorum dispersal relative to scenarios of habitat suitability and Opuntia availability. Chapter Four alters the model in Chapter Three so that habitat suitability for C. cactorum is determined by the availability of trait-based groupings of Opuntia hosts. I then simulate C. cactorum dispersal via a different method from that described in Chapter Three. In Chapters Three and Four, I evaluate the degree of similarity among model predictions and the relative contribution of modeling constraints in generating variation in this similarity. Chapters Three and Four predictions were most affected by estimates of abiotic suitability and dispersal constraints, respectively. Chapter Five is a short summary of my results and a discussion of their more general applicability.

I evaluated effects of 5 pine plantation establishment regimes 6 – 8 years postestablishment on loblolly pine (Pinus taeda) growth, vegetation characteristics, nutritional carrying capacity for white-tailed deer, and breeding birds in the Lower Coastal Plain of Mississippi. Treatments combined mechanical site preparation (MSP), chemical site preparation (CSP), and herbaceous weed control (HWC) designed to represent a range of operational intensities. Chemical SP provided greater long-term control of woody competition than MSP, but did not provide significant pine growth advantage. Vegetation richness, diversity, and structure were best maintained with MSP and year 1 banded HWC. Canopy cover appears to be shading out herbaceous understory and altering composition of woody understory toward more shade-tolerant species. Total forage biomass and 3 levels of carrying capacity declined on average 54% each year. Avian metrics decreased as treatment intensity increased. Regionally important species were influenced positively by greater vegetation coverage attained by banded HWC.

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Approximately 90% of flowering plants depend on pollinators for reproduction. The stability and effectiveness of plant-pollinator interactions are crucial for ecosystem function. Increasing numbers of non-native plants are naturalized in plant communities and may alter pollination success of native plant species. Thus, invasive species have the potential to alter community function and stability. However, the effects of invasive species on community-wide plant-pollinator interactions are poorly understood. While the effects of invasive species on the structure of plant-pollinator networks are well studied. However, these studies have relied on pollinator visitation data that is only one component of the pollination process. Thus, the effects of invasive species on pollen transport and pollen transfer dynamics remain unknown and this may misrepresent the true nature of invasive effects on community-wide plant-pollinator interactions. Pollen transport networks may give more accurate representations of plant-pollinator interactions by providing information on pollen collection by floral visitors. Therefore, in this study I evaluate the effect of the invasive Cirsium arvense on pollen transport networks to improve our understanding of the impact that invasive plants have on community-wide plant-pollinator interactions. Pollinators were collected on one invaded and one non-invaded site once weekly throughout the flowering season (May- August of 2017). Pollen was isolated for each insect and pollen samples were identified with a pollen reference library and counted using a hemocytometer. 154 insect morphospecies were collected carrying 73 pollen species. Preliminary results indicate that Cirsium arvense has no impact on network structure: connectance (0.15 and 0.18), link density (3.01 and 2.23), and weighted nestedness (0.68 and 0.75), for invaded and non-invaded respectively. However, the role of individual species within the network seems to vary between sites suggesting that Cirsium arvense may change community dynamics (identity of species-pair interactions). Future analysis will evaluate invasive species effects at the species level.

Dravet syndrome (DS) is a severe, pediatric-onset epilepsy disorder linked to loss-of-function mutations in the sodium channel gene SCN1B. DS patients have a high risk of Sudden Unexpected Death in Epilepsy (SUDEP). Cardiac arrhythmias have been implicated as a potential cause underlying SUDEP. An exact pathway for how mutations in SCN1B leads to arrhythmia in DS is unclear. One cellular component linked to regulation of cardiac homeostasis are mitochondria, known as “the powerhouse of the cell” due to their ability to produce cellular energy (ATP) via the electron transport chain (ETC). The ETC is a major producer of reactive oxygen species (ROS). Typically, ROS are buffered by cellular antioxidants, to prevent oxidative stress, an imbalance of ROS that can lead to cell damage. Our previous work indicates that cardiac arrhythmias may result from mitochondrial instability and imbalances between ROS production and buffering. We analyzed whether Scn1b-/-mice are susceptible to arrhythmias due to altered mitochondrial ATP generation, ROS production, and compromised cellular antioxidant defenses. We isolated cardiac mitochondria from postnatal day (P) 15-20 KO and Scn1b+/+ (WT) mice. To assess mitochondrial ATP and ROS production, high-resolution respirometry (O2k, Oroboros) was used to measure mitochondrial O2 and H2O2 flux. We used a substrate-uncoupler inhibitor (SUIT) protocol to elucidate flux under different ETC pathways, including Complex I- and II-linked respiration. As a next step, we evaluated expression of superoxide dismutase (Sod) proteins associated with mitochondrial antioxidant defenses, including Cu/Zn-Sod (Sod1) and Mn-Sod (Sod2) in hearts from KO and WT mice pre- (P10) and post- (P17) seizure development. After addition of substrates supporting Complex-II linked respiration (succinate, ADP) there were no differences in O2 flux between mitochondria isolated from KO and WT hearts. Upon further addition of pyruvate to mitochondria to stimulate Complex I, O2 flux was significantly reduced (p < 0.0001) in mitochondria from KO mice, when compared to WT. Moreover, upon titration of rotenone (a Complex I inhibitor) its negative effect on O2 flux was not as substantial in KO mitochondria as in WT, suggesting that mitochondria from KO have deficits in Complex-I linked respiration. Furthermore, we detected significant differences in ROS production by mitochondria isolated from KO animals. Under conditions of reverse electron flow (succinate as substrate), a state where ROS production is highest, H2O2 flux was elevated significantly (p = 0.048) in mitochondria isolated from KO mice, compared to those isolated from WT. During our analysis of Sod expression, we found that Sod1 (p = 0.01) and Sod2 (p = 0.01) expression is significantly decreased at P17 in KO hearts compared to WT. Overall, our results suggest imbalances between mitochondrial activity and antioxidant defenses, which may underlie increased arrhythmia susceptibility in KO mice.

Invasions of exotic species are one of the primary causes of biodiversity loss on our planet (National Research Council 1995). In the marine environment, all habitat types including estuaries, coral reefs, mud flats, and rocky intertidal shorelines have been impacted (e.g. Bertness et al. 2001). Recently, the topic of invasive species has caught the public's attention. In particular, there is worldwide concern about the aquarium strain of the green alga Caulerpa taxifolia (Vahl) C. Agardh that was introduced to the Mediterranean Sea in 1984 from the Monaco Oceanographic Museum. Since that time, it has flourished in thousands of hectares of near-shore waters. More recently, C. taxifolia has invaded southern Californian and Australian waters. Since the waters of Florida are similar to the waters of the Mediterranean Sea and other invasive sites my study will focus on determining potential invasion locations in Florida. I will look at the present distribution of C. taxifolia - native strain in Florida as well as the distribution of the whole genus around the state. During this study, I address three questions: 1) What is the current distribution of Caulerpa spp. in Florida? 2) Can I predict the location of potential Caulerpa spp. invasions using a set of environmental parameters and correlate them to the occurrence of the algae with the support of Geographic Information System (GIS) maps? 3) Using the results of part two, is there an ecological preferred environment for one or all Caulerpa spp. in Florida? To answer these questions, I surveyed 24 areas in each of 6 zones chosen in a stratified manner along the Floridian coastline to evaluate the association of potential indicators Caulerpa. Latitude, presence or absence of seagrass beds, human population density, and proximity to marinas were chosen as the 4 parameters expected to correlate to Caulerpa occurrences. A logistic regression model assessing the association of Caulerpa occurrence with measured variables has been developed to predict current and future probabilities of Caulerpa spp. presence throughout the state. Fourteen different species of Caulerpa spp. were found in 26 of the 132 sites visited. There was a positive correlation between Caulerpa spp. and seagrass beds presence and proximity to marinas. There was a negative correlation with latitude and human population density. C. taxifolia – aquarium strain wasn't found. Percent correct for our model was of 61.5% for presence and 98.1% for absence. This prediction model will allow us to focus on particular areas for future surveys.

Mangrove ecosystems are critical to Florida, providing economic resources to humans, and untold ecological resources to estuarine organisms. In Florida's estuaries, mangrove ecosystems have suffered significant losses due to natural and human disturbances; these disturbances potentially leave mangrove communities vulnerable to invasion by the opportunistic exotic, Schinus terebinthifolius (Brazilian pepper). Prior experiments have suggested that Schinus terebinthifolius is unable to survive under marine conditions and poses no long term threat to mangrove systems. However, this contradicts field observations where Schinus terebinthifolius was found growing in the intertidal zone of Mosquito Lagoon alongside three native species of mangroves, Rhizophora mangle, Avicennia germinans and Laguncularia racemosa. The purpose of my study was to evaluate competition between the invasive S. terebinthifolius and these three native species of mangroves in the coastal estuarine system along the east coast of Central Florida in Canaveral National Seashore. The effects of competition were evaluated by testing the ability of S. terebinthifolius to: 1) chemically inhibit growth of mangrove propagules, 2) invade new coastal habitats by dispersing seeds in the water, 3) alter species richness and abundance of the flora when present in a mangrove system, and 4) recruit and survive in mangrove habitat. By better understanding the invasibility and impact of Schinus terebinthifolius on mangroves, coastal resource managers will be able to develop the most effective management strategies to prevent this exotic from altering the structure and productivity of the mangrove ecosystem.