Climate change and increasing anthropogenic activities are causing rapid changes to environmental and ecological processes in the Arctic Ocean. To better understand these changes, scientists have increased research efforts in these regions, but to date the number of studies on Arctic nearshore habitats are lacking. My dissertation responds to the paucity of information and investigates patterns in Arctic nearshore fish communities and food webs to gain insight to how these ecosystems may shift as these changes continue. I used multivariate statistical analysis to examine patterns in community structure and composition to determine that Arctic nearshore fish communities are largely driven by prey availability, salinity and temperature; and that species that are more abundant in warmer conditions are likely to increase in abundance as climatic conditions in the Arctic continue to warm. I improved the ability to apply stable isotope methods to Arctic food web studies by determining more appropriate model parameters using a laboratory-based isotope study on a common Arctic nearshore fish, and discuss its potential as a biological monitor species. These new parameters are used to confirm that a shift in prey resource dependence occurs across the seasonal shift from ice-covered winter to open-water summer conditions. Changes in basal resource dependence also occur later in the season across a latitudinal gradient where a shift to dependence on allochtonous inputs from nearby rivers increased trophic diversity. Using isotopic niche space theory, it was determined that the Arctic nearshore has a diverse prey base but that niche spaces of Arctic warm-water and cold-water species do overlap, and if numbers of warm-water fish continue to increase it will likely increase competition for resources for potentially less-adaptable, well-established, cold-water forage fish. On the other hand, if pelagic productivity is expected to increase and support larger fish biomasses, then there will be more than enough resources for warm-water and cold-water species to coexist, thus creating a more diverse prey base for piscivores in the Arctic.

Deciphering the factors underlying both long-term patterns of diversity and taxonomic turnover rates (i.e., extinction, and origination) has been one of Paleobiology's major foci for the past three decades. The importance of documenting these components is that they will expand our ability to interpret and model the evolutionary processes underlying those trends, highlight the evolutionary impact of historical events, and contribute to the formulation of robust predictions about the future of global diversity in response to the current anthropologically driven environmental changes. Accordingly, the first part of this study examines the possible occurrence of global marine evolutionary environmental controls into a `deep-time' perspective, using a statistical time-series approach between the most recent Phanerozoic global marine generic origination rates with coeval mean global marine geochemical and geological signatures of environmental proxies. After this examination, significant positive correlations were found between changes in origination rates and global mean signatures of 87Sr/86Sr and δ34S, as well as a significant negative correlation between variability in both origination rates and eustatic sea level. They suggest that over secular timescales, nutrient availability, as controlled by continental weathering, phosphorus recycling, and the relative extent of shelf exposure, is an important regulator of genus-level origination in the marine realm, with periods of increased nutrient availability associated with higher origination rates.

Behaviors can exhibit a wide degree of plasticity depending on the environmental context in which they are expressed. Despite this, repeatable differences have been found among and within individuals across a wide range of taxa. For my thesis, I investigated individual differences in foraging and parental care. In the first experiment, I assessed house sparrows (Passer domesticus) for domain-generality among neophobia, habituation and associative learning as they are all responses to novelty. While the results of the study find individual differences in each of these contexts the conclusion supported separate mechanisms for each response (domain-specificity). In the second experiment, I examined how the loudness of brood begging vocalizations influenced parent trip time, food load size brought to the nest and the amount of time spent in the box. The results of this study found individual differences in trip time and the time spent in the box with regard to the initial five seconds of begging loudness during a parent’s visit. Additionally, trip time was also influenced by the change in loudness within a visit. My findings reveal that individual variation may depend on the context in which individuals are measured.

Tall fescue is a widely used forage grass in the eastern USA and can form a symbiosis with a fungal endophyte, which can be beneficial for the plant but can cause livestock health issues. Little is known regarding the symbiotic response to predicted climate change. To address this knowledge gap, I analyzed tall fescue variety trial data collected throughout the U.S., exploring relationships between climate variables and yield for two different fescue cultivars that were either endophyte-free or infected. This study showed no endophyte or cultivar effect on fescue yield, but identified temperature, precipitation and location as significant predictors of yield, suggesting that local conditions were more important than endophyte presence or fescue genotype for this dataset. Using a field experiment located in central Kentucky, I quantified the ecophysiological responses of four tall fescue genotypes to endophyte presence, elevated temperature and increased growing season precipitation. In this study, tall fescue genotype was as important as endophyte presence in determining ecophysiological responses to climate change treatments. My thesis illustrates that tall fescue response to climate change will depend on host genetics, the presence and genetics of the fungal endophyte symbiont, and the specific changes to the environment experienced at a site.

Increasing human population size is increasing the demand for resources like timber, oil, tea, coffee, and other crops. Plantation crops mimic some aspects of native habitats, and there are studies that report the presence of some native anuran biodiversity in plantations. I focused on tea plantations in the Western Ghats-Sri Lanka Biodiversity Hotspot and studied the diversity and health of anurans in different habitats found within a tea cultivation area, near Munnar region in the Western Ghats, India. The landscape includes tea bushes, native evergreen shola forest patches, and eucalyptus forest stands. I reviewed 40 studies comparing amphibian species richness in plantations and primary forests. The age of the plantation, type of plantation, presence in a biodiversity hotspot, number of species in the dominant plantation type, number of species in the paired forest habitat, and latitudinal zone of the study, did not correlate with species richness, but plantations that had periodic harvesting had higher species richness than plantations that practiced clear-cut harvesting. I tested different methods of standard amphibian sampling in the field season 2012 in Munnar, and found that Visual Encounter Surveys (VES) in the shola habitat and Stream Transects (ST) were the most efficient. Using the VES and ST methods, I sampled amphibians in three upland habitats (tea, shola, and eucalyptus) at four different sites, and 150m of stream transects at each site, for two consecutive monsoon seasons. Fourteen species were encountered in both years and the community structure was similar across the years. The community structure at the four sites that was driven by the presence of exclusive species at each site and species composition in streams was similar across the landscape and was driven by the presence of similar species in streams across the four sites. Two hundred and sixteen anurans of 17 species, were tested for the presence of the lethal fungus Batrachochytrium dendrobatidis. The preliminary results from the Polymerase Chain Reactions were negative. My study provides baseline data for anuran diversity, composition, and health in the Munnar region of India and results of this project can be compared with tea plantations around the world.

The dispersal services of frugivores affect plant community assembly, persistence, and gene flow in the short-term, and in the long-term are critical to ensuring that tropical trees and palms can regenerate in disturbed areas and can migrate amidst climate change. Halmahera is the largest Moluccan island within the Wallacea biodiversity hotspot, yet data on its plant and animal distributions and interactions are almost null. I studied the tropical trees and palms of Halmahera and their seed dispersal dynamics. Chapter I explores the palms of the Moluccan islands through field-, herbarium-, and literature- based studies. The results of herbarium specimen collections are presented within a preliminary list of palms for Halmahera’s Aketajawe-Lolobata National Park, and contextualized in a review of regional palm biogeography. Expanding beyond the study of one plant family, Chapter II compiles and examines all the tree and palm taxa of the Moluccan islands in order to infer seed dispersal syndromes for each taxon, resulting in an analysis of over 900 taxa. Zoochory was found in 93% of plant families, and nearly 30% of endemic taxa rely primarily on dispersal by large-bodied frugivores. The role of a hypothesized keystone disperser (the Papuan hornbill, Rhyticeros plicatus ruficollis) is confirmed experimentally to disperse about 10% of Halmahera’s tropical tree and palm taxa. The final chapter encompasses an ex-situ germination trial and a year-long in-situ experimental study that examines the germination and recruitment of three palm species post-ingestion by Papuan hornbills, in four different habitat types representative of Halmahera’s landscape. Palms dispersed by hornbills into disturbed habitats and primary forests resulted in enhanced recruitment, although results varied by habitat and species. Hornbills aid both in forest conservation and recovery/assembly after disturbance. The results of this dissertation provide a foundation for further ecological studies and for enhanced conservation of Halmahera island.

The microbiome (microbial community) of individuals is crucial when characterizing and understanding processes that are required for organism function and survival. Microbial organisms, which make up an individual’s microbiome, can be linked to disease or function of the host organism. In humans, individuals differ substantially in their microbiome compositions in various areas of the body. The cause of much of the composition diversity is yet unexplained, however, it is speculated that habitat, diet, and early exposure to microbes could be altering the microbiomes of individuals (Human Microbiome Project Consortium, 2012b, 2012a). To date, only one study has reported on microbiome characterization in a shark (Doane et al., 2017; skin microbiome of the common thresher shark). A comparative characterization of microbiomes sampled from different shark species and anatomical locations will allow an understanding of the differences in microbiomes that may be explained by variance in shark habitat and diet. Florida leads as shark bite capitol of the world, with 778 unprovoked bites recorded since 1837, or 4-5 average bites per year. With only a few bites a year, there is not a lot of opportunities to study these bites. What can be studied, however, is how the microbial environment in shark’s teeth is composed. To understand overall microbiome composition, and if microbiomes are distinct from the environment, or specific by species or anatomical location (henceforth location), we characterized microbiomes from the teeth, gill, skin, and cloacal microbiomes of 8 shark species in south Florida (nurse, lemon, sandbar, Caribbean reef, Atlantic sharpnose, blacktip, bull, and tiger) using high throughput DNA sequencing of the 16S rRNA gene V4 region. There was a significant difference in microbial community richness among species, sample location, but not the interaction between species and location. Microbial diversity by location was significantly different for both the Shannon index and Inverse Simpson index. Samples examined by species had no significant difference in microbial community diversity overall for both Shannon and Inverse Simpson indexes. Microbial community diversity of samples by location and species combined significantly differed when submitted to an analysis of variance with the Shannon index, but not the Inverse Simpson index. Teeth microbial communities showed the most diversity based on both Shannon and Inverse Simpson indices. Teeth microbiomes are distinct but also share taxa with the water they inhabit, including potentially pathogenic genera such as Streptococcus (8.0% ± 9.0%) and Haemophilus (2.9% ± 3.3%) in the Caribbean reef shark. The lemon shark teeth hosted Vibrio (10.8% ± 26.0%) and the Corynebacterium genus (1.6%±5.1%). The Vibrio genus (2.8% ± 6.34%), Salmonella enterica (2.6% ± 6.4%), and the genus Kordia (3.1% ± 6.0%) are found in the nurse shark teeth microbial community. Strikingly, the Vibrio genus was represented in the sandbar shark (54.0% ± 46.0%) and tiger shark (5.8% ±12.3%) teeth microbiomes. One OTU related to traditionally non-pathogenic family Phyllobacteriaceae appear to be driving up to 32% of variance in teeth microbiome diversity. We conclude that south Florida sharks host distinct microbiomes from the surrounding environment and vary among species due to differences in microbial community richness. Future work should focus on bacteria found in shark teeth to determine if those present are pathogenic and could provide insights to bite treatment.

Extrafloral nectar (EFN) mediates food-for-protection mutualisms between plants and defensive insects. Senna mexicana var. chapmanii is a perennial legume native to the pine rockland habitats of south Florida. My dissertation focuses on how anthropogenic changes to the pine rocklands might affect EFN production by S. chapmanii, and the outcome of EFN mediated interactions. First, I investigated the influence of time of day, leaf damage, and leaf age on EFN production in S. chapmanii. Plants produced more nectar at night than during the day, and leaf damage resulted in increased EFN production. Furthermore, the response to leaf damage was greater when plants were damaged in the morning than when plants were damaged at night. Damage to young leaves elicited a stronger defensive response than damage to older leaves, in line with optimal defense theory. Second, I conducted a field experiment to determine the effects of ant activity, and light intensity, on herbivory rates, growth, and reproductive fitness in S. chapmanii. In shaded habitats, the presence of ants had no effect on herbivory rates, seed set, or plant size. In sunny habitats, however, plants with ants suffered less herbivore damage, produced more seeds, and grew larger over the duration of the one year study. Third, through a controlled greenhouse experiment I examined the effects of light intensity, and red/far-red light ratios, on EFN production in S. chapmanii. Plants in light-limited conditions produced less EFN, and leaf damage elicited increased EFN production regardless of light conditions. Ratios of red/far-red light, however, did not affect EFN production in either damaged or undamaged plants. Finally, I conducted a field study to determine how ants affect reproductive fitness in S. chapmanii. Over a period of eight months I observed the effects of ants on the activity of herbivores, predators, pollinators, and pre-dispersal seed predators. Relative pollinator efficiency, and rates of pre-dispersal seed predation, were unaffected by ants. Plants with ants, however, were quicker to establish, grew larger, and produced floral displays that attracted more pollinators. In S. chapmanii ants affected plant reproductive fitness simply by facilitating growth and establishment, with coincidental effects on reproductive investment.

Changes in global climate will likely increase climate variability. In turn, changes in climate variability have begun to alter the frequency, intensity, and timing of climate disturbances. Continued changes in the climate disturbance regime experienced by natural systems will undoubtedly affect ecological processes at every hierarchical scale. Thus, in order to predict the dynamics of ecological systems in the future, we must develop a more mechanistic understanding of how and in what ways climate disturbance affects natural systems. In South Florida, two climate disturbances recently affected the region, a severe cold spell in 2010, and a drought in 2011. Importantly, these disturbances affected an ecosystem of long-term, comprehensive, and persistent ecological study in the Shark River estuary in the Everglades National Park. The aims of my dissertation were to (1) assess the relative severity of these two climate disturbances, (2) identify effects of these disturbances on community structuring, (3) compare community change from the 2010 cold spell with community change from another extreme cold spell that affected sub-tropical China in 2008, (4) assess the effects of the drought on predator prey interactions in the Shark River and (5) apply a spatial approach to predicting population resistance to these events. My results show that the 2010 cold spell was the most severe cold event to affect the Shark River in the last 80 years, while the drought was the worst drought to occur in the last 10 years. The cold spell drove community change that was predictable based on the traits of component species, whereas community change was less predictable using trait-based approaches. When comparing community change from the extreme 2010 event in Florida with the event in China, I identified three consistencies related to community change from extreme cold events that occurred across both events that will help build generalized understanding of community resistance to increasingly extreme climate events in the future. From the trophic study, I found that the drought reduced prey for estuarine piscivores. Not only was prey biomass reduced, the drought drove a compositional shift in prey communities from fish to invertebrates, which are lower in calories. Last, I found that animal movement may create temporally dynamic resistance scenarios that should be accounted for when developing predictive models.

Fish distribution patterns and seasonal habitat use play a key role in the food web dynamics of aquatic ecosystems, including the Florida Everglades. In this study I examined the fine scale habitat shifts and movements of spotted sunfish, Lepomis punctatus across varying seasons and hydrologic conditions using in-situ field enclosures and Passive Integrated Transponder (PIT) systems. Data on fish use of three dominant Everglades marsh habitats and activity level were recorded continuously from January to August, 2015. Fish were more active and had the highest use of higher elevation habitats when water levels rose during an experimental reversal in mid-April. Fish activity was higher at increasing water levels relative to decreasing. Fish activity also varied with the rate of change, with the highest activity occurring during rapid increases in depth. Findings from this study provide insight on how fish response to changing water levels may affect foraging for wading birds, a key performance measure for Everglades restoration.