No description available.

<p>Dispersal has been long recognized as an important process in metacommunity dynamics, allowing isolated communities to interact with each other through the movement of individuals. Metacommunity theory and its four models (species-sorting, mass-effects, patch-dynamics and neutral) emphasize the significance of dispersal in the structure and composition of local community. Therefore, quantifying movements of individuals between patches is necessary to understand how systems will respond to varying degrees of connectivity and resulting species interactions. Many studies that have attempted to quantify dispersal, particularly of aquatic invertebrates, found conflicting results with respect to the intensity with which dispersal occurs. Moreover, investigations of invertebrate dispersal factors aquatic habitats have neglected to consider the influence of multiple factors such as life cycle stage, species, and external environmental features on dispersal rate via three vectors (wind, overflow, and animal transport). Colonization experiments have largely emphasized the importance of dispersal in influencing species richness, abundance and diversity but have yet to demonstrate direct comparisons between composition of dispersing species and local community structure. I investigated dispersal of aquatic invertebrates in a rock pool metacommunity, its possible influencing factors (species, life stage and the surrounding rock pool environment), and potential impact on species composition in local communities. To explore this, I used a combination of dispersal interception traps, colonization experiments and long tern biotic community surveys. I found dispersal occurs both rapidly and in high abundance across rock pools, particularly using wind and flow vectors, with minimal influence of connectivity, vegetation and ocean on dispersal rate. Although species and life cycle stages were highly variable and differed in their dispersal intensity, a high degree of similarity existed between composition of dispersing species and local community structure. Regional processes (i.e., dispersal), despite its unpredictability, is important for species assemblage and local community composition and necessary in the colonization of newly created habitats.</p> / Master of Science (MS)

Competition among individuals over shared resources reveals asymmetries in quality resulting in the formation of dominance hierarchies. These hierarchies act as a mechanism for social selection by partitioning resources among group-living animals. The following chapters describe my dissertation research which investigates the factors contributing to competitive asymmetries among broodmates as well as the short- and long-term consequences of the early social environment for the cooperatively breeding red-cockaded woodpecker (Picoides borealis). My research revealed that fledgling red-cockaded woodpeckers form male-biased, linear dominance hierarchies. Among fledgling males,, high relative nestling condition strongly predicted fledgling dominance, and this condition–rank relationship persisted through independence. Male nestlings are slightly larger and heavier than females; however, the sexual size dimorphism in mass is only present in mixed-sex broods, suggesting that the subtle structural size advantage gives males a competitive advantage over their sisters. Conflict rates among siblings increased with decreasing targeted feeding rates, and dominant fledglings were able to secure more food from provisioning adults through scramble competition. First-year survival favored males over females and dominant males over subordinates. Females were more dispersive overall than males, and subordinate males were more likely to disperse than dominants. The social environment prior to fledging influenced male dispersal decisions and subordinates delayed dispersal in the spring in situations where all dominants died over the winter. The probability of delayed dispersal in females was higher for females raised without brood-mates in one of two populations included in a long-term demographic data analysis. The availability of breeding vacancies may explain the differences in female dispersal behavior according to social environment between these populations. This research contributes to a greater understanding of the relative contribution of intrinsic benefits versus extrinsic constraints as an influence on delayed dispersal decisions in red-cockaded woodpeckers. Inter- and intra-sexual social rank is correlated with individual access to natal food resources and the probability of first-year survival. The intrabrood variation in dispersal strategies driven by social rank is sufficient to regularly produce both dispersal strategies among males and provides additional support that delaying natal dispersal is the preferred strategy for males in this system. / Ph. D.

Understanding the disease transmission dynamics in wildlife species can be difficult and can prove more complicated if the population structure of a socially living species is shaped by territoriality. Understanding the connections and movements of individuals between groups is vital to documenting how a disease may be spread. The presence of a heterogeneous landscape can further complicate attempts to describe transmission of an infectious disease. Here, I sought to understand how dispersal patterns of individual banded mongooses (Mungos mungo) could potentially influence disease transmission. Banded mongooses are small fossorial mammals that live in social groups ranging from 5 to 75 individuals and defend their territories against rival troops. The focal population of mongooses for this study lives across a complex environment in the Chobe district of northern Botswana and is faced with a novel strain of tuberculosis, Mycobacterium mungi. To infer genetic structure and individual movements between troops, I utilized microsatellite genetic markers and population genetic analyses. I found moderately strong genetic structuring (FST = 0.086) among 12 troops of banded mongooses in the study area in 2017-18. The best supported number of genetic clusters was K = 7, with a considerable amount of admixture between troops in urban areas. Compared to the average pairwise differentiation values of troops residing in natural habitats (FST = 0.102), urban troops had a lower level of differentiation (FST = 0.081), which suggests more gene flow between these troops. Among 168 mongooses genotyped, 20 were identified as being likely dispersers, with the majority moving across anthropogenic environments, suggesting that dispersal is heightened in urbanized areas. To assess whether temporal variation had an effect on genetic structure and gene flow between troops, I compared population genetic results from 5 troops in 2008 to those from the same 5 troops in 2017. Genetic differentiation was lower between troops living in urban environments than in natural environments for both 2008 and 2017. This result suggests higher gene flow across the anthropogenic landscapes at both times steps. The overall genetic structuring of the troops persisted over almost a decade, with the exception of observing more mixture and admixture in 2017 than in 2008. The effective population sizes (Ne) of troops were larger in 2008, which would indicate that genetic variability declined as time progressed. For 11 individuals confirmed to have M. mungi, an assignment test suggested that 3 mongooses were likely dispersers. This finding would contradict that of previous work, which suggested that sick banded mongooses refrained from dispersing. Sequencing of the M. mungi strains would be needed to determine whether these dispersers moved while sick or became infected after entering their new troop. These findings suggest that emphasis should be placed on closely monitoring banded mongoose troops in areas with heavy human influence. Here we see lower pairwise differentiation, higher gene flow estimates, and more frequent dispersal events. Heightened dispersal potentially can result in elevated disease transmission between troops in urban habitats. With disease transmission being the result of complex interactions between environment, host, pathogen, and time, results from this study contribute to understanding of disease transmission dynamics. / MS / Understanding how groups of the same species are connected is important for assessing how wildlife diseases spread across a landscape. For social species, connections are established by the movements of individuals between different groups; however, these can prove difficult to observe. Further complicating our ability to infer connections and movements, groups often live under different environmental conditions, which can influence movement rates. I studied banded mongooses (Mungos mungo) living in northern Botswana to assess the role of individual movement on the potential for disease transmission. Banded mongooses are small ground-dwelling mammals that live in troops of 5-75 individuals and defend group home-ranges. In Botswana, some troops are infected with a species of tuberculosis (TB, caused by the bacterium Mycobacterium mungi) that is unique to banded mongooses. Using molecular genetic tools, I estimated how genetically similar troops were to one other and estimated the rates of movement of individuals between troops. I found that troops living in urban environments tended to be more genetically similar to one other compared to troops living in natural environments within nearby Chobe National Park. I also detected more cases of individuals moving between troops in urban settings, with little evidence of movement between troops living in natural areas. These results suggest that there is more genetic exchange and a higher degree of connection between troops living in areas heavily influenced by people. With more connections between town-dwelling troops, we would expect to see higher rates of disease transmission between these urban troops, and hence should monitor their movement and health status closely. I also assessed how genetic structure and connections between banded mongoose troops changed over time by comparing results for collections of samples made in 2008 and 2017. Although more movement was detected in 2017, the overall pattern of genetic connections remained similar over the ten-year period. In particular, there was greater genetic similarity between troops in town compared to troops in natural environments in both years. Additionally, I genetically assigned TB-positive individual mongooses to their troop of origin to determine whether sick individuals moved out of their original troops. I identified three sick individuals as probable dispersers, although it is difficult with the information available to know whether they moved while infected or became ill after joining a new troop.

The studies presented here are an effort toward learning about the behavior of small mixed populations of German cockroaches. Of particular interest was the effect of female cockroaches on the behavior of the group, particularly the group formation within a harborage and the dispersal from a harborage. The effect of females was looked at with respect to female density and reproductive state. Populations aggregated at low female densities. This response increased when densities of gravid females increased but decreased when densities of non-gravid females increased. The effects of female reproductive state on dispersal could not be determined as non-gravid females developed egg cases by the end of the study. Increased female density caused increased dispersal of females and mid-instars. The mid-instars were the primary dispersers in each experiment. Early instars, excluding escapees, dispersed least. The results of these studies indicate the females of a population can mediate the behavior of that population and its members. It is postulated that this may be achieved by the production and/or regulation of sex, aggregation, and dispersal-inducing pheromones by females. / Master of Science

Reported survival rates, dates of family breakup, and dispersal patterns for yearling and subadult bears in hunted black bear (Ursus americanus) populations in North America are scarce. We estimated survival rates of yearling and subadult black bears from a hunted population in western Virginia during 1999 - 2002. We captured and marked 307 different individual yearling and subadult bears on 2 study sites, and attached ear tag transmitters or radio collars to 54 (34M : 20F) 1-year-old, 52 (23M : 29F) 2-year-old, and 35 (8M : 27F) 3-year-old black bears. We used the known fate model in program MARK to estimate annual, non-hunting, and hunting season survival for radio-marked bears of each age and sex class. Additionally, we used mark-recapture data in the recaptures only, dead recoveries, and Burnham's combined models within program MARK to estimate annual survival for each age and sex class. One-, 2-, and 3-year-old female survivorship was 0.87 (95% C.I. 0.78 - 0.92), while 1-year male survivorship was 0.32 (95% C.I. 0.20 - 0.47), and 2- and 3-year-old male survivorship was 0.59 (95% C.I. 0.47 - 0.71) from the Burnham's combined model. Survival rates for 1-year-old females (χ2 = 6.20, P = 0.01) and 2-year-old females (χ2 = 7.74, P = 0.01) were higher than males in each age category, respectively. However, we detected no difference between 3-year-old females and 3-year-old males (χ2 = 2.61, P=0.11), likely due to small sample size of males (n = 4). Low yearling and subadult survival is not likely a cause for alarm due to the importance of adult female survival to population growth and the promiscuous mating system in black bear populations. Family breakup is an important event in the life history of black bears, marking the initial dispersal and home range construction of yearling bears, and perhaps marking the timing of estrus and breeding opportunities for adult females. We monitored 6 black bear family groups with 12 yearlings (6M : 6F) to determine the timing of family breakup; we intensely monitored 3 of the family groups to document home range establishment and movements by 5 subadult bears (2M : 3F) following separation from their mothers. Estimated dates of family breakup were 28 May and 2 June. Family breakups occurred before peak dates of estrus on our 2 western Virginia study areas. We detected 2 reassociations between a mother and her yearling offspring. Following family breakup, female yearlings (n = 3) remained within or partially on their mothers' home range while subadult males (n = 2) left their mothers' home ranges. All yearlings (n = 5) shared ≥50% of post-breakup home range with their mothers. We studied the movements of 31 (11M : 20F) subadult black bears born on our 2 study areas in western Virginia and 70 (44M : 26F) subadult bears captured during the summer on the study areas for dispersal. No radio-marked, resident, subadult female bears exhibited dispersal behavior while 3 of 11 (27%) radio-marked, resident, subadult males dispersed (P = 0.04). Resident and summer capture male bears moved greater distances than females from yearling den location (χ2 = 8.54, P = 0.01, df = 2) or summer capture location (χ2 = 22.02, P < 0.01, df = 2); no female moved > 10 km between initial and final locations (x = 2.7 km, range 0.2 - 9.0 km). The greatest subadult male movement was 80 km (x = 13.4 km, range 0.6 -0.80 km), and dispersal movements primarily occurred within the 1 and 2-year-old age classes. Direction of movement between initial and final locations for dispersing bears was not random (Rayleigh's r = 0.56, P = 0.02); bears appeared to follow the orientation of the predominant ridgelines and avoided leaving the national forest. / Master of Science

Seed dispersal mutualisms, including seed dispersal by ants, are critical to the assembly of communities and the function of ecosystems. However, the consequences of human-caused global change factors, such as habitat fragmentation and climate change, for the future of these mutualisms are not fully understood. My dissertation consists of five chapters that investigated the effects of habitat fragmentation and climate change on ants and their seed dispersal mutualisms. Chapter 1 is an introduction that provides background information on habitat fragmentation and anthropogenic climate change and their impacts on biodiversity. In Chapter 1, I also introduce my study system of ant-mediated seed dispersal mutualisms, myrmecochory. My next two chapters (Chapters 2 and 3) explored the effects of reconnecting fragmented habitat patches with corridors in restored longleaf pine savanna systems in South Carolina. We used a landscape scale experiment to investigate how reducing isolation affects the assembly of ant communities over time (Chapter 2) and seed dispersal of the myrmecochorous forb, Piriqueta cistoides (Chapter 3). For Chapter 2, we found evidence that both habitat connectivity and edge effects underly the effects of corridors on ant communities over time. We found that connected patches accumulated ant species faster than isolated patches over time suggesting that corridors function by facilitating colonization. We also found evidence that edge effects play a role with greater ant functional group diversity in patches with higher edge than patches with lower edge amounts. For Chapter 3, we also found evidence of corridor and edge effects with ants dispersing seeds of P. cistoides longer distances in patches connected via corridors than isolated patches, but only in the center of patches. In Chapter 4, we investigated the effects of predicted climate change scenarios for seed dispersal mutualisms in eastern deciduous forests. For this chapter, we conducted a mesocosm experiment in which we crossed temperature with altered precipitation magnitude and frequency. Our mesocosms contained a common spring ephemeral wildflower, Sanguinaria canadensis, and whole colonies of their mutualist seed disperser, Aphaenogaster rudis. This design allowed us to collect high-resolution data on how ants interacted with seeds under different climate change scenarios that incorporated warming temperatures and altered precipitation. We found that warming effects depended on the precipitation treatment with negative effects of warming on the collection of seeds by ants under historical precipitation regimes and positive effects of warming under simulated precipitation conditions altered under predicted climate change. Finally, Chapter 5 describes my general conclusions from this body of work. Taken together, the research making up my dissertation provides valuable insights into how changing environmental conditions under habitat fragmentation and climate change may alter ant seed dispersal mutualisms. Importantly, we often found that the impacts of global change were context dependent and that our experiments were important tools in disentangling that context dependency. Further, this work demonstrates the value of understanding the basic ecology of the interactions among organisms. Understanding the natural history of organisms across changing environmental conditions will benefit the ways in which we conserve and restore ecosystems in a fragmented and warmer world. / Doctor of Philosophy / Most plants and animals engage in mutualisms, which are interactions between species in which both benefit from interacting with each other. The focus of this dissertation are the impacts of human-caused environmental change on the mutualism between ants and plants in which ants move a plant's seeds. The dispersal of ant-dispersed plants is considered a mutualism because the ants receive a food reward in the form of a fat- and protein-rich appendage that grows on the seed while the seeds of the plant get moved to a better location for germination. The mutualisms between ants and the plants they disperse are critical to how plants are distributed in many ecosystems, yet the consequences of human-caused environmental change, such as habitat loss and climate change, for these mutualisms are not fully understood. My dissertation consists of five chapters that investigated the effects of habitat fragmentation (the breaking apart of larger habitats into smaller, more isolated patches as a result of habitat loss) and climate change on ants and their seed dispersal mutualisms. My first chapter introduces background on the consequences of habitat fragmentation and climate change on organisms, ant seed dispersal mutualisms, and the potential effects of altered environmental conditions on seed dispersal by ants. My second two chapters (Chapters 2 and 3) explored the effects of reconnecting isolated habitat patches with habitat corridors (strips of habitat restored between the isolated habitat patches). In restored longleaf pine savanna systems in South Carolina, we used a long-term, landscape scale experiment to study how increasing connectivity and changing the shape of habitats via corridors affects ant community diversity over time (Chapter 2) and seed dispersal of the ant-dispersed plant, pitted stripeseed (Piriqueta cistoides) (Chapter 3). For Chapter 2, we found both habitat connectivity and patch shape effects underly the effects of corridors on ant community over time. We found that connected patches accumulated ant species faster than isolated patch types which suggests that corridors may function by facilitating colonization into the patches they connect. We also found evidence that patch shape plays a role in supporting greater ant functional group diversity in patches with greater perimeter (more edge habitat) than patches with less perimeter (less edge habitat). We found that ants in patches with more edge habitat represented a greater number of functional groups, which are categories that describe the roles ants play in ecosystems. For Chapter 3, we also found evidence of corridor and patch shape effects with ants dispersing seeds of pitted stripeseed longer distances in patches connected via corridors than isolated patches, but only in the center of patches. In Chapter 4, we investigated the effects of predicted climate change scenarios on seed dispersal mutualisms in eastern deciduous forests. For this chapter, we conducted an experiment in which we crossed temperature with altered precipitation in mesocosms, which are small, simulated ecosystems that allowed us to investigate the effects of warming and altered precipitation in a controlled setting. Our mesocosms contained a common spring ephemeral wildflower, bloodroot (Sanguinaria canadensis), and whole colonies of their mutualist seed disperser, winnow ants (Aphaenogaster rudis). We found that the effects of warming temperatures depended on the precipitation treatment. Warming had a negative effect on the number of seeds collected by ants under historical precipitation regimes, but a positive effect under simulated precipitation conditions under predicted climate change (higher in magnitude and lower in frequency). Finally, Chapter 5 describes my general conclusions from this body of work. Taken together, the research making up my dissertation provides valuable insights into how changing environmental conditions under habitat fragmentation and climate change may alter ant seed dispersal mutualisms. Importantly, we often found that the impacts of global change were context dependent. Our experiments were important tools in disentangling that context dependency. Further, this work demonstrates the value of understanding the basic ecology of the interactions among organisms. Understanding the natural history of organisms, especially their responses to changing environmental conditions, will ultimately benefit the ways in which we conserve and restore ecosystems in a fragmented and warmer world.

Movement behavior of Blattella germanica (L.) was investigated using two mark-recapture techniques 1) marking field collected populations of adult German cockroaches with a unique number, and 2) releasing strains of genetically marked German cockroaches to observe nymphal movement. Movement by adult cockroaches was studied by marking 3299 field collected German cockroaches in eight apartments. allowed for population. Adults were marked with Liquid Paper'. This recognition of specific individuals in the After marking, cockroaches were released at their original site of capture. Biological data was recorded on both nymphs and adults. Results indicate that movement of adult German cockroaches between apartments is minimal. Movement within apartments is greater, but not substantial. Movement appears to be linked to carrying capacity of the habitat (=apartment). When a vital resource -- food, water, or harborage -- becomes limited, adult movement can be detected when populations are large. Trapped populations in focus and non-focus apartments are spatially distributed in different ways. German cockroaches in non-focus apartments are trapped predominately in traditional sites of infestation kitchen and bathroom areas, with 90% of the collections occurring in these sites. In focus apartments trap collections indicate that one-third of the population is found in areas traditionally identified as non-preferred sites of infestation. Movement of German cockroach nymphs was investigated using releases of genetically marked strains of cockroaches. Collections of marked individuals were limited, suggesting that the strains used, especially eye color mutants, were not competitive in field environments. Results of this study were inconclusive. The feasibility of applying the aesthetic injury level concept to control programs within the urban environment rather than to pests occurring on the exterior was investigated. A random survey was conducted in non-elderly public housing projects in Roanoke, VA, Norfolk, VA, and Baltimore, MD. One hundred surveys were taken in each of the cities. The results of the survey indicate that the aesthetic injury level concept can not be successfully applied to control programs for insect pests occurring inside the home. are dependent upon the Tolerances extent of are variable, and the infestation experienced by each resident. It is speculated that as infestation levels decline, tolerance of the pest would also decline. / Ph. D.

Understanding the ecological processes that impact parasite abundance and distribution is critically important for epidemiology and predicting how infectious disease dynamics may respond to future disturbance. Digenean trematodes (Platyhelminthes: Trematoda) are parasitic flatworms with complex, multi-host life cycles that include snail first-intermediate hosts and vertebrate definitive hosts. Trematodes cause numerous diseases of humans (e.g. schistosomiasis) and livestock (e.g. fascioliasis), and impact the ecology of wildlife systems. Identifying the ecological mechanisms that regulate these complex, multi-host interactions will advance both our understanding of parasitism and the dynamics of infectious disease. By examining patterns of infection in Elimia (= Oxytrema = Goniobasis) proxima snails, my dissertation research investigated the environmental factors and ecological processes that structure trematode communities in streams. First, I examined temporal variation in trematode infection of snails in five headwater streams. Over a three year period, I found no consistent seasonal patterns of trematode infection. There was consistency across sites in trematode prevalence, as sites with high prevalence at the beginning of the study tended to remain sites of high infection, relative to lower prevalence sites. Second, I examined landscape level variation in trematode infection by characterizing the regional distribution, abundance and diversity of E. proxima infections in 20 headwater streams. I found a broad scale spatial pattern in trematode communities due to regional turnover in dominant species. This pattern was correlated with elevation, but there were no significant relationships with other environmental variables. Additionally, molecular characterization of trematodes indicated the presence of cryptic (morphologically indistinguishable) species complexes within this system, and variation in genetic diversity among trematode types may reflect differences in host dispersal abilities. Third, I examined trematode infection within a single stream network across multiple headwaters and the mainstem. I found a decreasing downstream gradient of trematode prevalence related to several environmental variables including elevation, snail density, conductivity, and stream depth. Additionally, headwater communities were nested subsets of the communities found in the mainstem. By combining approaches at different temporal and spatial scales, my dissertation research increases our understanding of the processes that impact the abundance and distribution of parasites. / Ph. D. / Understanding the ecology of wildlife parasite infection is critical both for public health and the conservation of global biodiversity. Digenean trematodes (Phylum: Platyhelminthes, Class: Trematoda) are parasitic flatworms that cause numerous diseases of humans (e.g. schistosomiasis) and livestock (e.g. fascioliasis), and can impact wildlife ecology. Trematodes have complex life cycles that involve multiple hosts. A typical trematode life cycle includes a series of three hosts: (1) a snail first-intermediate host; (2) an aquatic invertebrate or vertebrate second-intermediate host; and (3) a vertebrate final host. By identifying the ecological processes that are important in these complex, multi-host interactions, we can advance our understanding of parasites and infectious disease. Freshwater ecosystems serve as the transmission channels for many types of parasites, including trematodes, but we know relatively little about the ecology of parasites in streams. My dissertation research investigated the ecology of parasites in streams by examining patterns of trematode infection in stream snails, <i>Elimia</i> (= <i>Oxytrema</i> = <i>Goniobasis</i>) <i>proxima</i>. First, I examined seasonal changes in trematode infection of snails in five headwater streams. Over a three year period, I found no consistent seasonal patterns of trematode infection. There was consistency across sites in the level of trematode infection (i.e. sites with high levels of infection at the beginning of the study tended to remain sites of high infection, relative to sites with lower levels of infection). Second, I examined variation in trematode infection across a regional spatial scale by examining the number and types of trematodes infecting snails in 20 headwater streams in southwestern Virginia and northwestern North Carolina. Across the region, I found a broad spatial pattern in the geographic distribution of trematodes due to changes in the dominant type of trematode infection. This pattern was related to elevation, but not to any other environmental variables we measured. Additionally, I obtained genetic sequences from these trematode samples, and this revealed the existence of additional trematode species that we could not distinguish based on visual examination of morphological features. Furthermore, differences in the genetic diversity of trematode species may be related to differences in the mobility of trematode host species. Third, I examined trematode infection at eight locations within a single stream. I found that trematode infection decreased from upstream to downstream, and that this pattern was related to several environmental variables including elevation, snail density, conductivity, and stream depth. By combining examinations of infection patterns over time and at different spatial scales, my dissertation research increases our understanding of the processes that impact parasite transmission in freshwater ecosystems.

Master of Arts / Department of Geography / J. M. Shawn Hutchinson / Prairie dogs (Cynomys spp.) are social, ground-dwelling rodents native to North American short- and mixed-grass prairie. They are also the main prey of the Federally-endangered black-footed ferret (Mustela nigripes). At the same time, prairie dog colonization is highly opposed by most agricultural landowners. Therefore nonlethal population management techniques must be investigated. This paper presents the results of research on the effectiveness of ungrazed vegetative barriers composed of native plants at limiting prairie dog dispersal away from a ferret reintroduction site in northwest Kansas. Data was collected on barrier quality and condition as well as estimates of population densities of immigrant prairie dogs, dispersing through the vegetative barrier to reoccupy previously extirpated colonies on properties surrounding the ferret reintroduction site. Using strip transects and aboveground visual counts to estimate population densities and visual obstruction ranking techniques to sample barrier condition, statistical analysis of the data indicated that while barrier condition increased over time, it was not effective at limiting prairie dog emigration from the black-footed ferret reintroduction site.