Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1991. / Vita. Abstract. Includes bibliographical references (leaves 41-45). Also available via the Internet.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 65-71). Also available via the Internet.

Northern bobwhite (Colinus virginianus) and swamp rabbits (Sylvilagus aquaticus) are species both strongly influenced by habitat loss and fragmentation in agricultural landscapes. Population declines for the bobwhite and the paucity of information regarding swamp rabbit prevalence add uncertainty to their potential for persistence in Illinois. Research has indicated that these 2 species rarely disperse long distances. In a metapopulation context, such limitations ultimately dictate species' ability to colonize habitat, thereby affecting their persistence. Since gene flow is one of the consequences of dispersal, I employed genetic investigations of the landscape features that affect gene flow, called landscape genetics, to aid the understanding of factors influencing the persistence of the northern bobwhite and swamp rabbit in an agricultural landscape. Tissue samples were collected from hunter harvested bobwhite in central and southern Illinois during 2007-2008. Tissue from trapped swamp rabbits and fecal pellets from swamp rabbit habitat were collected during 2004-2011 in the southernmost counties of Illinois. Microsatellite genetic markers were analyzed for each species. Bayesian clustering methods were used to find interbreeding groups. Levels of gene flow were assessed with F statistics. Correlations between individual genetic distances and landscape features provided an assessment of geographical attributes affecting gene flow. Northern bobwhite expressed less genetic structure among the southern and central counties of Illinois than expected from their sedentary reputation. Genetic differentiation among pre-defined subpopulations was low (FST <0.05) but significant. Genetic clusters were not tightly linked to geography. Individual-based analysis indicated that distance impacted gene flow more than the distribution of suitable habitat or highway barriers. Additionally, the distribution of suitable habitat on the landscape had a negative affect on gene flow indicating bobwhite may disperse through unsuitable habitat more readily than through suitable habitat. These results suggest that greater area of suitable habitat and improvement of existing habitat may be more beneficial to bobwhite than its arrangement or position on the landscape. Significant genetic structure was observed in swamp rabbits in the Cache River watershed of southernmost Illinois. Bayesian clustering indicated 4 distinct genetic groups inhabited the study area. Such structuring suggests swamp rabbits in the northernmost part of their range experience low connectivity among habitat patches and are consequently at risk for extinction in Illinois. Gene flow of swamp rabbits was tied to watercourses indicating their affinity for a water source impacts their dispersal tendencies. Gene flow was negatively impacted by highway barriers, which may interrupt swamp rabbit dispersal due to their avoidance of roads or land cover associated with roads. Alterations to swamp rabbit habitat that leads to loss, increased fragmentation, or increased road density may have severe negative impacts and should be avoided. Habitat improvement focused closer to watercourses may provide a greater benefit for swamp rabbits.

Understanding regulation of wild animal populations is important in ecological investigations and applied wildlife management. Progress in understanding regulatory processes has been hindered by a long-running debate over the role of density-dependent and density-independent variables in population regulation. Population regulation of exploited species is of particular interest because harvest theory is predicated on assumptions of density-dependent feedback. However, for many exploited species, the functional relationships and mechanisms of population regulation via density dependence are not quantified (e.g., Northern bobwhite (Colinus virginianus). Compounding this task is the lack of a mechanistic understanding of the influence of density-independent factors in population regulation. The overall goal of this dissertation is to investigate the roles of density-dependent and density-independent processes in bobwhite populations. Bobwhites are an excellent species to investigate the role and influence of density-dependent and density-independent factors due to their unique life history, wherein they can exhibit density dependence in survival, reproduction, or both. I provide support for the concomitant influence of density-dependent and density-independent processes operating to regulate bobwhite populations. My results support the importance of food and cover and the additive influence of density-dependent and density-independent factors on bobwhite annual survival. I also report evidence for the differential effects of covariates on survival phases. My results represent the first evidence of support for the Tub and Tap hypotheses on bobwhite survival. I also quantify a density-dependent effect on bobwhite recruitment. Collectively, these results provide new evidence for understanding the role of internal and external factors in bobwhite populations.

No description available.

no abstract provided by author / Master of Science

M.S.

M.S.

The fact that sensory modalities do not become functional at the same time raises the question of how sensory systems and their particular experiential histories might influence one another. Few studies have addressed how modified stimulation to earlier-emerging modalities might influence the functioning of relatively later-developing modalities. Previous findings have shown that enhanced prenatal tactile and vestibular (proximal) stimulation extended and delayed normal patterns of auditory and visual responsiveness to species-typical maternal cues in bobwhite quail respectively. Although these results were attributed to the increased amount of sensory stimulation, these results may be a function of when prenatal augmented proximal exposure took place. To address this issue the present study exposed groups of bobwhite quail embryos to equivalent amounts of augmented tactile and vestibular stimulation either at a time when a later-emerging modality (auditory or visual) was beginning to functionally emerge or when it had already functionally emerged. Results indicate that differences in the timing of augmented tactile and vestibular stimulation led to differences in subsequent auditory and visual responsiveness. Embryos were unable to learn a maternal call prior to hatching when enhanced proximal stimulation coincided with auditory functional emergence implicating a deficit in auditory functioning, but did learn a maternal call when enhanced proximal stimulation occurred after auditory functional emergence. Augmented proximal stimulation that coincided with visual functional emergence did not appear to influence normal visual responsiveness, but when proximal stimulation occurred after visual emergence, chicks displayed an accelerated approach response to species-typical visual cues. These findings support the view that the timing of enhanced stimulation to earlier-emerging modalities is important, and have meaningful implications for intersensory theory and research. / Ph. D.

Early perceptual learning capacity has been shown to correspond with the relative status of emergent sensory systems throughout prenatal and postnatal development. It has also been shown that young infants can learn perceptual information during perinatal development. However, the exact nature of the relationship between prenatal and postnatal perceptual development and the role of early experience on learning ability have yet to be examined. The present study examined how auditory learning capacity in bobwhite quail chicks is affected by the interrelationship between the developing auditory and visual systems in late prenatal/early postnatal development. Chicks were provided with auditory information during the period immediately prior to or the period following hatching. In addition, visual experience was either provided or attenuated during both the prenatal and postnatal periods. Findings revealed that chicks postnatally exposed to 10 min/hr of maternal auditory stimulation in lighted conditions required 72 hr exposure to the call in order to learn that bobwhite maternal call (Experiments 1A and 1B). Control chicks who experienced the prenatal egg-opening procedure demonstrated no naive preference for two individual variants of the bobwhite maternal assembly call (Experiment 2). However, embryos who received 10 min/hr of prenatal visual stimulation, or who were reared in prenatal darkness successfully learned a maternal call with only 24 hr of postnatal exposure (Experiments 3A and 3C). Embryos who received prenatal visual and postnatal darkened rearing conditions (a mismatch between prenatal and postnatal experience) showed deficits in postnatal auditory learning (Experiment 3B). Embryos who were exposed to 10 min/hr of prenatal maternal auditory stimulation and 10 min/hr of nonconcurrent visual stimulation remembered the maternal call into later ages of postnatal development than in previous studies when reared in lighted or darkened postnatal conditions (Experiments 4A and 4B). However, when all prenatal and postnatal visual experience were both removed from embryos' and chicks' environments, deficits in prenatal auditory learning and postnatal memory were observed (Experiment 4C). These results indicate that prenatal and postnatal learning in bobwhite quail occur differently, that mismatches in prenatal and postnatal experience interfere with postnatal auditory learning, and that prenatal learning and postnatal memory are affected by the amount of visual stimulation present within chicks' environmental milieu. In the broader scheme, these results provide further evidence that the auditory and visual systems are linked during early development and support an ecological perspective of learning and memory. / Ph. D.