Thesis (M.S.)--Oregon State University, 2011. / Printout. Includes bibliographical references. Also available on the World Wide Web.

Thesis (Ph.D.)--Drexel University, 2008. / Includes abstract and vita. Includes bibliographical references (leaves 77-88).

<div>Inferring genetic population structure in endangered, highly migratory species such as sea turtles is a necessary but difficult task in order to design conservation and management plans. Genetically discrete populations are not obvious in highly migratory species, yet require unique conservation planning due to unique spatial and behavioral life-history characteristics. Population structure may be inferred using slowly evolving mitochondrial DNA (mtDNA), but some populations may have diverged recently and are difficult to detect using mtDNA. In these cases, rapidly evolving nuclear microsatellites may better elucidate population structuring. Bayesian inference and ordination may be useful for assigning individuals to inferred populations when populations are unknown. It is important to carefully examine population inference results to detect hierarchical population structuring, and to use multiple, mathematically diverse methods when inferring and describing population structure from genetic data. Here I use Bayesian inference, ordination, and multiple genetic analyses to investigate population structure in Olive ridley sea turtles (ORs; Lepidochelys olivacea) nesting in northwestern Costa Rica (NWCR) and across the entire Eastern Tropical Pacific (ETP). Mitochondrial DNA did not show structure within NWCR, and existing data from prior studies are not appropriately published to compare NWCR to Mexican ORs. In NWCR, Bayesian inference suggested one population, but ordination suggested four moderately structured populations with high internal relatedness, and moderate to high levels of connectivity. In the ETP, Bayesian inference suggested a Mexican and Central American population, but hierarchical analysis revealed a third subpopulation within Mexico. Ordination revealed nine cryptic clusters across the ETP that primarily corresponded to Mexican and Central American populations but contained individuals from both populations, some from other, distant nesting sites. The subpopulation within Mexico was well-defined after ordination, and all clusters displayed high 10 internal relatedness and moderate genetic differentiation. Bottlenecks were detected in both putative populations, at seven Mexican and two Central American nesting beaches, and in six out of nine inferred clusters, including three out of four Mexican clusters. Bottleneck events may have played some role in cluster differentiation. Migration was significant from Mexico to Central America at multiple levels, but did not necessarily agree with potential migrants elucidated by ordination. Migration was generally lower between ordination-inferred clusters than between nesting sites or Bayesian-inferred clusters. Phylogenetic trees generally supported structuring by ordination, rather than by Bayesian inference. Structuring in ordination not tied to bottleneck events could be due to mating behaviors or patterns of nesting beach colonization dictated by environmental features. In this study, ordination provided a more practical and nuanced framework for defining MUs and DIPs in ETP ORs than did STRUCTURE. This may be due to hierarchical structuring within ETP ORs that may be present in other sea turtle populations and species. In the case of ETP ORs, hierarchical structure may be an artefact of recent population bottlenecks and subsequent recolonization of nesting beaches, or due to mating at foraging grounds or along migratory routes. Bayesian inference may not be the best method for population inference in highly migratory species such as sea turtles, which have a high potential for broad scale genetic connectivity, and therefore may display hierarchical population structuring not easily related to nesting sites. Future studies, and perhaps published studies, should incorporate Bayesian inference and ordination, as well as other measures of population divergence and descriptive statistics, when searching for population structure in highly migratory species such as sea turtles.</div>

La forte hétérogénéité de l'écosystème marin se traduit par une production inégale des ressources sur un large éventail d'échelles spatio-temporelles, qui conditionne par conséquent les déplacements des tortues marines. Considéré comme l’un des plus dynamiques au monde, le plateau des Guyanes est une région très complexe d'un point de vue océanographique et qui héberge trois des sept espèces de tortues marines présentes dans le monde (la tortue olivâtre, la tortue verte et la tortue luth). L'objectif de cette thèse était de comprendre comment les contraintes océanographiques peuvent-elles influencer les déplacements en mer de ces trois espèces. Le déploiement de 55 balises satellites sur des femelles reproductrices en Guyane française a permis de fournir des informations sur leurs trajectoires, sur leur comportement de plongée et sur les caractéristiques de leur environnement. Notre étude a mis en évidence une forte plasticité comportementale interspécifique qui semble être principalement dictée par les traits reproducteurs, les stratégies de reproduction, les conditions locales de l'habitat ou encore les adaptations physiologiques. / The strong heterogeneity of the marine ecosystem leads to a patchy distribution of the resources in time and space, shaping therefore the movements of sea turtles. Considered as the most dynamic ecosystem in the world, the Guiana shield is a highly dynamic system which hosts three of the seven sea turtle species in the world (the olive ridley, the green turtle and the leatherback turtle). The aim of this thesis was to understand how the oceanographic constraints can influence the at-sea movements of these three species during the reproduction and the migration phases. The deployment of 55 satellite tags on adult females in French Guiana provided information on their trajectories, their diving behavior and on the environment encountered. Our study shows a strong behavioral plasticity between species, which seems to be mainly dictated by the reproductive traits and strategies, the local conditions of the habitat and the physiological adaptations.

<p>Management of predation on sea turtle nesting beaches is vital to conservation efforts for the vulnerable loggerhead turtles (<i>Caretta caretta</i>) and olive ridley turtles (<i>Lepidochelys olivacea</i>). Sea turtles increasingly face threats from invasive and human-tolerant mammalian predators as human disturbances on nesting beaches rises. The intensity of mammalian predation has increased in Las Baulas National Park in Costa Rica which is an important nesting site for several species of threatened and endangered sea turtles. I analyzed loggerhead and olive ridley nest predation on four beaches in the United States and Costa Rica that were chosen for variations in degree of human disturbance and management strategies. My objectives were to 1) determine if egg predation rates differ at the four sites, 2) determine the most destructive predators at each location, and 3) suggest management options to alleviate mammalian threats to turtle clutches on Playa Grande and Playa Cabuyal in Costa Rica. My results show that the beaches without a nest protection or predator control program had very high rates of predation. Invasive mammalian predators and mammalian predators associated with human disturbance were the most destructive at the four sites. I recommend that regulations regarding dogs and the take of eggs from the beach are enforced at Playa Cabuyal and that physical nest protection is rapidly implemented at Playa Grande. I also recommend that the National Park consider managing raccoon predation by removing problem individuals, but caution that they do so in a way that maintains the animals’ role in the ecosystem.</p>