2 resultados para PHYSIOLOGICAL ECOLOGY

em Bucknell University Digital Commons - Pensilvania - USA


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Fluctuations of food availability, habitat quality, and environmental conditions throughout the year have been implicated in the breeding success and survival of migratory birds. Levels of circulating corticosterone, the hormone involved in energy balance and the stress response in birds, are also affected by fluctuations in these variables, and also play a role in self-maintenance and survival. In addition to changes in behaviors and resource allocation, the metabolic effects of corticosterone increase the amount of free radicals in the body, which can cause oxidative stress and damage lipids and DNA. In this thesis, I assessed if diet and physiology during the breeding and non-breeding seasons contributed to the reproductive success, survival, and oxidative stress of a long-lived migratory seabird, Leach’s storm-petrel (Oceanodroma leucorhoa). I tested the hypotheses that 1.) diet and physiology throughout the breeding and non-breeding seasons predict reproductive effort; and 2.) corticosterone affects telomere length, a measure of oxidative damage. Through analyses of stable isotopes, corticosterone, and antioxidant capacity, I found that although there was variation in these measures of diet and physiology within the population, none of these factors during the breeding or non-breeding seasons correlated with reproductive effort or success. I also found that feather and plasma corticosterone did not predict telomere length. The life history strategies of Leach’s storm-petrels appear to be complex, and many factors likely contribute to self-maintenance and the decision to breed. Long-term monitoring of these variables may help identify relationships between trends in oceanographic variables during both the breeding and non-breeding seasons with reproductive effort and success, and survival.

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Telomeres are protective structures at the ends of eukaryotic chromosomes. The loss of telomeres through cell division and oxidative stress is related to cellular aging, organismal growth and disease. In this way, telomeres link molecular and cellular mechanisms with organismal processes, and may explain variation in a number of important life-history traits. Here, we discuss how telomere biology relates to the study of physiological ecology and life history evolution. We emphasize current knowledge on how telomeres may relate to growth, survival and lifespan in natural populations. We finish by examining interesting new connections between telomeres and the glucocorticoid stress response. Glucocorticoids are often employed as indices of physiological condition, and there is evidence that the glucocorticoid stress response is adaptive. We suggest that one way that glucocorticoids impact organismal survival is through elevated oxidative stress and telomere loss. Future work needs to establish and explore the link between the glucocorticoid stress response and telomere shortening in natural populations. If a link is found, it provides an explanatory mechanism by which environmental perturbation impacts life history trajectories.