Calcium, telomere length, and parasitism in passerines nesting at high elevation
Date
2020
Authors
Rodriguez, Marina D., author
Huyvaert, Kathryn P., advisor
Doherty, Paul F., Jr., advisor
Bailey, Susan M., committee member
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Abstract
Most organisms are exposed to numerous environmental stressors at various points throughout life, and, through natural selection, organisms' responses to such stressors have been optimized by natural selection for the best fitness outcomes. During the breeding season, wild vertebrates often make a trade-off between current reproduction and self-maintenance when dealing with environmental stressors. The total cost of reproduction is made up of all of the resources and energy that go into activities related to reproduction (e.g., nest building, finding a mate, foraging for food and nutrients related to offspring production, parental care) that do not go into self-maintenance. The cost of these activities can vary depending on resource availability, where limited resources can increase the cost associated with breeding due to increased energy associated with foraging and competing for the resource. In birds, calcium is a critical resource due to its importance in egg production and offspring development, and low calcium availability often leads to decreased reproductive success. In my first chapter, I used an experimental approach to assess the effects of supplemental calcium on reproductive parameters of Tree Swallows (Tachycineta bicolor) in a high elevation environment. Calcium-supplemented birds in my study area laid more, larger eggs, and had higher hatching success compared to control females. These results provide evidence that calcium availability is a constraint on breeding Tree Swallows at high elevation, perhaps due to the harsh conditions and concomitantly higher metabolic costs that force a costlier and more intense trade-off between foraging for food or for calcium. The increase in reproductive parameters for calcium supplemented nests in Chapter 1 highlights a cost associated with calcium foraging that constrains reproduction. For my second chapter, I aimed to better understand how calcium availability affects the cost of reproduction in mother Tree Swallows and offspring by using telomere shortening as a proxy of life stress and lifespan. Telomeres are terminal features of chromosomes consisting of repetitive DNA sequences that shorten with age and stress, and whose length is positively correlated with survival. I used telomere shortening as a proxy for the costs associated with reproduction to better understand life history trade-offs of Tree Swallows at high elevation sites. Similar to Chapter 1, I found that Tree Swallows supplemented with calcium had higher reproductive success, although I also found that supplemented nests had more telomere shortening compared to birds at control nests. These results provide evidence that Tree Swallows supplemented with calcium experience higher reproductive output at the cost of lower expected survival in the form of more telomere shortening. While investing resources in reproduction may lead to higher reproductive output for the current breeding season, this increase in reproductive success can come with a cost to survivorship. One way that resource allocation can shape survivorship is through investment in immune function. In many systems, however, more species-level and individual-level research is needed on host-parasite relationships before trade-offs between immune function and reproduction can be assessed. For my third chapter, I conducted a survey of avian Haemosporida: blood parasites that include those that cause avian malaria. I surveyed an avian community for haemosporidian parasites in the Colorado Rocky Mountains in order to estimate prevalence and diversity of blood parasites and to find species-level and individual-level characteristics that influence infection prevalence. I found that open cup nesters have higher blood parasite prevalence than cavity or open cup nesters. Additionally, male Ruby-crowned Kinglets, White-crowned Sparrows, and Wilson's Warblers had a higher prevalence of haemosporidian parasites compared to the other species analyzed, as did Red-breasted Nuthatches, which, like Ruby-crowned Kinglets, have a high body condition index. This chapter presents baseline knowledge of avian blood parasite presence, prevalence, and diversity across avian species in the Colorado Rocky Mountains and adds to our knowledge of host-parasite relationships of blood parasites and their avian hosts.
Description
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Subject
telomere
Haemoproteus
Haemosporidia
Plasmodium