Browsing by Subject "life history"

Now showing 1 - 6 of 6
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    Choosiness as a component of life history strategies in cabbage white butterflies
    (2017-07) Jaumann, Sarah
    Many animals are choosy when selecting resources such as mates, food, or sites to lay eggs. For animals that lay eggs and do not subsequently care for their young, choosing the best sites for their eggs can greatly increase the survival and health of their offspring. Given these benefits, it is surprising that there is variation in choosiness; not all animals are choosy when laying eggs. Behaviors can be costly if they require energy and exhibit trade-offs with other traits that also require energy. I applied this idea to choosiness during oviposition, testing the hypothesis that animals are not choosy when being choosy is costly. In cabbage white butterflies, I demonstrated variation in choosiness and a trade-off between choosiness and fecundity, suggesting that being choosy is costly. If energetic costs determine degree of choosiness, then manipulating energy from food should lead to variation in choosiness. I manipulated food availability directly by varying nutrition and indirectly by varying butterfly density and thus potential competition for food. Density did not affect choosiness or other traits, but nutrition did. Poor adult nutrition led to lower levels of choosiness and lower fecundity but no changes in other traits. Thus, poor nutrition may decrease investment in multiple traits, including choosiness, rather than causing adaptive shifts in life history with increased investment in some traits. My results suggest that choosiness is energetically costly, but only direct cues about energy availability affect choosiness. These findings have implications for the health of butterflies and other pollinators.
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    Data Supporting 'Towards representing listed mussel species in risk assessment: A database and multivariate analysis of freshwater mussel life-history traits'
    (2021-01-04) Moore, Adrian; Galic, Nika; Brain, Richard; Hornbach, Daniel; Forbes, Valery; apmoore665@gmail.com; Moore, Adrian
    These files represent a literature review and database of freshwater mussel life-history data collected from published studies.
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    Developmental influences on stress-based responses to environmental change
    (2023-05) Shephard, Alexander
    A central goal in ecology, evolution, and behavior (EEB) is to understand how individuals and populations respond to environmental change. Many forms of environmental change are stressful, leading to functional impairments, fitness declines, and loss of genetic diversity from natural populations. In this dissertation, I consider factors that explain why organisms vary in their abilities to tolerate stressful environments. Taking a developmental approach, I address this question in the context of three research domains within the broader field of EEB: (1) the evolution of phenotypic plasticity, (2) life history evolution and senescence, and (3) population responses to anthropogenic change. In data chapter 1, I use a nematode (Caenorhabditis elegans) to test the hypothesis that genetic variation in generalized plastic responses to stress is associated with reproductive costs. Consistent with a cost of plasticity, I find that genotypes capable of a higher degree of stress response plasticity exhibit lower reproductive performance under non-stressful conditions. In data chapter 2, I use migratory North American monarch butterflies (Danaus plexippus) to test how metabolic stress influences life history variation. I find that increased flight activity early in adulthood promotes butterfly longevity and somatic tissue antioxidant production, supporting the idea that metabolic stress is a driver of life history plasticity. In data chapters 3 – 7, I use two butterfly species, D. plexippus and Pieris rapae (the cabbage white), to test a range of hypotheses related to developmental mechanisms associated with tolerance to novel anthropogenic stressors such as heavy metal and salt pollution. In chapters 3 – 4, I find support for the hypothesis that variation in heavy metal tolerance is related to organismal condition (i.e., the total amount of energetic resources individuals can acquire throughout development). In Chapters 5 – 6, I ask how anthropogenic increases in nutrient availability influence the emergence of life history variation. In chapter 7, I show that heavy metal tolerance can vary among insect pollinator species, and I highlight the need for more research on heavy metal tolerance in species of conservation concern. Overall, this work, shows that considering developmental mechanism can help predict stress-based responses to environmental change among a range of disciplines within EEB.
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    Harvesting native seed to supply landscape-scale restoration: evaluating risks and sustainable practices
    (2016-06) Meissen, Justin
    Seed supply limits large-scale restorations, which often rely on seed collection from remnant ecosystems. Overharvesting seed may deplete populations, exacerbate seed limitation, and jeopardize ecosystem integrity, but these risks have not been formally studied. Many life history traits are linked to species’ reliance on seed reproduction, and so may provide a useful framework to address seed harvest risks. I evaluated whether life history traits predict susceptibility to overharvest by comparing tallgrass prairies in Minnesota (USA) harvested at varying frequencies (every year, once per 3-5 years, unharvested). I identified species less likely to occur on frequently harvested sites then tested whether lifespan, clonality and seed production predicted harvest sensitivity. Short-lived, non-clonal species were sensitive to seed harvest while long-lived clonal species were not, suggesting that life history traits provide a means to predict seed harvest risk. To verify the predictive utility of life history traits and determine extinction risks from seed harvest over long restoration timeframes (25 years), I used matrix models of clonal Solidago canadensis and Anemone canadensis and non-clonal Rudbeckia hirta, Packera aureus, Zizia aurea, and Liatris ligulistylis to simulate seed harvest and extinction risk. I simulated 5 scenarios: no harvest; annual harvest at 50%/75% intensity; and triennial harvest at 50%/75% intensity. Non-clonal species were insensitive to triennial and 50% harvest, but susceptible to extinction risks of up to 92% with annual 75% harvest. Clonal species were insensitive to all harvest scenarios. To maintain populations of non-clonal species in the long-term, high intensity annual harvest should be avoided. To demonstrate the risk of overharvest in short-lived, non-clonal species and determine sustainable harvest regimes, I conducted a field experiment varying seed harvest intensity (0, 50%, or 100% seed removed) and management (burned or unburned) for R. hirta populations. I compared seedling recruitment and seed production among treatments, and found that seed production nearly doubled with burning. Moderate intensity harvest with burning allowed high levels of seedling recruitment, but high harvest intensity prevented recruitment, as predicted for a short-lived, non-clonal species. A regime combining moderate intensity harvest with fire management provides seeds while also conserving at-risk seed donor sources.
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    Life Stories and the Search for Educational Possibilities
    (2016-08) Carlson, Matthew
    The stories that people tell about their lives in the context of educational relationships draw attention to the possible experiences through which their lives could grow in meaning. In this collaborative reconstruction of one person’s life history, I present an interpretive retelling of several life stories that this person—Gurraacha Sabaa, an Oromo activist—told me as part of my work at the Dream Desk, a community-based education project designed to strengthen and support learning networks in the communities around a public library in Minneapolis. My interpretive retelling of Gurraacha’s life stories is based on the search for educational possibilities that organizes my work at the Dream Desk. This work requires a broad understanding of education. Thus, I define education as the process by which meaning grows in human lives. This broad definition of education is directly inspired by the work of philosopher John Dewey (1916). It is a way of translating a technical definition of education given by Dewey into the more practical terms required for my work at the Dream Desk. According to Dewey, education is a “reconstruction or reorganization of experience which adds to the meaning of experience, and which increases ability to direct the course of subsequent experience” (p. 82). In Dewey’s definition, the process by which meaning is added to experience is a process of growth. Further inspiration for this broad definition of education is drawn from the work of historian Lawrence Cremin (1976) and anthropologist Hervé Varenne (2007), both of whom recognize education as a fundamental human experience that is not limited to what takes place in schools. By attending to the life stories of one person, I explore the educational possibilities in his life as well as the particular conditions that restrict the realization of those possibilities. Our search for educational possibilities focuses on potential educational experiences related to Gurraacha’s interest in human rights advocacy. And our collaborative reconstruction of his life history focuses on the ways in which the meaning of human rights advocacy is growing in his life. While interpreting the trajectories of meaning revealed by his life stories, I also interpret the educational possibilities created by the ways in which his life history is collaboratively reconstructed in our educational relationship. These interpretations include attention to the practical guidance his life stories provide for our work together as well as the way in which they address me at a symbolic level, marking the differences between my experiences as a white American man and his experiences as an Oromo man. As Jackson (2002) describes, storytelling is both a strategy for “transforming private into public meanings” and a strategy for “sustaining a sense of agency in the face of disempowering circumstances” (p. 15). That is, life stories do much more than provide life with coherence and order (Linde, 1993; Ochs & Capps, 2001). Life stories have democratic and existential imperatives. These democratic and existential imperatives shape the intersubjective space created in the dialogue between my perspective and Gurraacha’s perspective, which is the basis for our educational relationship and our search for educational possibilities. In conclusion, I propose collaboratively reconstructed life histories as the foundation for an ethnography of educational possibilities, a form of social inquiry that not only supports educational action but also is shaped by its exigencies.
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    The rise and fall of the Ruffe (Gymnocephalus cernua) empire in Lake Superior
    (2017-12) Gutsch, Michelle
    Invasive species are a global problem, impacting property, habitats, ecosystem function, and native species. Our ability to predict future habitat and spread of aquatic invasive species is limited because it is challenging to collect and integrate information regarding life history, movement, and habitat, especially across continents. Ruffe (Gymnocephalus cernua), a demersal, invasive fish, has caused substantial ecological damage. Given the potential for ecological impacts, such as native fish declines, ongoing concern regarding the spread of Ruffe in the Laurentian Great Lakes is warranted. But there are significant research gaps regarding life history, movement, and Ruffe distribution in the native and non-native range. Therefore, the overall goals of my dissertation were to acquire life stage-specific data for Ruffe, including dispersal, seasonal, and spawning movements and characterize their life cycle and to develop a lake-scale species distribution model at 30-m resolution. Regarding the first goal, I found that Ruffe has characteristics that allow them to adapt to a range of environments, including rapid maturation, relatively long life and large size, batch spawning, genotypic and phenotypic plasticity, tolerance to a wide range of environmental conditions, broad diet, and multiple dispersal periods. To address the second goal, I developed a species distribution model for Lake Superior because Ruffe has established in the lake but is not yet widespread. I found that a variety of species distribution models constructed to predict Ruffe suitable habitat based on environmental data resolved to a variety of scales all performed similarly but varied substantially in the area of habitat predicted, particularly the offshore habitat area classified as suitable. I conclude that to interpret the outputs of the Ruffe species distribution models, both model performance and the ecology of Ruffe must be considered to better characterize its fundamental niche. Broadly, I demonstrate the importance of synthesizing the life stage-specific biology and distribution of an invasive species with species distribution models to advance our ability to predict the future habitat of an invasive species.