Date of Award:
5-1-2006
Document Type:
Thesis
Degree Name:
Master of Science (MS)
Department:
Biology
Department name when degree awarded
Life Sciences: Biology
Committee Chair(s)
Michael E. Pfrender
Committee
Michael E. Pfrender
Committee
Edmund D. Brodie Jr.
Committee
D. Richard Cutler
Abstract
The introduction of exotic species into a novel habitat, like all drastic environmental alterations, can lead to rapid evolution of both native and exotic species. Few studies have focused on the rapid adaptive evolution of native species to the introduction of a foreign species. Therefore, I wanted to determine if the introduction of exotic size-selective predators (salmonids) to alpine lakes in the Sierra Nevada, CA, has led to an adaptive response in the native prey species, Daphnia melanica. I conducted two common garden experiments with D. melanica from multiple populations, and collected data for morphological and life-history traits. With the data from one experiment, I compared phenotypic means of two types of populations--those that co-occur with fish and those in historically fishless lakes. Populations that come from lakes with fish were smaller, had fewer and smaller offspring, and were younger at each instar-specific age, differences that were consistent with predictions for adaptation in response to size-selective pressures caused by fish. For the second experiment, I estimated levels and distribution of within- and between-population quantitative genetic variation. The average estimate of within-population genetic variation for the population that co-existed with fish was fairly low, but not necessarily lower than for populations from two different fishless lakes. Populations from both lake types had high estimates for population divergence for body-size and offspring size traits. These results suggest that D. melanica have adapted to introduction of exotic predators. I also observed phenotypic means and within-population genetic variation for populations from lakes where fish were recently removed to determine how well these populations recovered. Populations from these lakes were phenotypically very different from each other, despite similar histories of fish introductions and removals. However, both populations had relatively high levels of population genetic variation for traits measured, indicating they had fully recovered since fish were removed. My data provide strong evidence for adaptation in several different populations to the introduction of an exotic predator and also indicate that these populations may quickly recover lost genetic variation if the non-native species is removed.
Recommended Citation
Fisk, Debra L., "Evolutionary Consequences of an Introduced Predator: Adaptive Change in Daphnia melanica in Response to Exotic Salmonids in the Sierra Nevada" (2006). Biology. 715.
https://digitalcommons.usu.edu/etd_biology/715
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