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Crowder, Michelle Elizabeth

Plant Biology

2006

MS

To test the prediction that peripheral populations are genetically compromised relative to central populations, seeds were collected from three peripheral populations and ten central populations in Vermont, New York, and the Great Lakes region. Common garden studies were used to estimate broad sense heritabilities for quantitative traits, which were in turn used to relate genetic variation within a population to population size. Performance related to fitness was also compared to population size. Crosspollinations were performed at various scales to observe the effects of inbreeding and outbreeding on F1 and F2 fitness. Contrary to theoretical predictions, I found that large populations are neither significantly more variable nor more fit than small populations. In addition, some populations are generally more variable than others, regardless of population size. Cumulative cross fitness did not vary according to cross type or among peripheral and central populations, suggesting that neither population type shows a preference for inbreeding or outbreeding. Recombination in F1 hybrids between Vermont mothers and New York fathers significantly decreased cross fitness, suggesting outbreeding depression, but because we do not have data on the parental generation, other phenomena such as F1 heterosis cannot be ruled out.