Date of Award

5-2009

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Plant and Environmental Science

Advisor

DeWalt, Saara J

Committee Member

Tonkyn , David

Committee Member

Bielenberg , Douglas

Committee Member

Bridges , William

Abstract

The potential for populations of invasive plants to differ in their response to stressful environmental conditions or in their invasiveness is an underexplored issue in determining introduced species' range limits. Introduced genotypes might differ in their response to freezing temperatures, soil type, or differing biotic factors within their introduced range. We examined the potential of Chinese tallow tree seeds (Triadica sebifera (L.) Small) collected from two genetically distinct areas of its introduced range in the United States (North Carolina and South Carolina) as well as from the northern and southern portions of its native range in China to germinate and for seedlings to survive winter conditions inland of the species' current coastal distribution in the state of South Carolina. Germination success of seeds from these four source populations was compared between fall plantings that mimic natural dispersal timing and spring plantings after the last frost in areas within (coastal sites) and inland (midland and piedmont areas) of its current distribution in South Carolina. In separate studies, overwinter survival, stem damage, budbreak timing and response to freeze events occurring before and after budbreak were compared among seedlings of the four source populations. Overall, seed germination success was lower in the colder piedmont areas than the warmer coastal sites, and seeds and seedlings from South Carolina genotypes showed greater reduction in germination success by inland winters, greater winter damage and reduced budbreak success in the field, and lower survival after prolonged freeze events than genotypes from North Carolina or China. These results show that genetically determined differences in environmental constraints exist among introduced genotypes of Chinese tallow, and that the North Carolina genotype shows greater potential for inland expansion than the South Carolina one. These population differences must be taken into account when evaluating the potential range expansion of Chinese tallow.

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