Year of Award

2007

Document Type

Thesis

Degree Type

Master of Science (MS)

Degree Name

Organismal Biology and Ecology

Department or School/College

Division of Biological Sciences

Committee Chair

Lila Fishman

Commitee Members

Carol Brewer, Elizabeth Crone, Paul Spruell

Keywords

AFLPs, apomixis, clonal, genetic diversity, Hieracium aurantiacum, invasive

Abstract

Sexual reproduction is generally thought to provide long-term fitness advantages over asexual reproduction in the form of increased genetic diversity. Some work, however, suggests that asexual reproduction can also be advantageous. One situation when asexual reproduction provides an advantage is when colonizing a new range (Baker’s law), as in plant invasions. This study investigated the population structure of the invasive plant Hieracium aurantiacum. H. aurantiacum is an apomict – producing much of its seed asexually – and has become a common invasive in North America and New Zealand. The genetic diversity of H. aurantiacum was assessed over its invasive ranges in the Eastern and Western North America, as well as one location from its native range in the Czech Republic. Using AFLP analysis (with 45 loci), I generated genetic profiles of 225 H. aurantiacum and 60 individuals from 6 other Hieracium species (some native to and some introduced to North America) for comparison. Virtually no genetic variability was found in H. aurantiacum (clonal diversity was 0.035). Other Hieracium species, however, showed a range of diversity, showing clonal diversities from 0.154 to 1.0. One H. aurantiacum genotype dominated the sampled range (G1, in 51 of 53 sampled locations) and was identical to the sample from the Czech Republic. Two other genotypes were found in restricted ranges (G2 and G3). One was a population recently derived from nursery stock, and the other may represent another introduction or a mutated clonal line – each differed from each other and G1 at only two loci. It is quite possible that virtually all H. aurantiacum worldwide are clones. Despite this plant’s lack of genetic variation, it is able to grow over a wide invaded range, which may be due to phenotypic plasticity in fitness-related traits. Many theories about invasion success involve genetic diversity in invading populations to provide the necessary flexibility to flourish in a variety of habitats in an invaded range. In asexual invaders tending towards low genetic diversity, however, phenotypic plasticity of fitness-related traits is a more likely possibility.

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© Copyright 2007 Eli Stuart Loomis