Molecular Genetic Diversity and Population Genetic Structure of the Commercially Important Tropical Forest Tree Species Eucalyptus urophylla

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Title: Molecular Genetic Diversity and Population Genetic Structure of the Commercially Important Tropical Forest Tree Species Eucalyptus urophylla
Author: Payn, Kitt
Advisors: Alexander Myburg, Committee Member
William Dvorak, Committee Chair
Gary Hodge, Committee Member
Ron sederoff, Committee Member
Abstract: Eucalyptus urophylla is an important plantation species in countries with tropical and subtropical climates. Its natural distribution is limited to seven islands in eastern Indonesia. Larger populations are found on the islands of Timor and Wetar, whereas smaller populations occur on the islands of Alor, Pantar, Lomblen, Adonara and Flores. Of concern is the depletion in the species' genetic resource as a consequence of land conversion to agriculture. Proficient management of the genetic resource, with respect to both conservation and breeding programs, requires an understanding of the level of genetic diversity and population structure across the species' native range. This may be achieved through the application of DNA marker techniques. Chloroplast DNA sequence variation in E. urophylla was studied to gain insight into its historical seed migration routes among the islands. Twenty haplotypes were identified. A high level of chloroplast genetic differentiation (GST = 0.581) was observed. Chloroplast haplotype diversity exhibited a decreasing trend from east to west in the species' range, consistent with an east-to-west colonization route. Twelve nuclear microsatellite markers were used to infer the geographical distribution of nuclear genetic diversity. High levels of microsatellite diversity were observed throughout 19 geographically defined populations (HE = 0.703 to 0.776). Genetic differentiation among populations was low (FST = 0.031). A Bayesian clustering approach revealed a cryptic population structure comprising two genetically homogeneous groups, broadly structured according to geography. In order to gain insight into the diversity and population structure of genes associated with economically important traits, we investigated the geographical distribution of single nucleotide polymorphism (SNP) haplotypes in two wood formation genes (sucrose synthase1, and cinnamyl alcohol dehydrogenase2). High levels of SNP haplotype diversity were observed throughout the natural populations (Hd = 0.58 to 0.76). Low levels of population genetic structure were observed for the SNP haplotypes of each gene (FST < 0.08). The results of this study provide improved direction for conservation and breeding strategies in E. urophylla.
Date: 2008-07-23
Degree: PhD
Discipline: Forestry

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