Molecular genetics and the conservation of plants: two case studies

Oliver, Christina T. (2004) Molecular genetics and the conservation of plants: two case studies. PhD thesis, University of Glasgow.

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The Convention on Biodiversity (CBD) signed at the 1992 Earth summit in Rio formally
recognized biodiversity at the habitat, species, and genetic levels. For species and habitat
biodiversity there is a well-established set of frameworks under which conservation
programmes are constructed and delivered. From a genetic biodiversity perspective,
however, there is no clear consensus on how best it should be measured, or how
conservation programmes should be implemented.
The major reasons for conserving intra-specific genetic biodiversity can be summed up
under two inter-related themes, (1) Protecting a broad spectrum of genetic biodiversity,
and (2) Maintaining evolutionary fitness and adaptive variation. This thesis takes a
case-study approach and explores the issues surrounding these themes for conservation
strategies in two angiosperm species: Saxifraga hirculus and Lathyrus japonicus.
1) Protecting a broad spectrum of genetic biodiversity: This section of the thesis
considered the evidence for major intra-specific genetic races in Saxifraga hirculus and
the spatial distribution of its genetic biodiversity. Variation in Saxifraga hirculus
chloroplast DNA was assessed in order to gain information on the biogeography of the
British populations in the context of the wider European gene pool, and also to compare
this with populations from Alaska and Colorado. In a European context, British
popUlations have a high level of chloroplast diversity (three haplotypes) and contain a
highly divergent lineage that was previously unsuspected. Seven haplotypes were found
in total from 17 popUlations in Europe with marked inter-population differentiation (FST
= 0.92). Higher diversity and lower popUlation differentiation was detected in Alaska
(33 haplotypes /12 populations; FST = 0.46). Since most popUlations in Europe had
unique haplotypes it is not possible to track migration routes or pinpoint refugia for the
European popUlations, but the much higher diversity in Alaska compared to Europe
indicates that the Beringia region may have acted as a refugium for this species
throughout the Pleistocene. This highlights the importance of Alaska for the
conservation of intra-specific genetic biodiversity in this species.
(2) Evolutionary fitness and adaptive variation: To assess the relationship between
population size, genetic variation, morphological variation and fitness, genetic studies
were undertaken on populations of Lathyrusjaponicus. Eleven populations of L.
japonicus were examined for variation using nine microsatellite loci. The populations
show genetic isolation by distance across the distribution of the species in Britain,
although isolation by distance breaks down when only the range centre populations are
considered. There was no relationship between population size or isolation and genetic
variation, with some small and/or isolated populations having high diversity, and large
and/or range centre populations having low diversity. There was, however, a significant
difference in the inbreeding coefficient of adult versus seedling plants. The
heterozygosity of adult plants sampled in the field was significantly higher than
seedlings grown in cultivation, indicating a survival advantage for heterozygotes.
Significant differences were found between populations for seed weight, number of
seeds per pod, number of pods per cluster, and leaf shape of L. japonicus individuals in
the field. For seedlings grown in common conditions significant differences were found
in leaf shape, pigmentation, and dry weight after two season's growth. Morphological
and genetic differentiation were well matched in this species, and gave similar signals.
Seedlings from Carnoustie (Scotland) grew much more vigorously in cultivation in
Edinburgh than seedlings sourced from English populations, indicating local adaptation.
However no significant relationship was found between any fitness associated traits or
morphological variation with genetic variation, in spite of the heterozygote advantage
revealed by the genetic data.
The results from both research themes are discussed highlighting the difficulties in
equating patterns of genetic marker variation to traits likely to be of evolutionary and
ecological relevance.

Item Type: Thesis (PhD)
Qualification Level: Postdoctoral
Subjects: Q Science > QH Natural history > QH301 Biology
Colleges/Schools: College of Science and Engineering > School of Engineering > Infrastructure and Environment
Supervisor's Name: Hollingsworth, Doctor Pete and Sydes, Chris and Griffiths, Doctor Richard
Date of Award: May 2004
Depositing User: Mrs Marie Cairney
Unique ID: glathesis:2004-7087
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 11 Feb 2016 12:58
Last Modified: 11 Feb 2016 13:00

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