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Title: Spatial distribution of neutral & adaptive genetic diversity in populations of the palmate newt, Lissotriton helveticus
Author: Murray-Dickson, Gillian
ISNI:       0000 0004 2717 0982
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2011
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Conservation genetics theory predicts that isolated populations on the periphery of a species range will display reduced levels of genetic diversity compared to those more centrally located. Low levels of diversity can potentially compromise individual fitness and population viability among peripheral populations and so from a conservation perspective, understanding genetic structure among populations with low levels of diversity is a priority. Here I examine the levels and spatial distribution of both neutral and adaptive DNA polymorphisms across populations of the palmate newt (Lissotriton helveticus); including both island and mainland populations at the northern extent of their distribution and putative source populations from which postglacial expansion occurred. Five different classes of molecular marker were assayed: (1) mitochondrial DNA sequence variation, (2) micro satellite length variation, (3) MHC allelic diversity, (4) AFLP profiling and (5) candidate nuclear locus (sodium-calcium exchanger) allelic diversity, with an overall prediction that neutral markers will exhibit reducing diversity with increasing latitude and then from mainland to island; and that neutral diversity will be a poor predictor for adaptive diversity given the additional effects of selection on these genes. These predictions were not wholly confirmed. Mitochondrial data demonstrated that refugial populations harboured more genetic diversity than postglacial populations. Conversely, micro satellite diversity did not decline gradually with increasing latitude and insular populations were not necessarily depauperate compared to those on the mainland. Adaptive diversity was not reduced among peripheral or island populations but a signature of directional selection was detected. Lastly, genome-wide AFLP diversity was not reduced among island populations whilst no clear inference was possible from the sodium-calcium exchanger gene. There was a lack of concurrence between neutral and adaptive markers and the results are discussed in relation to the effects of micro-evolutionary processes acting in populations of varying size and isolation. The significance of these findings is discussed in relation to the long term conservation of palmate newt populations.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Newts ; Population genetics