AOBPreview originally published online on August 17, 2005
Annals of Botany 2005 96(5):901-912; doi:10.1093/aob/mci242
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Loss of Genetic Variation in Geographically Marginal Populations of Atriplex tatarica (Chenopodiaceae)
INA BÍMOVÁ1,2
KOVÁ1ICH CHRTEK1
1 Institute of Botany, Academy of Sciences of the Czech Republic, CZ-252 43 Pr
honice, Czech Republic and 2 Institute of Applied Ecology, Czech Agricultural University Prague, CZ-281 63 Kostelec nad ern
mi lesy, Czech Republic
* For correspondence. E-mail mandak{at}ibot.cas.cz
Received: 14 January 2005 Returned for revision: 25 April 2005 Accepted: 22 June 2005 Published electronically: 17 August 2005
• Background and Aims Genetic variability was estimated for Atriplex tatarica from 25 populations in the Czech Republic. Since its north-western range margin is in central Europe, a relationship between marginality and low within-population genetic diversity was tested in accordance with the Central–Marginal Model.
• Methods Population genetic diversity was expressed by assessing patterns of variation at 13 putatively neutral allozyme loci (comprising 30 putative alleles) within and between 25 natural populations of A. tatarica along a north-west–south-east transect in the Czech Republic.
• Key Results Atriplex tatarica is a species of human-made habitats with a mixed mating system and wide geographic distribution. Overall, A. tatarica displayed moderate levels of genetic diversity in comparison with other herbaceous plants. The percentage of loci that were polymorphic was 47·1 %, with average values of 1·55, 0·151 and 0·155 for the average number of alleles per polymorphic locus (A), observed heterozygosity (Ho) and expected heterozygosity (He), respectively. There was only weak evidence of inbreeding within populations (FIS = 0·031) and significant population differentiation (FST = 0·214). Analysis of the data provides no evidence for isolation-by-distance for the whole study area. However, Mantel tests were highly significant for the marginal Bohemian region and non-significant for the central Moravian region. While northern populations of A. tatarica showed significantly lower allelic richness (A = 1·462) than populations from the southern part of the study area (A = 1·615), they did not differ in observed heterozygosity (Ho), gene diversity (HS), inbreeding within populations (FIS) or population differentiation (FST), despite generally lower values of particular genetic measurements in the marginal region.
• Conclusions Genetic diversity, with the exception of allelic richness, was not significantly lower at the margins of the species' range. This, therefore, provides only weak support for the predictions of the Central–Marginal Model.
Key words: Allozyme, Atriplex, Central–Marginal Model, Chenopodiaceae, founder effect, inbreeding, invasion, population genetic structure
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