Loss of genetic variation in geographically marginal populations of Atriplex tatarica (Chenopodiaceae).
OBJECTIVE
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.


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.
Mandák
Bohumil
B
Institute of Botany, Academy of Sciences of the Czech Republic, CZ-252 43 Průhonice, Czech Republic. mandak@ibot.cas.cz
Bímová
Katerina
K
Placková
Ivana
I
Mahelka
Václav
V
Chrtek
Jindrich
J
D019663:Chenopodiaceae / Q000145:classification / Q000201:enzymology / Q000235:genetics*; D018153:Czech Republic; D005787:Gene Frequency; D014644:Genetic Variation / Q000235:genetics*; D005843:Geography; D007527:Isoenzymes / Q000235:genetics; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics; D011110:Polymorphism, Genetic / Q000235:genetics
D007527:Isoenzymes; D010940:Plant Proteins