L'analyse électrophorétique de 15 populations sauvages (Marmota m. marmota) révèle un ancien goulot d'étranglement. Electrophoretic analysis of 15 wild marmot populations reveals an ancient bottle neck.

Résumé

Allozyme variation at 50 loci was studied in 15 populations of the alpine marmot (Marmota m. marmota). Four samples (1 from- Switzerland, 3 from the western part of Austria) represent autochthonous populations. The rest of the samples was taken from areas in the central and eastern part of Austria. These populations originale from repeated re-introduction efforts since 1860. Only 2 loci (Pep-1 and Sod-1) were found polymorphic. Average heterozygosity was 1.2%. No rare alleles could be detected. Autochthonous and re-introduced populations are genetically differentiated. Allele frequencies are more heterogenous among the non-autochthonous populations. At the Sod-1 locus there is a trend towards fixation of the fast allele. The polymorphisms at Pep-1 and Sod-1 are probably conserved by selective forces. In Pep-1 genotypes differ with respect to their degree of infestation by the endoparasites Citellina alpina and Ctenotaenia marmotae. No deviations from Hardy-Weinberg equilibrium were observed. The population structure is not affected by inbreeding. Diminished genetic variation, the absence of rare alleles, and the geographic pattern of the allele frequencies at the two variable loci can be best explained by a bottleneck after the last glaciation.