Original Article

Heredity (2004) 93, 273–282. doi:10.1038/sj.hdy.6800500 Published online 23 June 2004

Genetic introgression between wild and stocked salmonids and the prospects for using molecular markers in population rehabilitation: the case of the Adriatic grayling (Thymallus thymallus L. 1785)

S Sus caronnik1,4, P Berrebi2, P Dovc caron1, M M Hansen3 and A Snoj1

  1. 1Biotechnical Faculty, Department of Animal Science, Groblje 3, SI-1230 Domz caronale, Slovenia
  2. 2Laboratoire Ecosystèmes Lagunaires, UMR CNRS-UM2 5119, Université Montpellier 2, cc093, 34095 Montpellier cedex 05, France
  3. 3Department of Inland Fisheries, Danish Institute for Fisheries Research, Vejlsøvej 39, DK-8600 Silkeborg, Denmark

Correspondence: A Snoj, Biotechnical Faculty, Department of Animal Science, Groblje 3, SI-1230 Domz caronale, Slovenia. E-mail: ales.snoj@bfro.uni-lj.si

4Current address: Agricultural Institute of Slovenia, Hacquetova 17, SI-1000 Ljubljana, Slovenia.

Received 23 May 2003; Accepted 7 April 2004; Published online 23 June 2004.

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Abstract

In the north Adriatic basin, a morphologically and genetically distinct lineage of grayling is found, designated as the Adriatic grayling. In Slovenia, the Adriatic grayling is restricted to the Soc carona river system, where it is critically endangered. The most pertinent threat is stocking with non-native, highly divergent Sava (Danubian) drainage stock, and this activity has been going on for more than four decades. The present study was designed to characterise the genetic structure of the Adriatic grayling in Slovenia, with particular emphasis on estimating the degree of introgression with non-indigenous stocked grayling. We analysed polymorphism at 154 microsatellite loci in samples representing grayling from the Adriatic and Danubian drainage stock. A relatively high number (12) of alleles, diagnostic for the Adriatic grayling, were identified. However, a correspondence analysis based on individual multilocus genotypes also revealed that there is no distinctive Adriatic group but rather a dispersed multitude of individuals that cannot be unambiguously distinguished from the more homogenous Danubian population. A Bayesian analysis of individual admixture coefficients confirmed this pattern and revealed extensive introgression between the Adriatic grayling and stocked grayling of Danubian origin. Average individual admixture coefficients showed that only between 50 and 60% of the original gene pools remained, and only few non-introgressed indigenous individuals could be identified. Microsatellite-based individual admixture analysis appear to be an important tool for identifying remaining non-introgressed indigenous individuals that could be used for restoring the original populations.

Keywords:

admixture analysis, Adriatic grayling, Thymallus thymallus, microsatellites, introgression, conservation