Partenaires et organisations internationales
(Anglais)
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LMU (München), FBUA (Wien), BOKU (Wien), LIECO (Kalwang), INRA (Avignon), LSP (Teisendorf), BFH (Hamburg), Università di Udine (Udine), CNR (Florenz), Université de Neuchâtel (Neuchâtel)
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Résumé des résultats (Abstract)
(Anglais)
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Biodiversity cannot only be assessed at the species level, but also as genetic variation within and between popu-lations. Both levels need to be considered when decisions are made about the conservational value of species or populations. Within the framework of the present project, the genetic diversity of the five major tree species in Alpine forests are studied. The in-volved partners analyze genetic markers of all three genomes (nuclear, chloro-plast, mitochondrial). The various markers allow to ad-dress specific questions in relation to population genetics. Multilocus genotypes of approx. 30'000 trees elucidate the genetic population structure, population differen-tiation, gene exchange, and the adaptation potential of Alpine forest ecosystems.
At WSL, we are mainly concerned with detecting genetic variation in the maternally transmitted mitochondrial DNA (mtDNA) of Nor-way spruce (Picea abies) and Swiss stone pine (Pinus cembra). An internal fragment of nad1 intron 2, which has been shown to vary across the distributional range of Norway spruce, was used for determining variation within and between populations of the two investigated species. Plant material was collec-ted by the project partners at 13 transects throughout the Alps. Each transect consisted of three elevational le-vels, the uppermost located at or near the treeline. In addition, three intensively studied plots (ISPs) have been established, in which small-scale population dynamics are studied.
The sampled Norway spruce populations of France and Switzerland as well as most German and Austrian popu-lations showed no variation in the mtDNA nad1 intron, whereas few of the German, Austrian, and almost all Italian po-pu-lations were variable. This results in a significant differentiation between western and eastern Alpine regions (FST = 0.41. P < 0.05). We relate this pattern to postglacial re-colonization pathways. The monomorphic west-ern Alpine populations are assumed to result from one or several founder effects during immigration of Norway spruce from its putative central European refugium. The high genetic variation found in one of the Italian transects is at-tri-buted to either a contact of different re-immigration routes and/or the proximity to the putative refugia. Haplo-typic diversity was similar at high- compared with low-elevation populations in the genetically variable transects. Our hypothesis that colonization occurred from low to high elevations, resulting in a limited number of success-fully established haplotypes at high-elevation populations, could thus not be confirmed. This finding was in accor-dance with results from other genetic markers.
In Swiss stone pine, including samples from the closely related Pinus sibirica, the same mtDNA marker proved to be monomorphic. Screening of additionally available mtDNA markers confirmed both intra- and interspecific mo-no-morphy. Only chloroplast microsatellites and nuclear isozymes, analyzed by project partners, revealed a pattern of genetic variation, which was in agreement with the east-west gradient already observed in Norway spruce mtDNA.
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