Question: Can genetic tools combined with phytogeography help to define local plants and how geographically close the source population should be to the restoration site? Location: Subalpine and alpine French Pyrenees. Methods: The main phytogeographic boundaries in the French Pyrenees described by different authors were studied and this geographic pattern was compared with the results of genetic analysis for the four Pyrenean plants studied (Trifolium alpinum, Festuca eskia, Festuca gautieri and Rumex scutatus), based on random amplified polymorphic DNA (RAPD) marker analysis, unweighted pair-group method with arithmetic averages (UPGMA) analysis and Mantel correlograms comparing geographic and genetic distances. Results: The genetic analysis allowed definition of two main evolutionarily significant units (ESUs) for the plants under study. Although the limit between the two zones was slightly variable according to the species considered, an eastern and a western ESU was consistently observed. This delineation was concordant with the main phytogeographic boundaries of the French Pyrenees. Conclusion: RAPD markers and associated Mantel correlograms can be useful to draw ESUs for individual species when the sampling intensity is relatively dense, and similarities were revealed between species sharing the same distribution range. This delineation allowed integration of infraspecific plant variation in the management of natural resources for revegetation in the Pyrenees. Nevertheless, caution is needed for the establishment of seed pools in order to maximize genetic diversity in each of the pools during collection and production.

Background and aimsAster pyrenaeus (Asteraceae) is an endangered species, endemic to the Pyrenees and Cantabrian Mountain ranges (Spain). For its long-term persistence, this taxon needs an appropriate conservation strategy to be implemented. In this context, we studied the genetic structure over the entire geographical range of the species and then inferred the genetic relationships between populations.MethodologyMolecular diversity was analysed for 290 individuals from 12 populations in the Pyrenees and the Cantabrian Mountains using inter simple sequence repeats (ISSRs). Bayesian-based analysis was applied to examine population structure.Principal resultsAnalysis of genetic similarity and diversity, based on 87 polymorphic ISSR markers, suggests that despite being small and isolated, populations have an intermediate genetic diversity level (P % = 52.8 %, HE = 0.21 ± 0.01, genetic similarity between individuals = 49.6 %). Genetic variation was mainly found within populations (80–84 %), independently of mountain ranges, whereas 16–18 % was found between populations and <5 % between mountain ranges. Analyses of molecular variance indicated that population differentiation was highly significant. However, no significant correlation was found between the genetic and geographical distances among populations (Rs = 0.359, P = 0.140). Geographical structure based on assignment tests identified five different gene pools that were independent of any particular structure in the landscape.ConclusionsThe results suggest that population isolation is probably relatively recent, and that the outbreeding behaviour of the species maintains a high within-population genetic diversity. We assume that some long-distance dispersal, even among topographically remote populations, may be determinant for the pattern of genetic variation found in populations. Based on these findings, strategies are proposed for genetic conservation and management of the species.

Abstract.-Trifolium alpinum L. is an important component of the high-elevated grazing ecosystem in the French Pyrenees. To assess population relationships and levels of geographical differentiation of it in this region, we analysed forty populations sampled in ten river catchments by RAPD. Our results indicated intermediate level of genetic diversity in most populations, most of it being attributed to intrapopulation variation after AMOVA. Population differentiation evaluated through F ST and exact tests showed that an important genetic differentiation exists among populations. This differentiation is to some extent explained by the occurrence of two divergent groups along the massif that distinguish an eastern and a western pool of T. alpinum populations. Paleoclimatic episodes of the Quaternary, involving altitudinal species migration from glacial refugia, could explain the pattern of neutral diversity observed. Additional factors such as adaptative divergence or species life traits are proposed to explain the maintenance of this pattern through time.Key words : altitudinal migration -genetic diversity -mountain flora -phylogeography -population structure -quaternary glaciations.Résumé.-Trifolium alpinum L. est une composante importante des pâturages du versant français des Pyrénées. Pour évaluer les relations entre les populations et son niveau de différenciation génétique dans cette région, nous avons analysé quarante populations issues de dix bassins versants à l'aide de marqueurs neutres RAPD. Nos résultats indiquent des niveaux moyens de diversité génétique dans la plupart des populations étudiées, dont la plus grande partie est attribuée à une variation intrapopulation. La différenciation évaluée par le F ST et par tests exacts montre qu'il existe une importante différenciation entre les populations, qui s'explique en partie par l'existence de deux groupes distincts le long du massif séparant les populations de T. alpinum de l'est de la chaîne de celles de l'ouest. Les épisodes paléoclimatiques du Quaternaire, incluant des migrations altitudinales d'espèces depuis des refuges glaciaires, pourraient expliquer la structuration de la diversité neutre observée. Des facteurs complé-mentaires, comme une divergence adaptative ou les traits de vie de l'espèce, peuvent expliquer la conservation de cette structuration jusqu'à nos jours.Mots clés : migration altitudinale -diversité génétique -flore orophile -phylogéographie -structuration des populations -glaciations quaternaires.

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