Articles by Tomas Roslin

Populations at species’ range margins are expected to show lower genetic diversity than populations at the core of the range. Yet, long-lived, widespread tree species are expected to be resistant to genetic impoverishment, thus showing comparatively high genetic diversity within populations and low differentiation among populations. Here, we study the distribution of genetic variation in the pedunculate oak (Quercus robur L.) at its range margin in Finland at two hierarchical scales using 15 microsatellite loci. At a regional scale, we compared variation within versus among three oak populations. At a landscape scale, we examined genetic structuring within one of these populations, growing on an island of ca 5 km². As expected, we found the majority of genetic variation in Q. robur to occur within populations. Nonetheless, differentiation among populations was markedly high (F_ST = 0.12) compared with values reported for populations of Q. robur closer to the core of its range. At the landscape level, some spatial and temporal sub-structuring was observed, likely explained by the history of land-use on the island. Overall, Q. robur fulfils the expectation of the central-marginal hypothesis of high differentiation among marginal populations, but the notable population differentiation has most likely been influenced also by the long, ongoing fragmentation of populations. Finnish oak populations may still be adjusting to the drastic habitat changes of the past centuries. Preservation of genetic variation within the remaining stands is thus an important factor in the conservation of Q. robur at its range margin.

• Pohjanmies, University of Helsinki, Department of Agricultural Sciences, Spatial Foodweb Ecology Group, P.O. Box 27, FI-00014 University of Helsinki, Finland; University of Jyväskylä, Department of Biological and Environmental Sciences, P.O. Box 35, FI-40014 University of Jyväskylä, Finland E-mail: tahti.t.pohjanmies@jyu.fi
• Elshibli, Natural Resources Institute Finland (Luke), Green technology, P.O. Box 18, FI-01301 Vantaa, Finland; University of Helsinki, Department of Agricultural Sciences, P.O. Box 27, FI-00014 University of Helsinki, Finland E-mail: sakina.elshibli@helsinki.fi
• Pulkkinen, Natural Resources Institute Finland (Luke), Green technology, Haapastensyrjäntie 34, FI-12600 Läyliäinen, Finland E-mail: pertti.pulkkinen@luke.fi
• Rusanen, Natural Resources Institute Finland (Luke), Green technology, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: mari.rusanen@luke.fi
• Vakkari, Natural Resources Institute Finland (Luke), Green technology, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: pekka.vakkari@luke.fi
• Korpelainen, University of Helsinki, Department of Agricultural Sciences, P.O. Box 27, FI-00014 University of Helsinki, Finland E-mail: helena.korpelainen@helsinki.fi
• Roslin, University of Helsinki, Department of Agricultural Sciences, Spatial Foodweb Ecology Group, P.O. Box 27, FI-00014 University of Helsinki, Finland; Swedish University of Agricultural Sciences, Department of Ecology, P.O. Box 7044, SE-750 07 Uppsala, Sweden E-mail: tomas.roslin@helsinki.fi