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Genetic structure in a fragmented Northern Hemisphere rainforest: large effective sizes and high connectivity among populations of the epiphytic lichen Lobaria pulmonaria

Authors

  • OLGA HILMO,

    1. Department of Biology, Faculty of Natural Science and Technology, Norwegian University of Science and Technology, N–7491 Trondheim, Norway
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  • SVERRE LUNDEMO,

    1. Department of Biology, Faculty of Natural Science and Technology, Norwegian University of Science and Technology, N–7491 Trondheim, Norway
    2. Systematics and Evolution Group, Section of Natural History, Museum of Natural History and Archaeology, Norwegian University of Science and Technology, N–7491 Trondheim, Norway
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  • HÅKON HOLIEN,

    1. Faculty of Agriculture and Information Technology, Nord-Trøndelag University College, Servicebox 2501, N–7729 Steinkjer, Norway
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  • KIRSTI STENGRUNDET,

    1. Department of Biology, Faculty of Natural Science and Technology, Norwegian University of Science and Technology, N–7491 Trondheim, Norway
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  • HANS K. STENØIEN

    1. Systematics and Evolution Group, Section of Natural History, Museum of Natural History and Archaeology, Norwegian University of Science and Technology, N–7491 Trondheim, Norway
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Olga Hilmo, Fax: +47 73596100; E-mail: olga.hilmo@bio.ntnu.no

Abstract

An extraordinary diversity of epiphytic lichens is found in the boreal rainforest of central Norway, the highest-latitude rainforest in the world. These rainforest relicts are located in ravine systems, and clear cutting has increased the distance between remaining patches. We hypothesized that the relatively small lichen populations in the remaining forest stands have suffered a depletion of genetic diversity through bottlenecks and founder events. To test this hypothesis, we assessed genetic diversity and structure in the populations of the tripartite lichen Lobaria pulmonaria using eight SSR loci. We sampled thalli growing on Picea abies branches and propagules deposited in snow at three localities. Contrary to expectations, we found high genetic diversity in lichen and snow samples, and high effective sizes of the studied populations. Also, limited genetic differentiation between populations, high historical migration rates, and a high proportion of first generation immigrants were estimated, implying high connectivity across distances <30 km. Almost all genetic variation was attributed to variation within sites; spatial genetic structures within populations were absent or appeared on small scales (5–10 m). The high genetic diversity in the remaining old boreal rainforests shows that even relict forest patches might be suitable for conservation of genetic diversity.

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