Genetic effects of chronic habitat fragmentation on tree species: the case of Sorbus aucuparia in a deforested Scottish landscape

Authors

  • C. F. E. Bacles,

    Corresponding author
    1. Institute of Cell, Animal and Population Biology, Ashworth Laboratories, School of Biological Sciences, University of Edinburgh, Edinburgh, EH9 3JT, UK,
    2. Centre for Ecology and Hydrology-Edinburgh, Bush Estate, Penicuik, Midlothian, EH26 0QB, UK,
      Cecile Bacles. Fax: 0131 4453943; E-mail: cfb@ceh.ac.uk
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  • A. J. Lowe,

    1. Centre for Ecology and Hydrology-Edinburgh, Bush Estate, Penicuik, Midlothian, EH26 0QB, UK,
    2. School of Life Sciences, University of Queensland, Brisbane, Qld., 4072, Australia
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  • R. A. Ennos

    1. Institute of Cell, Animal and Population Biology, Ashworth Laboratories, School of Biological Sciences, University of Edinburgh, Edinburgh, EH9 3JT, UK,
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Cecile Bacles. Fax: 0131 4453943; E-mail: cfb@ceh.ac.uk

Abstract

Sustainable forest restoration and management practices require a thorough understanding of the influence that habitat fragmentation has on the processes shaping genetic variation and its distribution in tree populations. We quantified genetic variation at isozyme markers and chloroplast DNA (cpDNA), analysed by polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP) in severely fragmented populations of Sorbus aucuparia (Rosaceae) in a single catchment (Moffat) in southern Scotland. Remnants maintain surprisingly high levels of gene diversity (HE) for isozymes (HE = 0.195) and cpDNA markers (HE = 0.490). Estimates are very similar to those from non-fragmented populations in continental Europe, even though the latter were sampled over a much larger spatial scale. Overall, no genetic bottleneck or departures from random mating were detected in the Moffat fragments. However, genetic differentiation among remnants was detected for both types of marker (isozymes Θn = 0.043, cpDNA Θc = 0.131; G-test, P-value < 0.001). In this self-incompatible, insect-pollinated, bird-dispersed tree species, the estimated ratio of pollen flow to seed flow between fragments is close to 1 (r = 1.36). Reduced pollen-mediated gene flow is a likely consequence of habitat fragmentation, but effective seed dispersal by birds is probably helping to maintain high levels of genetic diversity within remnants and reduce genetic differentiation between them.

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