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Landscape effects on extremely fragmented populations of a rare solitary bee, Colletes floralis

Authors

  • EMILY S. DAVIS,

    1. School of Biological Sciences, Queen’s University Belfast, 97 Lisburn Rd., Belfast BT9 7BL, UK
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  • TOMÁS E. MURRAY,

    1. School of Biological Sciences, Queen’s University Belfast, 97 Lisburn Rd., Belfast BT9 7BL, UK
    2. Crops Research Centre, Teagasc, Oak Park, Carlow, Co. Carlow, Ireland
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  • ÚNA FITZPATRICK,

    1. Department of Zoology, School of Natural Sciences, Trinity College Dublin, Dublin 2, Ireland
    2. National Biodiversity Data Centre, Beechfield House, WIT West Campus, Carriganore, Waterford, Ireland
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  • MARK J. F. BROWN,

    1. Department of Zoology, School of Natural Sciences, Trinity College Dublin, Dublin 2, Ireland
    2. School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey, TW20 0EX, UK
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  • ROBERT J. PAXTON

    1. School of Biological Sciences, Queen’s University Belfast, 97 Lisburn Rd., Belfast BT9 7BL, UK
    2. Institut für Biologie, Martin-Luther Universität Halle-Wittenberg, D-06099 Halle (Saale), Germany
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Emily S. Davis, Fax: +44 (0)28 90975877; E-mail: edavis01@qub.ac.uk

Abstract

Globally, there is concern over the decline of bees, an ecologically important group of pollinating insects. Genetic studies provide insights into population structure that are crucial for conservation management but that would be impossible to obtain by conventional ecological methods. Yet conservation genetic studies of bees have primarily focussed on social species rather than the more species-rich solitary bees. Here, we investigate the population structure of Colletes floralis, a rare and threatened solitary mining bee, in Ireland and Scotland using nine microsatellite loci. Genetic diversity was surprisingly as high in Scottish (Hebridean island) populations at the extreme northwestern edge of the species range as in mainland Irish populations further south. Extremely high genetic differentiation among populations was detected; multilocus FST was up to 0.53, and inline image and Dest were even higher (maximum: 0.85 and 1.00, respectively). A pattern of isolation by distance was evident for sites separated by land. Water appears to act as a substantial barrier to gene flow yet sites separated by sea did not exhibit isolation by distance. C. floralis populations are extremely isolated and probably not in regional migration-drift equilibrium. GIS-based landscape genetic analysis reveals urban areas as a potential and substantial barrier to gene flow. Our results highlight the need for urgent site-specific management action to halt the decline of this and potentially other rare solitary bees.

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