Molecular footprints of the Holocene retreat of dwarf birch in Britain. Issue 11 (16th May 2014)

• Record Type: Journal Article
• Authors: Wang, Nian; Borrell, James S.; Bodles, William J. A.; Kuttapitiya, Anasuya; Nichols, Richard A.; Buggs, Richard J. A.
• Is Part Of: Molecular ecology. Volume 23:Issue 11(2014)
• Page Start: 2771
• Page End: 2782
• Publication Date: 2014-05-16
• Subjects: Molecular ecology -- Periodicals; Molecular population biology -- Periodicals; 576
• DOI: 10.1111/mec.12768
• Languages: English
• ISSNs: 0962-1083

Abstract

<abstract abstract-type="main" id="mec12768-abs-0001"> <title>Abstract</title> <p>Past reproductive interactions among incompletely isolated species may leave behind a trail of introgressed alleles, shedding light on historical range movements. <italic>Betula pubescens</italic> is a widespread native tetraploid tree species in Britain, occupying habitats intermediate to those of its native diploid relatives, <italic>B. pendula</italic> and <italic>B. nana</italic>. Genotyping 1134 trees from the three species at 12 microsatellite loci, we found evidence of introgression from both diploid species into <italic>B. pubescens</italic>, despite the ploidy difference. Surprisingly, introgression from <italic>B. nana</italic>, a dwarf species whose present range is highly restricted in northern, high‐altitude peat bogs, was greater than introgression from <italic>B. pendula</italic>, which is morphologically similar to <italic>B. pubescens</italic> and has a substantially overlapping range. A cline of introgression from <italic>B. nana</italic> was found extending into <italic>B. pubescens</italic> populations far to the south of the current <italic>B. nana</italic> range. We suggest that this genetic pattern is a footprint of a historical decline and/or northwards shift in the range of <italic>B. nana</italic> populations due to climate warming in the Holocene. This is consistent with pollen records that show a broader, more southerly distribution of <italic>B. nana</italic> in the past. Ecological niche modelling predicts that <italic>B. nana</italic> is adapted to a larger range than it currently occupies, suggesting additional factors such as grazing and hybridization may have exacerbated its decline. We found very little introgression between <italic>B. nana</italic> and <italic>B. pendula</italic>, despite both being diploid, perhaps because their distributions in the past have rarely overlapped. Future conservation of <italic>B. nana</italic> may partly depend on minimization of hybridization with <italic>B. pubescens</italic>, and avoidance of planting <italic>B. pendula</italic> near <italic>B. nana</italic> populations.</p> </abstract>