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Molecular footprints of the H olocene retreat of dwarf birch in B ritain
Author(s) -
Wang Nian,
Borrell James S.,
Bodles William J. A.,
Kuttapitiya Anasuya,
Nichols Richard A.,
Buggs Richard J. A.
Publication year - 2014
Publication title -
molecular ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.619
H-Index - 225
eISSN - 1365-294X
pISSN - 0962-1083
DOI - 10.1111/mec.12768
Subject(s) - introgression , biology , range (aeronautics) , cline (biology) , ecology , polyploid , ploidy , botany , genetics , population , materials science , demography , sociology , gene , composite material
Past reproductive interactions among incompletely isolated species may leave behind a trail of introgressed alleles, shedding light on historical range movements. B etula pubescens is a widespread native tetraploid tree species in B ritain, occupying habitats intermediate to those of its native diploid relatives, B . pendula and B . nana . Genotyping 1134 trees from the three species at 12 microsatellite loci, we found evidence of introgression from both diploid species into B . pubescens , despite the ploidy difference. Surprisingly, introgression from B . nana , a dwarf species whose present range is highly restricted in northern, high‐altitude peat bogs, was greater than introgression from B . pendula , which is morphologically similar to B . pubescens and has a substantially overlapping range. A cline of introgression from B . nana was found extending into B . pubescens populations far to the south of the current B . nana range. We suggest that this genetic pattern is a footprint of a historical decline and/or northwards shift in the range of B . nana populations due to climate warming in the Holocene. This is consistent with pollen records that show a broader, more southerly distribution of B . nana in the past. Ecological niche modelling predicts that B . nana 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 B . nana and B . pendula , despite both being diploid, perhaps because their distributions in the past have rarely overlapped. Future conservation of B . nana may partly depend on minimization of hybridization with B . pubescens , and avoidance of planting B . pendula near B . nana populations.