Funding Information This research was made possible by funding from the National Sciences and Engineering Research Council of Canada discovery grants to J. B. (strategic grant #321969 and discovery grant #46273).
Large-scale asymmetric introgression of cytoplasmic DNA reveals Holocene range displacement in a North American boreal pine complex
Article first published online: 6 JUL 2012
© 2012 The Authors. Ecology and Evolution published by Blackwell Publishing Ltd.
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Ecology and Evolution
Volume 2, Issue 8, pages 1853–1866, August 2012
How to Cite
Godbout, J., Yeh, F. C. and Bousquet, J. (2012), Large-scale asymmetric introgression of cytoplasmic DNA reveals Holocene range displacement in a North American boreal pine complex. Ecology and Evolution, 2: 1853–1866. doi: 10.1002/ece3.294
- Issue published online: 6 AUG 2012
- Article first published online: 6 JUL 2012
- Manuscript Accepted: 9 MAY 2012
- Manuscript Revised: 8 MAY 2012
- Manuscript Received: 24 JAN 2012
- National Sciences and Engineering Research Council of Canada. Grant Numbers: #321969, #46273
- Chloroplast DNA;
- hybrid zone;
- mitochondrial DNA;
- Pinus banksiana ;
- Pinus contorta
Jack pine ( Pinus banksiana) and lodgepole pine ( Pinus contorta var. latifolia) are two North American boreal hard pines that hybridize in their zone of contact in western Canada. The main objective of this study was to characterize their patterns of introgression resulting from past and recent gene flow, using cytoplasmic markers having maternal or paternal inheritance. Mitochondrial DNA (mtDNA) and chloroplast DNA (cpDNA) diversity was assessed in allopatric populations of each species and in stands from the current zone of contact containing morphological hybrids. Cluster analyses were used to identify genetic discontinuities among groups of populations. A canonical analysis was also conducted to detect putative associations among cytoplasmic DNA variation, tree morphology, and site ecological features. MtDNA introgression was extensive and asymmetric: it was detected in P. banksiana populations from the hybrid zone and from allopatric areas, but not in P. contorta populations. Very weak cpDNA introgression was observed, and only in P. banksiana populations. The mtDNA introgression pattern indicated that central Canada was first colonized by migrants from a P. contorta glacial population located west of the Rocky Mountains, before being replaced by P. banksiana migrating westward during the Holocene. In contrast, extensive pollen gene flow would have erased the cpDNA traces of this ancient presence of P. contorta. Additional evidence for this process was provided by the results of canonical analysis, which indicated that the current cpDNA background of trees reflected recent pollen gene flow from the surrounding dominant species rather than historical events that took place during the postglacial colonization.