Canadian Forest Service Publications
Contrasting patterns of genetic diversity across the ranges of Pinus monticola and P. strobus: a comparison between eastern and western North American postglacial colonization histories. 2015. Nadeau, S.; Godbout, J.; Lamothe, M.; Gros-Louis, M.-C.; Isabel, N.; Ritland, K. Am. J. Bot. 102(8) 1342-1355.
Available from: Laurentian Forestry Centre
Catalog ID: 36218
CFS Availability: PDF (request by e-mail)
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• Premises of the study: Understanding the influence of recent glacial and postglacial periods on species’ distributions is key for predicting the effects of future environmental changes. We investigated the influence of two physiographic landscapes on population structure and postglacial colonization of two white pine species of contrasting habitats: P. monticola, which occurs in the highly mountainous region of western North America, and P. strobus, which occurs in a much less mountainous area in eastern North America.
• Methods: To characterize the patterns of genetic diversity and population structure across the ranges of both species, 158 and 153 single nucleotide polymorphism (SNP) markers derived from expressed genes were genotyped on range-wide samples of 61 P. monticola and 133 P. strobus populations, respectively.
• Key results: In P. monticola, a steep latitudinal decrease in genetic diversity likely resulted from postglacial colonization involving rare long-distance dispersal (LDD) events. In contrast, no geographic patterns of diversity were detected in P. strobus, suggesting recolonization via a gradually advancing front or frequent LDD events. For each species, STRUCTURE analyses identified two distinct southern and northern genetic groups that likely originated from two different glacial lineages. At a finer scale, and for the two species, smaller subgroups were detected that could be remnants of cryptic refugia.
• Conclusion: During postglacial colonization, the western and eastern North American landscapes had different impacts on genetic signatures in P. monticola compared with P. strobus. We discuss the importance of our findings for conservation programs and predictions of species’ response to climate change.
Plain Language Summary
In this study, the researchers demonstrated that the presence of natural barriers (mountain ranges) has influenced western white pine recolonization processes since the last ice age and, consequently, the genetic diversity of the species. Western white pine is found mainly in the mountainous regions of western North America. A significant decrease in the genetic diversity of this species has been observed in northern areas. This attests to a recolonization process that involves rare events of seed dispersal over great distances. Such events would have allowed western white pine to cross natural barriers.
Conversely, eastern white pine, which grows in less mountainous regions of eastern North America, appears to have been little influenced during its recolonization by the presence of natural barriers. Instead, the high levels of genetic diversity throughout the distribution range of eastern white pine suggest that this species has gradually extended its distribution range.
For both species, the researchers also observed two genetically distinct groups as well as sub groups within each group. These various sub groups indicate the presence of several refugia during the last ice age. These findings will be used to make adjustments to genetic diversity conservation programs, and will be helpful in predicting the effects of future climate conditions on western white pine and eastern white pine populations.
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