TY - JOUR
T1 - Phylogeography of Douglas-fir based on mitochondrial and chloroplast DNA sequences
T2 - Testing hypotheses from the fossil record
AU - Gugger, Paul F.
AU - Sugita, Shinya
AU - Cavender-Bares, Jeannine
PY - 2010/5
Y1 - 2010/5
N2 - The integration of fossil and molecular data can provide a synthetic understanding of the ecological and evolutionary history of an organism. We analysed range-wide maternally inherited mitochondrial DNA and paternally inherited chloroplast DNA sequence data with coalescent simulations and traditional population genetic methods to test hypotheses of population divergence generated from the fossil record of Douglas-fir (Pseudotsuga menziesii), an ecologically and economically important western North American conifer. Specifically, we tested (i) the hypothesis that the Pliocene orogeny of the Cascades and Sierra Nevada caused the divergence of coastal and Rocky Mountain Douglas-fir varieties; and (ii) the hypothesis that multiple glacial refugia existed on the coast and in the Rocky Mountains. We found that Douglas-fir varieties diverged about 2.11 Ma (4.37 Ma-755 ka), which could be consistent with a Pliocene divergence. Rocky Mountain Douglas-fir probably resided in three or more glacial refugia. More variable molecular markers would be required to detect the two coastal refugia suggested in the fossil record. Comparison of mitochondrial DNA and chloroplast DNA variation revealed that gene flow via pollen linked populations isolated from seed exchange. Postglacial colonization of Canada from coastal and Rocky Mountain refugia near the ice margin at the Last Glacial Maximum produced a wide hybrid zone among varieties that formed almost exclusively by pollen exchange and chloroplast DNA introgression, not seed exchange. Postglacial migration rates were 50-165 m/year, insufficient to track projected 21st century warming in some regions. Although fossil and genetic data largely agree, each provides unique insights.
AB - The integration of fossil and molecular data can provide a synthetic understanding of the ecological and evolutionary history of an organism. We analysed range-wide maternally inherited mitochondrial DNA and paternally inherited chloroplast DNA sequence data with coalescent simulations and traditional population genetic methods to test hypotheses of population divergence generated from the fossil record of Douglas-fir (Pseudotsuga menziesii), an ecologically and economically important western North American conifer. Specifically, we tested (i) the hypothesis that the Pliocene orogeny of the Cascades and Sierra Nevada caused the divergence of coastal and Rocky Mountain Douglas-fir varieties; and (ii) the hypothesis that multiple glacial refugia existed on the coast and in the Rocky Mountains. We found that Douglas-fir varieties diverged about 2.11 Ma (4.37 Ma-755 ka), which could be consistent with a Pliocene divergence. Rocky Mountain Douglas-fir probably resided in three or more glacial refugia. More variable molecular markers would be required to detect the two coastal refugia suggested in the fossil record. Comparison of mitochondrial DNA and chloroplast DNA variation revealed that gene flow via pollen linked populations isolated from seed exchange. Postglacial colonization of Canada from coastal and Rocky Mountain refugia near the ice margin at the Last Glacial Maximum produced a wide hybrid zone among varieties that formed almost exclusively by pollen exchange and chloroplast DNA introgression, not seed exchange. Postglacial migration rates were 50-165 m/year, insufficient to track projected 21st century warming in some regions. Although fossil and genetic data largely agree, each provides unique insights.
KW - Coalescent simulations
KW - Glacial refugia
KW - Introgression
KW - Isolation with migration
KW - Mutation rate
KW - Postglacial migration
KW - Pseudotsuga menziesii
KW - Samova
UR - http://www.scopus.com/inward/record.url?scp=77951195956&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=77951195956&partnerID=8YFLogxK
U2 - 10.1111/j.1365-294X.2010.04622.x
DO - 10.1111/j.1365-294X.2010.04622.x
M3 - Article
C2 - 20374486
AN - SCOPUS:77951195956
SN - 0962-1083
VL - 19
SP - 1877
EP - 1897
JO - Molecular ecology
JF - Molecular ecology
IS - 9
ER -