MBE Advance Access originally published online on January 30, 2006
Molecular Biology and Evolution 2006 23(4):807-816; doi:10.1093/molbev/msj100
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Published by Oxford University Press 2006.
Research Article |
Genetic Structure and Evolutionary History of a Diploid Hybrid Pine Pinus densata Inferred from the Nucleotide Variation at Seven Gene Loci
* State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing, China; and Department of Biology, Graduate School of Science, Kyushu University, Fukuoka, Japan
E-mail: xiao-ru.wang{at}niwl.se.
Although homoploid hybridization is increasingly recognized as an important phenomenon in plant evolution, its evolutionary genetic mechanisms are poorly documented and understood. Pinus densata, a pine native to the Tibetan Plateau, represents a good example of a homoploid hybrid speciation facilitated by adaptation to extreme environment and ecological isolation from the parents. Its ecologically and reproductively stabilized nature offers excellent opportunity for studying genetic processes associated with hybrid speciation. In this study, we investigated the levels and patterns of nucleotide variation in P. densata and its putative parents. Haplotype composition, gene genealogies, and the levels and patterns of nucleotide variation gave further support to the hybrid nature of P. densata. Allelic history, as revealed by our data, suggests the ancient nature of the hybrid preceding elevation of the Tibetan Plateau. We detected more deviations from neutrality in P. densata than in the parental species. Thus, at least some of the evolutionary forces that have shaped the genetic variation in P. densata are likely to be different from those acting upon parental species. We speculate that when populations of P. densata invaded new territories, they had elevated rates of response to selection in order to develop traits that help them to survive and adapt in the new environments.
Key Words: genealogy • hybrid speciation • nucleotide polymorphism • Pinus densata • population heterogeneity • selection
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