title: Phylogenetic and Taxonomic Status Analyses of the Abaso Section from Multiple Nuclear Genes and Plastid Fragments Reveal New Insights into the North America Origin ofPopulus(Salicaceae).
abstract: Although, the Abaso section is widely accepted as an independent section, the taxonomic status ofPopulus mexicana(section Abaso) has not yet been resolved due to the limited availability markers and/or the lack ofP. mexicanaspecimens in previous studies. Thirty-one poplar species that represent six sections of thePopulusgenus were sampled, and 23 single-copy nuclear DNA and 34 chloroplast fragments were sequenced. The present study obtained two updated phylogenies ofPopulus. We found that monophyly of the genusPopulusis strongly supported by nuclear and plastid gene, which is consistent with previous studies.P. mexicana, diverged first in the nuclear DNA tree, which occupied the basal position, implying that the section Abaso may be the most ancestral lineage in extant populous species. Given that the short branches and low statistical support for the divergence of sections Abaso and Turanga, this observation probably indicated that a rapid radiation evolution following the early split of the genusPopulus. In the plastid tree,P. mexicanaclustered with modern-day species of section Tacamahaca in the plastid tree. Based on cytoplasmic and single-copy nuclear marker sequences, we hypothesized that chloroplast capture resulted in the inconsistent position ofP. mexicanabetween the phylogenetic trees. Given the first unequivocal records of poplar fossils from the Eocene with similar leaf morphology to the extantP. mexicanaand the phylogenetic positions ofP. mexicanain our study, we support the hypothesis that thePopulusgenus originated in North America, which will provide new insights to the development of the origin ofPopulusspecies.
authors.affiliation: State Key Laboratory of Tree Genetics and Breeding, Key Laboratory of Silviculture of the State Forestry Administration, Research Institute of Forestry, Chinese Academy of Forestry Beijing, China.
authors.forename: Xia
authors.initials: X
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Tree Genetics and Breeding, Key Laboratory of Silviculture of the State Forestry Administration, Research Institute of Forestry, Chinese Academy of ForestryBeijing, China; Collaborative Innovation Center of Sustainable Forestry in Southern China, Nanjing Forestry UniversityNanjing, China.
authors.forename: Zhaoshan
authors.initials: Z
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Tree Genetics and Breeding, Key Laboratory of Silviculture of the State Forestry Administration, Research Institute of Forestry, Chinese Academy of ForestryBeijing, China; Research Institute of Subtropical Forestry, Chinese academy of ForestryHangzhou, China.
authors.forename: Wenhao
authors.initials: W
authors.lastname: Shao
authors.affiliation: State Key Laboratory of Tree Genetics and Breeding, Key Laboratory of Silviculture of the State Forestry Administration, Research Institute of Forestry, Chinese Academy of Forestry Beijing, China.
authors.forename: Zhanyang
authors.initials: Z
authors.lastname: Ye
authors.affiliation: State Key Laboratory of Tree Genetics and Breeding, Key Laboratory of Silviculture of the State Forestry Administration, Research Institute of Forestry, Chinese Academy of ForestryBeijing, China; Collaborative Innovation Center of Sustainable Forestry in Southern China, Nanjing Forestry UniversityNanjing, China.
authors.forename: Jianguo
authors.initials: J
authors.lastname: Zhang
keywords: Populus mexicana; chloroplast DNA; phylogenetic; plant evolution; single-copy nuclear; taxonomic status