title: Genome origin, historical hybridization and genetic differentiation in Anthosachne australasica (Triticeae; Poaceae), inferred from chloroplast rbcL, trnH-psbA and nuclear Acc1 gene sequences.
abstract: Anthosachne Steudel is a group of allopolyploid species that was derived from hexaploidization between the Asian StY genome Roegneria entity and the Australasia W genome Australopyrum species. Polyploidization and apomixis contribute to taxonomic complexity in Anthosachne Here, a study is presented on the phylogeny and evolutionary history of Anthosachne australasica The aims are to demonstrate the process of polyploidization events and to explore the differentiation patterns of the St genome following geographic isolation.
  
  
  
  Chloroplast rbcL and trnH-psbA and nuclear Acc1 gene sequences of 60 Anthosachne taxa and nine Roegneria species were analysed with those of 33 diploid taxa representing 20 basic genomes in Triticeae. The phylogenetic relationships were reconstructed. A time-calibrated phylogeny was generated to estimate the evolutionary history of A. australasica Nucleotide diversity patterns were used to assess the divergence within A. australasica and between Anthosachne and its putative progenitors.
  
  
  
  Three homoeologous copies of the Acc1 sequences from Anthosachne were grouped with the Acc1 sequences from Roegneria, Pseudoroegneria, Australopyrum, Dasypyrum and Peridictyon The chloroplast sequences of Anthosachne were clustered with those from Roegneria and Pseudoroegneria Divergence time for Anthosachne was dated to 4·66 million years ago (MYA). The level of nucleotide diversity in Australasian Anthosachne was higher than that in continental Roegneria A low level of genetic differentiation within the A. australasica complex was found.
  
  
  
  Anthosachne originated from historical hybridization between Australopyrum species and a Roegneria entity colonized from Asia to Australasia via South-east Asia during the late Miocene. The St lineage served as the maternal donor during the speciation of Anthosachne A contrasting pattern of population genetic structure exists in the A. australasica complex. Greater diversity in island Anthosachne compared with continental Roegneria might be associated with mutation, polyploidization, apomixis and expansion. It is reasonable to consider that A. australasica var. scabra and A. australasica var. plurinervisa should be included in the A. australasica complex.
authors.affiliation: Triticeae Research Institute, Sichuan Agricultural University, Wenjiang 611130, Sichuan, China.|Key Laboratory of Crop Genetic Resources and Improvement, Ministry of Education, Sichuan Agricultural University, Yaan 625014, Sichuan, China.
authors.forename: Li-Na
authors.initials: LN
authors.lastname: Sha
authors.affiliation: Triticeae Research Institute, Sichuan Agricultural University, Wenjiang 611130, Sichuan, China.
authors.forename: Xing
authors.initials: X
authors.lastname: Fan
authors.affiliation: College of Life Sciences, Sichuan Agricultural University, Yaan 625014, Sichuan, China.
authors.forename: Xiao-Li
authors.initials: XL
authors.lastname: Wang
authors.affiliation: Triticeae Research Institute, Sichuan Agricultural University, Wenjiang 611130, Sichuan, China.
authors.forename: Zhen-Zhen
authors.initials: ZZ
authors.lastname: Dong
authors.affiliation: College of Resources, Sichuan Agricultural University, Wenjiang 611130, Sichuan, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Zeng
authors.affiliation: Triticeae Research Institute, Sichuan Agricultural University, Wenjiang 611130, Sichuan, China.
authors.forename: Hai-Qin
authors.initials: HQ
authors.lastname: Zhang
authors.affiliation: Triticeae Research Institute, Sichuan Agricultural University, Wenjiang 611130, Sichuan, China.
authors.forename: Hou-Yang
authors.initials: HY
authors.lastname: Kang
authors.affiliation: Triticeae Research Institute, Sichuan Agricultural University, Wenjiang 611130, Sichuan, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Wang
authors.affiliation: College of Life Sciences, Sichuan Agricultural University, Yaan 625014, Sichuan, China.
authors.forename: Jin-Qiu
authors.initials: JQ
authors.lastname: Liao
authors.affiliation: Triticeae Research Institute, Sichuan Agricultural University, Wenjiang 611130, Sichuan, China zhouyh@sicau.edu.cn.|Key Laboratory of Crop Genetic Resources and Improvement, Ministry of Education, Sichuan Agricultural University, Yaan 625014, Sichuan, China.
authors.forename: Yong-Hong
authors.initials: YH
authors.lastname: Zhou
mesh_terms: D001483:Base Sequence; D018742:DNA, Chloroplast / Q000235:genetics / Q000302:isolation & purification; D018744:DNA, Plant / Q000235:genetics / Q000302:isolation & purification; D017343:Genes, Plant / Q000235:genetics; D014644:Genetic Variation / Q000235:genetics; D018745:Genome, Plant / Q000235:genetics*; D010802:Phylogeny; D000069600:Plant Breeding; D006109:Poaceae / Q000235:genetics*; D017422:Sequence Analysis, DNA
chemical_list: D018742:DNA, Chloroplast; D018744:DNA, Plant
keywords: Anthosachne; Phylogeny; apomixis; genetic differentiation; genome origin