Biogeography of the Phalaenopsis amabilis species complex inferred from nuclear and plastid DNAs.
Phalaenopsis is one of the important commercial orchids in the world. Members of the P. amabilis species complex represent invaluable germplasm for the breeding program. However, the phylogeny of the P. amabilis species complex is still uncertain. The Phalaenopsis amabilis species complex (Orchidaceae) consists of subspecies amabilis, moluccana, and rosenstromii of P. amabilis, as well as P. aphrodite ssp. aphrodite, P. ap. ssp. formosana, and P. sanderiana. The aims of this study were to reconstruct the phylogeny and biogeographcial patterns of the species complex using Neighbor Joining (NJ), Maxinum Parsimony (MP), Bayesian Evolutionary Analysis Sampling Trees (BEAST) and Reconstruct Ancestral State in Phylogenies (RASP) analyses based on sequences of internal transcribed spacers 1 and 2 from the nuclear ribosomal DNA and the trnH-psbA spacer from the plastid DNA.



A pattern of vicariance, dispersal, and vicariance + dispersal among disjunctly distributed taxa was uncovered based on RASP analysis. Although two subspecies of P. aphrodite could not be differentiated from each other in dispersal state, they were distinct from P. amabilis and P. sanderiana. Within P. amabilis, three subspecies were separated phylogenetically, in agreement with the vicariance or vicariance + dispersal scenario, with geographic subdivision along Huxley's, Wallace's and Lydekker's Lines. Molecular dating revealed such subdivisions among taxa of P. amabilis complex dating back to the late Pleistocene. Population-dynamic analyses using a Bayesian skyline plot suggested that the species complex experienced an in situ range expansion and population concentration during the late Last Glacial Maximum (LGM).



Taxa of the P. amabilis complex with disjunct distributions were differentiated due to vicariance or vicariance + dispersal, with events likely occurring in the late Pleistocene. Demographic growth associated with the climatic oscillations in the Würm glacial period followed the species splits. Nevertheless, a subsequent population slowdown occurred in the late LGM due to extinction of regional populations. The reduction of suitable habitats resulted in geographic fragmenttation of the remaining taxa.
Crop Improvement Division, Kaohsiung District Agricultural Improvement Station, Pingtung, 900, Taiwan. tsaicc@mail.kdais.gov.tw.|Graduate Institute of Biotechnology, National Pingtung University of Science and Technology, Pingtung, 912, Taiwan. tsaicc@mail.kdais.gov.tw.
Chi-Chu
CC
Tsai
Department of Biological Sciences, National Sun Yat-sen University, Kaohsiung, 804, Taiwan. choumasa@mail.cmu.edu.tw.|Research Center for Biodiversity, China Medical University, Taichung, 404, Taiwan. choumasa@mail.cmu.edu.tw.
Chang-Hung
CH
Chou
Department of Life Science, National Cheng Kung University, Tainan, 701, Taiwan. hvwang@mail.ncku.edu.tw.
Hao-Ven
HV
Wang
Department of Biological Sciences, National Sun Yat-sen University, Kaohsiung, 804, Taiwan. abscl77512@yahoo.com.tw.
Ya-Zhu
YZ
Ko
Department of Life Science, National Cheng Kung University, Tainan, 701, Taiwan. tychiang@mail.ncku.edu.tw.
Tzen-Yuh
TY
Chiang
Department of Biological Sciences, National Sun Yat-sen University, Kaohsiung, 804, Taiwan. yuchung@mail.nsysu.edu.tw.|Department of Biomedical Science and Environment Biology, Kaohsiung Medical University, Kaohsiung, 807, Taiwan. yuchung@mail.nsysu.edu.tw.
Yu-Chung
YC
Chiang
D001499:Bayes Theorem; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism; D018742:DNA, Chloroplast / Q000235:genetics / Q000378:metabolism; D018744:DNA, Plant / Q000235:genetics* / Q000378:metabolism; D004275:DNA, Ribosomal / Q000235:genetics* / Q000378:metabolism; D021903:DNA, Ribosomal Spacer / Q000235:genetics / Q000378:metabolism; D051456:Gene Flow; D008969:Molecular Sequence Data; D029595:Orchidaceae / Q000166:cytology / Q000235:genetics / Q000502:physiology*; D010802:Phylogeny; D058974:Phylogeography; D063148:Plant Dispersal; D017422:Sequence Analysis, DNA
D018742:DNA, Chloroplast; D018744:DNA, Plant; D004275:DNA, Ribosomal; D021903:DNA, Ribosomal Spacer