title: Age estimation for the genus Cymbidium (Orchidaceae: Epidendroideae) with implementation of fossil data calibration using molecular markers (ITS2 & matK) and phylogeographic inference from ancestral area reconstruction.
abstract: Intercontinental dislocations between tropical regions harboring two-thirds of the flowering plants have always drawn attention from taxonomists and biogeographers. One such family belonging to angiosperms is Orchidaceae with an herbaceous habit and high species diversity in the tropics. Here, we investigate the evolutionary and biogeographical history of the genus Cymbidium, which represents a monophyletic subfamily (Epidendroideae) of the orchids and comprises 50 odd species that are distinctly distributed in tropical to temperate regions. Much is not known about correlations among the level of CAM activity (one of the photosynthetic pathways often regarded as an adaptation to water stress in land plants), habitat, life forms, and phylogenetic relationships of orchids from an evolutionary perspective. A relatively well-resolved and highly supported phylogeny for Cymbidium orchids is reconstructed based on sequence analysis of ITS2 and matK regions from the chloroplast DNA available in public repositories viz. GenBank at NCBI. This study examines a genus level analysis by integrating different molecular matrices to existing fossil data on orchids in a molecular Bayesian relaxed clock employed in BEAST and assessed divergence times for the genus Cymbidium with a focus on evolutionary history of photosynthetic characters. Our study has enabled age estimations (45Ma) as well as ancestral area reconstruction for the genus Cymbidium using BEAST by addition of previously analyzed two internal calibration points.
authors.affiliation: * Bioinformatics Centre, North-Eastern Hill University, Shillong, Meghalaya, India.
authors.forename: Ruchishree
authors.initials: R
authors.lastname: Konhar
authors.affiliation: * Bioinformatics Centre, North-Eastern Hill University, Shillong, Meghalaya, India.
authors.forename: Manish
authors.initials: M
authors.lastname: Debnath
authors.affiliation: † Department of Botany, North-Eastern Hill University, Shillong, Meghalaya, India.
authors.forename: Jean Valrie
authors.initials: JV
authors.lastname: Marbaniang
authors.affiliation: * Bioinformatics Centre, North-Eastern Hill University, Shillong, Meghalaya, India.
authors.forename: Devendra Kumar
authors.initials: DK
authors.lastname: Biswal
authors.affiliation: ‡ Biotech Park, Lucknow, Uttar Pradesh, India.
authors.forename: Pramod
authors.initials: P
authors.lastname: Tandon
mesh_terms: D001499:Bayes Theorem; D002138:Calibration; D021903:DNA, Ribosomal Spacer / Q000235:genetics; D004722:Endoribonucleases / Q000235:genetics; D005580:Fossils; D005819:Genetic Markers; D008954:Models, Biological; D009713:Nucleotidyltransferases / Q000235:genetics; D029595:Orchidaceae / Q000235:genetics / Q000502:physiology*; D010802:Phylogeny; D058974:Phylogeography; D013997:Time Factors
chemical_list: D021903:DNA, Ribosomal Spacer; D005819:Genetic Markers; D009713:Nucleotidyltransferases; C034038:mRNA maturase; D004722:Endoribonucleases
keywords: Ancestral area reconstruction; Bayesian relaxed clock; Cymbidium; fossil; internal transcribed spacers; maturase K