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Biswal DK, Marbaniang JV, Tandon P.2013. Age estimation for Asian Cymbidium (Orchidaceae: Epidendroideae) with implementation of fossil data calibration using molecular markers (ITS2 & matK) implying phylogeographic inference. PeerJ PrePrints1:e94v1https://doi.org/10.7287/peerj.preprints.94v1
Abstract: Intercontinental dislocations between tropical regions harboring two-thirds of the flowering plants have always drawn attention from taxonomists and bio-geographers. The focus had always been on woody land plants rather than on herbs. Orchidaceae is one such family belonging to angiosperms, with an herbaceous habit and high species diversity in the tropics. Here, we investigate the evolutionary and bio-geographical history of the genus Cymbidium, which represents a monophyletic subfamily (Epidendroideae) of the orchids and comprises 50 odd species that are disjunctly distributed in tropical to temperate regions. A relatively well-resolved and highly supported phylogeny of Cymbidiums was reconstructed based on sequence analyses of internal transcribed spacer (ITS2) regions and maturaseK (matK) from the chloroplast region available on the public domain in GenBank at NCBI. Crassulacean acid metabolism (CAM) is one of the photosynthetic pathways regarded as adaptation to water stress in land plants. Hardly any information exists on correlations among the level of CAM activity, habitat, life form, and phylogenetic relationship of a plant group from an evolutionary perspective. This study examines a genus level analyses by integrating ITS and matK data to all fossil data available on orchids in a molecular Bayesian relaxed clock employed in BEAST and assessed divergence times for the genus Cymbidium with a focus on evolutionary plasticity of photosynthetic characters. Our study has enabled age estimations for the genus Cymbidum (12Ma) for the first time using BEAST by addition of previously analyzed two internal calibration points.
This paper was submitted to the InCoB 2013 Conference (International Conference on Bioinformatics). It was accepted for presentation at the Conference and is also being submitted to PeerJ.