Genetic and phenotypic variation among Turkish terrestrial orchid species as revealed by RAPD and morphological characteristics


Abstract: Terrestrial orchid species are natural sources of salep and a closely related group of plant species widely distributed throughout Turkey. The phylogenetic relationship among fourteen different tuber-producing orchid species was investigated after analyzing phenotypic and genetic variation within and among the natural population through fifteen morphometric traits and ten random amplified polymorphic DNA (RAPD) primer combinations. Statistical analyses (principal component analysis (PCA), principal coordinate analysis (PCoA), and cluster analysis) using the generated data identified taxonomic and genetic distance within the studied plant samples. The results of PCA from morphological traits show that there are no major groupings within and among different species instead somehow overlapping with few distinctly characterized species. In addition, the UPGMA-based phenogram with Euclidean distance (0-1) produces five major clusters among the studied orchid species according to their taxonomic status with few exceptions. On the other hand, PCoA and the phylogenetic dendrogram with the coefficient (0.56-0.79) from RAPD band profiles determine the true genetic diversity of those species. Although both combinations of genetic and phenotypic characteristics reveal the phylogenetic relationship of some those studied species very effectively, they are not clear for others. These results suggest that in the natural population of terrestrial orchid species significant amounts of gene flow are ongoing at intra/interspecies level. Therefore, it is recommended that conservation studies of these groups of orchid species should be done as a geographical unit rather than according to taxonomic status.

Keywords: Characterization, terrestrial orchids, Turkey, principal component analysis, principal coordinate analysis, random amplified polymorphic DNA

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