Integrative Phylogenetic Study of Bulbophyllum Species (Orchidaceae), Based on Morphological Characters, nrITS and...

Bulbophyllum is a large and highly diverse genus of the family Orchidaceae. Investigations in the Northeast Indian region have revealed an abundance of various Bulbophyllum species. However, the taxonomy and phylogeny of these North-eastern species still remain unresolved. This study is the first comprehensive phylogenetic assessment of 20 species of Bulbophyllum from Northeast India, revealing new insights into their relationships. The complete nuclear ITS region (nrITS) (ITS1, 5.8S, ITS2) and the non-coding psbA-trnH intergenic spacer of plastid DNA, together with the morphometric characters were used to resolve the phylogeny of Bulbophyllum species of Northeast India. Individual as well as combined datasets were analysed to evaluate marker performance and overall resolution. The nrITS dataset showed better resolving ability as compared to plastid DNA marker. Phylogenetic trees generated from the combined analysis of morphological and molecular dataset provided the most robust phylogenetic framework, particularly at the sectional level. The results support the inclusion of B. reptans in the section Reptantia, rather than in Racemosae. The three species viz. B. odoratissimum, B. trichocephalum and B. cauliflorum were found to have a closer relationship suggesting that they belong to the same section. The section Desmosanthes needs further investigation to re-define its boundaries. Overall, this integrative approach improves the resolution of phylogenetic relationships within Bulbophyllum and provides a refined taxonomic framework. Furthermore, taxonomic key for the 20 species has also been developed to facilitate accurate identification, based on reliable diagnostic traits.