Abstract: Objective: To explore and infer the phylogenetic position of the brown seaweed Turbinaria ornata based on the rbcl gene. Methods: The brown seaweed, T. ornata was collected from Nalupanai coast of Gulf of Mannar. DNA extraction was performed by Cetyl-Trimethyl-Ammonium-Bromide (CTAB) method. DNA fragments coding for rbcl gene were amplified from total genomic DNA with oligonucleotide primers (Paul et al., 2000). Automated sequencing was performed on an ABI Prism 310 Genetic Analyzer (Applied Biosystems). A minimum of two strands were sequenced in both directions. Analysis was done using the protocol BDTv3-KB-Denovo version 5.2. Results: The phylogenetic analysis of Turbinaria ornata shows its evolutionary relationship to the common ancestor Sargassaceae. The evolutionary trees reveal monophyletic origin of Turbinaria along with Sargassum. The trees constructed by different methods such as Neighbor Joining, Maximum Likelihood and Maximum Parsimony and their bootstrap values also support that the Turbinaria species is closely related to Sargassum and the origin of T. ornata is recent. Conclusion: The molecular data proves that this Turbinaria species is related to Sargassaceae members and shares common ancestry.

Keywords: Turbinaria ornata, phylogeny, rubisco gene, rbcl.