Three new Lobophora species (Dictyotales, Phaeophyceae) from Phuket on the west coast of Thailand

The systematics and biogeography of the brown seaweed genus Lobophora (Dictyotales) are increasingly being investigated globally using DNA data coupled with morphology. In Thailand, DNA-assisted Lobophora diversity assessment has been limited to the east coast. The present study employed molecular (cox3, psbA, and rbcL gene sequences) and morphological analyses to explore the diversity of Lobophora around Phuket Island on the Thai west coast. Our findings revealed three new species: Lobophora phuketensis sp. nov., L. andamanensis sp. nov., and L. rachaensis sp. nov. Phylogenetic analyses clearly demonstrated that these new species are genetically distinct from other Lobophora species. These new Lobophora species can be distinguished morphologically by differences in their growth habit, coloration, and thallus thickness, despite some overlapping morphological traits. Our study has increased the known Lobophora diversity in Thailand to 12 species, the highest in Southeast Asia. We also detected ecological similarities and differences among these Lobophora species. This research enhances our understanding of the biodiversity and biogeographic patterns of Lobophora in Thailand and the Central Indo-Pacific region. Further studies should investigate Lobophora diversity in unsampled areas and explore ecological factors facilitating sympatric coexistence through field observations and experiments.