A survey along the east coast of Thailand reveals high diversity in the genus Lobophora (Dictyotales, Phaeophyceae): with the description of four new species

Lobophora (Dictyotales, Phaeophyceae) is an ecologically important seaweed genus in tropical and subtropical marine ecosystems. This alga exhibits cryptic diversity and morphological plasticity, which require taxonomic delineations that primarily depend on DNA analyses, complemented by morphological and ecological data. Species diversity and distribution within Southeast Asia remain understudied compared to well-documented regions such as the Caribbean and the western Pacific. This study provides a comprehensive assessment of the genus Lobophora along the east coast of Thailand, integrating DNA-based surveys with morphological analyses. Extensive sampling across the Gulf of Thailand revealed 14 well-supported monophyletic clades of Lobophora. Among these, we described four new species (L. lewmanomontiae sp. nov., L. ogawae sp. nov., L. thiemmedhii sp. nov., and L. velasquezii sp. nov.) and reported three new national records (L. abscondita, L. henae, and L. quangtriensis), thereby bringing the Thai total to 21 species. When combined with previous records, 30 species have now been recorded from Southeast Asia, with 12 of which are endemic to the region. This study also emphasizes the importance of extensive sampling across broader areas, which enhances our understanding of biogeographic distributions and their implications for coastal ecosystem management.