The genus Hypnea (Rhodophyta: Cystocloniaceae) in the reef platform of Providencia and Santa Catalina islands, Seaflower Biosphere Reserve, Caribbean Colombia: taxonomy and distribution

Abstract

The red algal genus Hypnea (Cystocloniaceae) is taxonomically challenging due to its high morphological plasticity and cryptic diversity. This study aimed to characterize Hypnea species occurring on the reef platform of Providencia and Santa Catalina islands (southwestern Caribbean) and to assess their spatial distribution and benthic cover. Species identification was conducted using an integrative approach combining morphological analyses with DNA sequence data from the cytochrome c oxidase subunit I marker (COI-5P) and the plastid ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit gene ( rbc L), while benthic cover was quantified using transects and quadrats. Three species were confirmed: Hypnea caraibica , Hypnea cryptica , and Hypnea spiniformis , together with one unresolved lineage within the “ musciformis ” complex. Hypnea was recorded at 12 sites in 2023 and 16 in 2024, and the mean benthic cover of the genus increased from 1.97 % to 3.97 %. The species exhibited distinct habitat associations across the reef platform. This study provides the first molecularly supported assessment of Hypnea diversity in the Archipelago and highlights the importance of integrative taxonomy for resolving macroalgal diversity in coral reef ecosystems.