Two flowering plants, one from the Nicobar Islands and the other from the Andamans, have been recorded from the Andaman and Nicobar Archipelago for the first time, expanding the known plant diversity of the islands.
The study has also resolved the identity of a plant earlier considered endemic to the archipelago and excluded another species from its flora after researchers found no verifiable evidence of its occurrence.
The findings are part of a study titled “Taxonomic Notes and New Records of Lythraceae from the Andaman and Nicobar Archipelago, India”, authored by researchers including Arikrishnan Parthiban, Ladan Rasingam, Sagarika Kumari and Lal Ji Singh.
Researchers recorded Cuphea carthagenensis from Great Nicobar Island, marking the first confirmed natural occurrence of the genus Cuphea in the Andaman and Nicobar Islands. A small annual herb growing up to around 50 cm, C. carthagenensis has erect, branched stems and small opposite leaves. Its tiny flowers occur singly in the leaf axils. Native to tropical America, the species has become naturalised in several parts of the world and is commonly found in disturbed habitats, including cultivated fields, bare ground and roadside ditches. The species was first traced in the islands through a herbarium specimen collected from Campbell Bay in 2011 and identified at the time as Ammannia baccifera. Its occurrence was confirmed after another specimen was collected from Magar Nallah in Campbell Bay in April 2026.
The second new record, Rotala rosea, was collected from Lamiya Bay in the North Andamans in June 2025. It is a small amphibious annual herb found in or around waterlogged habitats and paddy fields. Its stems can grow up to about 45 cm and may creep along the ground before producing erect branches. The plant bears small sessile flowers with translucent to pink petals and a green, rounded ovary. It is native to tropical and subtropical Asia and extends to northern Australia.
The researchers also revisited the taxonomic status of Rotala andamanensis, which had been considered endemic to the islands. Examination of type specimens showed that its characteristics correspond to Rotala indica. The study therefore treats R. andamanensis as a synonym of R. indica, in line with an earlier taxonomic treatment.
At the same time, the study has excluded Rotala illecebroides from the flora of the Andaman and Nicobar Islands. The species was reported from the archipelago in a 2023 flora, but researchers could not trace any authentic specimens supporting its occurrence. Several specimens identified as R. illecebroides were found to be R. indica instead.
Earlier revisionary studies have recorded R. illecebroides as endemic to peninsular India.
The findings are based on detailed examination of plant morphology, field observations and comparisons with type specimens and other herbarium collections.