Researchers have a population of an extremely rare plant species, last recorded in Sri Lanka in 1855, growing in a lowland forest fragment along the Sitawaka Ganga River.
Documenting the finding in a recent study, researchers write that the plant, Indianthus virgatus, while officially listed as critically endangered in Sri Lanka, was presumed possibly extinct in the wild in the country.
I. virgatus, which has small white flowers, grows in the understory of wet tropical forests. It’s known from some 150 locations in India, but the only verified record of the plant in Sri Lanka is from a specimen collected in 1855, the study says.
Using a combination of historical records across India and Sri Lanka, and predictive habitat modeling to identify potential habitats, researchers looked for the plant in southwestern Sri Lanka, in Sabaragamuwa Province.
In January 2025, the research team successfully located a small population of I. virgatus of 70 to 100 individuals. This population was found in an area that researchers had predicted to be highly suitable for the species.
I. virgatus, which is the only species within the Indianthus genus, has unique evolutionary and biogeographical context, said Vivek Pandi, coauthor of the study and assistant professor of ecology and evolutionary biology at Manipal Academy of Higher Education, India.
The species has a disjunct occurrence across the Indian subcontinent and Sri Lanka, Pandi told Mongabay by email, meaning populations of the species are separated by a large geographical gap. This raises an intriguing question, he added, about whether an ancient geological event split the once-continuous population of the plant into two separate groups; or whether the species reached Sri Lanka later through long-distance dispersal.
Though I. virgatus went unrecorded in the wild in Sri Lanka for 170 years, Pandi said the researchers think the species survived undetected in sheltered pockets of forest over the decades.
According to Pandi, these areas include small remnants of moist, shaded forest — typically around streams and sheltered slopes — that can retain stable microclimatic conditions despite severe disturbance in the surrounding landscape.
“The rediscovery of I. virgatus highlights why these seemingly small and isolated forest remnants can be important for conserving poorly known species,” Pandi said.
Protecting these micro-refugia is urgent, as most of the plant’s suitable habitats in Sri Lanka have been destroyed by tea and rubber plantations, the study notes. Populations of the plant in the Western Ghats also face habitat-related threats, Pandi said.
Effectively safeguarding the newly found population in Sri Lanka will require a combination of immediate local habitat protection and efforts to establish collections of the plant at national botanical gardens, the study’s authors write.
They add that the conservation status of I. virgatus also needs to be assessed for the IUCN Red List, so its protection can be integrated into national and regional biodiversity action plans.
Banner image of Indianthus virgatus growing along the shaded bank of a stream in lowland forest. Image courtesy of Vishnu et al., 2026 (CC BY-NC 4.0).
