A New Distribution Record of Acrotrema dissectum Thwaites (Dilleniaceae); A Critically Endangered Endemic Plant Species in Sri Lanka

Abstract

Acrotrema dissectum Thwaites (Dilleniaceae) is a Critically Endangered (CE) endemic plant from Sri Lanka according to the National Red List, 2020 which last recorded in 1969. We aimed to rediscover A. dissectum from selected habitats in Sri Lanka to enrich the National Herbarium collection for the future Red List assessment and to develop ex-situ conservation protocols. Explorations were conducted for selected forest areas based on herbarium data, botanical literature and personal communications in the Kaluthara district in November 2022. We recovered about 15-20 individuals at a previously undocumented location. The population was restricted to a moss-covered, steep rock surface adjacent to a stream in a small, disturbed forest patch. Specimens were photographically documented and identified using existing records in the National Herbarium collection, historical botanical illustrations and literature. Photograph vouchers were deposited at the National Herbarium, Peradeniya. The original location where the species was described, Hewesse (1855) “Hellesse, Pasdun Korle”, Gualanawatta forest (1969) and the newly discovered locality fall within the same geographical area, suggesting the species has a restricted distribution. Ecological niche modelling based on these localities may help identify additional populations. Attempts to establish individuals in National Botanic Garden nurseries were unsuccessful, indicating that propagation methods require optimization before effective ex-situ conservation can be implemented. This rediscovery provides crucial baseline data for conservation planning and highlights the need for habitat protection and further population surveys in the Kalutara region.

Keywords: New record, Acrotrema dissectum, Critically endangered, Endemic species, Conservation