Decline in Occurrence and Distribution of Sesamum prostratum, a Crop Wild Relative of Sesame, along the Eastern Coastal Region of India

An exploration was undertaken for collection of the narrow-endemic wild relative of sesame, Sesamum prostratum Retz., a potential Critically Endangered (CR) species, specific to the coastal habitats, in the strands between 150-300 m from the sea shore of the east coast. Herbarium specimens, the authentic source for occurrence and distribution, for S. prostratum at various herbaria (collected during 1802-1988) are available. A trip was undertaken in Dec. 2020 along the east coast region of Tamil Nadu, between the latitudes 10.29 N to 13.56 N, that covered all previously recorded collection sites. Unfortunately, in 71% of the sites surveyed, S. prostratum was absent. All the sites with S. prostratum were found to be undisturbed or with minimal human interference. Our preliminary assessment as per the IUCN guidelines suggests for CR category. In sites around the Chennai sea shore, we found Canavalia rosea, with Ipomoea pes-caprae, while the endemic S. prostratum was absent. The loss could be due to two reasons, habitat-based-probable spread of introduced species such as Ipomoea pescaprae, protection afforded to Spinifex littoreus (besides severe urbanization, cyclonic storms, and tsunami, where the habitat itself is fragmented and prone to disasters) and the non-competitive nature of the species. Strategies for threat assessment (especially post-disasters) with an action plan, is discussed that could prevent extinction risk, especially of endemic.