Range extension and conservation status of the rare Solanaceae shrub, Solanum conocarpum

Abstract

The British Virgin Islands and the US Virgin Islands, two island groups located in the Caribbean archipelago, hold unique plant diversity and high endemism. Until recently, Solanum conocarpum was considered a rare plant species endemic to the island of St. John in the US Virgin Islands. Ongoing botanical surveys in this region are revealing new populations and refining our understanding of the distribution of these narrow endemic plant species. The objective of this paper is to assess the conservation status of S. conocarpum, including a review of its geographic range, population numbers, threats and conservation actions needed for its long-term survival. In this paper, we present new occurrences for S. conocarpum, extending its geographic range to a new island, Tortola and new territory, the British Virgin Islands. Despite this range expansion, this species is evaluated as Endangered (EN), based on Criteria B1b(iii,v)+2b(iii,v)+C2a(i), according to the IUCN Red List Categories and Criteria. The extent of occurrence (EOO = 46 km2) and area of occupancy (AOO = 20 km2) are highly restricted. On St. John (US Virgin Islands), the historically recorded individuals at Reef Bay, Europa Ridge and Sabbat Point are now considered extirpated due to disturbance from development compounded by invasive species, as well as the impact of feral ungulates and drought stress. These threats are impacting the species across the whole island of St. John and contributing to a continuing decline of suitable habitat, despite the island being a National Park. On the island of Tortola, the species occurs on unprotected lands subject to development and habitat modification and decline by feral ungulates. Based on these threats acting separately across the two islands, two locations were defined. The estimated total number of mature individuals ranges between 150 and 250, with the largest subpopulation at Nanny Point in the US Virgin Islands, containing 108 mature individuals. Conservation action, focused on protecting this species' habitat, is urgently needed.