Thomas’ lidflower (Calyptranthes thomasiana) is a small, evergreen shrub or small tree which grows on just three islands in the Caribbean (1)(2)(4)(5). Its leathery, oval leaves grow in opposite pairs and measure between 2 and 6.5 centimetres long and up to 3 centimetres across (2)(3). The leaves are shiny on the upper surface and dull on the lower surface, and are fairly rounded at the tip (2)(3).
The flower buds of Thomas’ lidflower are egg-shaped, with a pointed tip. The flowers of this species have four small, spatula-shaped petals and grow in clusters, or inflorescences, with each flower forming at the tip of a growing stem and further flowers developing on branches below it (2). The fruit of Thomas’ lidflower has not been described, but like other Calyptranthes species it is likely to contain one or two seeds (6).
Very little is currently known about the biology of Thomas’ lidflower (2). It has been seen flowering and fruiting regularly on Virgin Gorda and has been reported to have high seed production and germination on St John (1)(2). Bats have been seen feeding on the fruits, and may be important in dispersing the plant’s seeds (1).
Although originally described from the island of St Thomas, one of the US Virgin Islands (2)(4), Thomas’ lidflower has not been recorded on the island in recent years and is now only likely to occur there in cultivation (1)(2)(5).
Thomas’ lidflower is now known from just three other locations: at Monte Pirata on Vieques Island, Puerto Rico; from Bordeaux Mountain on St John, in the US Virgin Islands; and from Gorda Peak on Virgin Gorda, one of the British Virgin Islands (1)(2)(4)(5).
The loss of this species from St Thomas is likely to have been due to development on the island (1)(5). The remaining populations of Thomas’ lidflower are small and fragmented, occupying a total area of less than 294 square kilometres (1), and are under continued threat from habitat loss and feral animals, which uproot seedlings (1)(2)(4). With such a small and restricted population, Thomas’ lidflower is also vulnerable to any extreme events, such as hurricanes (2)(4).
On Vieques Island, only 10 to 12 mature Thomas’ lidflowers remain (1)(2). These occur in a conservation zone owned by the U.S. Navy, but any expansion of the Navy facilities could threaten this species (1)(2)(4). On St John, Thomas’ lidflower is found inside a National Park (1)(4), but feral donkeys, goats and pigs still pose a threat (2)(4), and only around 100 mature individuals are left on the island (1)(2). Approximately 59 Thomas’ lidflowers are thought to occur on Virgin Gorda (1), which is fewer than previously estimated (2)(5). These individuals occur in two subpopulations, and although both are located within a National Park, one is close to an area where development is taking place. Loose cattle in the park may also pose a threat (1).
As the global population of Thomas’ lidflower is now believed to be below 250, it may soon qualify for listing as Critically Endangered on the IUCN Red List (1).
Thomas’ lidflower is listed as Endangered on the U.S. Federal Endangered Species Act (7) and a recovery plan has been developed for the species, mainly covering the Vieques Island and St John populations (2). The main aims of the recovery plan are to protect and monitor the existing populations of Thomas’ lidflower, to develop a management plan, to perform further research into its life history, and to attempt to establish new populations (2). An accurate and up-to-date census of the wild Thomas’ lidflower population is also needed to clarify its current conservation status (1).
The U.S. Navy and the U.S. National Park Service are aware of the presence of Thomas’ lidflower on their land on Vieques, and any proposed developments there must be approved (2). On St John, Thomas’ lidflower occurs within the Virgin Islands National Park (1)(2), where management practices are being put in place to prevent feral animals from uprooting and trampling the plants (1).
On Virgin Gorda, Thomas’ lidflower occurs within the Gorda Peak National Park, and the two subpopulations are being regularly monitored. A management plan has been developed for the park, and a control programme is starting to address the problem of free-roaming cattle (1). The BVI National Parks Trust is attempting to establish Thomas’ lidflower in cultivation (1), and it is also being grown at the Fairchild Tropical Gardens in Miami, Florida (2)(4).
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