Agrostis trachychlaena (bentgrass)
A rare grass species, Agrostis trachychlaena occurs within an area of only 16 km² on two islands in the South Atlantic Ocean. Fewer than 250 mature individuals are thought to survive.
Agrostis trachychlaena (Photo: Niek Gremmen)
Agrostis trachychlaena C.E. Hubb.
bentgrass (although this name is also applied to other species within this genus)
Endangered (EN) according to IUCN Red List criteria.
Rocky slopes, open patches in Spartina arundinacea tussock, and around albatross nesting sites.
About this species
Agrostis trachychlaena is a rare species of grass that grows in loose clumps on rocky slopes on two islands in the South Atlantic Ocean. Specimens of A. trachychlaena were first brought back from Inaccessible and Nightingale Islands by botanist Erling Christophersen, as part of the Norwegian Scientific Expedition in 1938. Specimens from Nightingale Island were collected by scientist Nigel M. Wace on his visits in 1968 and 1976. The most recent collections were made by Peter Ryan in 2007.
Geography and distribution
Agrostis trachychlaena is restricted to Inaccessible Island and Nightingale Island in the South Atlantic Ocean. These islands are part of the Tristan da Cunha group, which is located 2,400 km south of St Helena (the UK Overseas Territory of which Tristan da Cunha is a dependency).
Overview: A short, perennial herb growing in loose clumps, with culms (stems) of 20-55 cm long.
Leaves: The ligule (appendage between the leaf sheaf and blade) is papery, 1-3 mm long and irregularly lobed. The leaves are 2-7 cm long and 0.5-2 mm wide. The leaf surface is ribbed and the leaves taper to an acute point at the end.
Flowers: The inflorescence is a tight panicle, 1.5-5.5 cm long and 0.6-1.6 cm wide. The spikelets (clusters of flowers) are 3-4 mm long and are solitary, the fertile ones having pedicels (stalks) 0.3-2 mm long.
Threats and conservation
It is estimated that fewer than 250 mature individuals of Agrostis trachychlaena exist in the wild, and these are spread over a small area (less than 16 km²), adding to their vulnerability.
It is not known why this species is so rare, although it is thought unlikely to be the result of human activity; erosion of these volcanic islands and subsequent loss of habitat could have played a part. Fire is a potential threat, and a Spartina arundinacea tussock can be easily lit and then burn for a long period.
Visitors to Nightingale Island could introduce alien species, which might pose a further threat, and hence advice on biosecurity is provided to all visitors.
Inaccessible Island is a designated Nature Reserve, out-of-bounds to tourists, as a measure to protect all of its wildlife, including A. trachychlaena.
Conservation assessments carried out at Kew
Agrostis trachychlaena is being monitored as part of the 'IUCN Sampled Red List Index for Plants', which aims to produce conservation assessments for a representative sample of the world’s plant species. This information will then be used to monitor trends in extinction risk and help focus conservation efforts where they are needed most.
Partnerships for conservation
Kew’s UK Overseas Territories (UKOTs) Programme works in collaboration with the Government of Tristan da Cunha Department of Conservation, together with international colleagues from the Netherlands and South Africa.
Fieldwork supported by funds from the European Union and the Overseas Territories Environment Programme (OTEP) enables new herbarium specimens to be collected, including those of Agrostis trachychlaena.
Kew’s UKOTs programme is working with partners to produce a Tristan online herbarium. A seed-collecting programme has been started and the species collected are stored in Kew’s Millennium Seed Bank. A new annotated checklist for the Tristan group is being produced, which includes both native and introduced species.
This species at Kew
The only known dried specimen of Agrostis trachychlaena from Inaccessible Island, was collected by botanist Erling Christophersen, and is housed in the Herbarium at Kew. This is also the type specimen for the species.
Kew also holds specimens of A. trachychlaena collected on Nightingale Island by scientists Nigel M. Wace in the 1970s and Peter Ryan in 2007.
Clayton, W.D., Harman, K.T. & Williamson, H. (2006 onwards). GrassBase - The Online World Grass Flora. (Accessed 10 August 2010). Available online.
Groves, E.W. (1981). Vascular plant collections from the Tristan da Cunha group of islands. Bull. Brit. Mus. (Na. Hist.) 8: 333-420.
Jakubowsky, G. (2003). Agrostis trachychlaena. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.2. <www.iucnredlist.org>. Downloaded on 11 August 2010.
Kew Science Editor: Heather Lindon
Kew contributors: Colin Clubbe, Martin Hamilton
Copyediting: Emma Tredwell
Kew would like to thank the following contributors: Niek Gremmen (Data Analyse Ecologie, Diever, Netherlands)
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