Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
647. RONDELETIA BUXIFOLIA Rubiaceae Plant in Peril, 32 Colin Clubbe, Martin Hamilton and Marcella Corcoran Summary. Rondeletia buxifolia Vahl (Rubiaceae) a critically endangered shrub, restricted to the Caribbean Island of Montserrat, is described and illustrated. Its distribution and conservation status are reviewed. Rondeletia buxifolia Vahl is a small multi-stemmed shrub, restricted to the Caribbean island of Montserrat, a UK Overseas Territory (UKOT). The earliest botanical collections in Montserrat were made by John Ryan in the late 18th century. He lived and worked on the island for many years as a physician and a plantation owner. During this time, Ryan sent many herbarium specimens to the Copenhagen Herbarium in his home country of Denmark. These included the type specimens of R. buxifolia and another Montserrat endemic, the small tree Xylosma serrata Urb. (Salicaceae). Based on Ryan’s collections, M. H. Vahl published R. buxifolia as a new species in 1798. Rondeletia L. is a neotropical genus of small trees and shrubs in the family Rubiaceae. A few species, such as Rondeletia odorata Jacq. and Rondeletia amoena Hemsl. have been brought into cultivation for their colourful flowers and their scented inflorescence. Two hundred and sixty-four species of Rondeletia have been described and are distributed from Mexico to Tropical America and across the Caribbean (Govaerts et al., 2008). One hundred and thirty species have a Caribbean distribution with a centre of diversity in Cuba where 65 species are endemic. Of the Caribbean species, 135 are single island endemics and the smaller islands of Montserrat, Anguilla, St Vincent and Martinique each support a single species. Seventeen species of Rondeletia are listed on the global red list of threatened species (IUCN, 2008). From the late 18th century, Montserrat was little visited by botanists and there are relatively few records of Rondeletia buxifolia, most notably by J.S. Beard in 1944, and by G.R. Proctor in 1959. Richard Howard produced the first extensive checklist of the flora of Montserrat for his Flora of the Lesser Antilles (Howard, 1974–1989). This remains the most Curtis’s Botanical Magazine 2009 vol. 26 (1&2): pp. 131–141 © The Board of Trustees of the Royal Botanic Gardens, Kew 2009. 131 important and comprehensive botanical inventory of Montserrat and the other islands in the Lesser Antilles. Howard’s collections of R. buxifolia in 1979 represent the last known herbarium specimen vouchers of this species collected before the current Kew programme in Montserrat. In 1995, the Soufrière Hills volcano in the south of the island rumbled to life for the first time in more than 400 years. For two years it released gas and ash and there was increased seismic activity and lava dome growth. A major set of explosions in 1997 and dome collapse unleashed a series of pyroclastic flows that buried the capital city of Plymouth and many surrounding villages. Among the losses were the island’s agriculture station and botanic garden together with large areas of natural forest. Today, nearly half the island is an exclusion zone and life is re-establishing itself in the north creating inevitable pressure on the remaining forested areas and their constituent plant and animal species. In 2005 the UK government’s Darwin Initiative funded a collaborative project to undertake a biodiversity assessment of Montserrat’s Centre Hills and to develop a management plan to help guide future conservation activities (www.malhe.gov.ms/centrehills/). This project enabled Kew’s UK Overseas Territories Programme to work with the Montserrat government and the Montserrat National Trust to undertake the first comprehensive botanical assessment of the Centre Hills, and the first major piece of botanical fieldwork in Montserrat since Howard’s pioneering work in the seventies. Over the last three years a series of botanical expeditions has resulted in a good understanding of the plants of Montserrat, their key habitats and how the volcanic eruptions have impacted on them. This has enabled the production of a new vegetation map for Montserrat, a species checklist and candidate red list, with a clearer understanding of the distribution of Montserrat’s most important species for conservation, including Rondeletia buxifolia (Hamilton et al., 2008). The first steps were also taken in indentifying the key threats these species face and the conservation action required for their long-term survival. Much of Montserrat’s 63 km2 is very rugged comprising three distinct volcanic ranges: the oldest geologically is the Silver Hills (to 450 m) in the north, the Centre Hills (to 740 m) and the youngest and currently active volcanic region of the Soufrière Hills (to 900 m) 132 © The Board of Trustees of the Royal Botanic Gardens, Kew 2009. Plate 647 Rondeletia buxifolia (large flowers and leaves × 5) christabel king © The Board of Trustees of the Royal Botanic Gardens, Kew 2009. 135 The northern flanks of the Centre Hills, dominated by Katy Hill (740m). The lower elevation forests in the foreground show typical habitat for Rondeletia buxifolia. Patches of encroaching agriculture are also evident. Photograph: Colin Clubbe. in the south. The vegetation of Montserrat is largely determined by the amount of rainfall, which is in turn closely linked to elevation. Secondary vegetation now covers most of the island due to historical clearance for agriculture, timber and charcoal. Hamilton et al. (2008) identified three major forest types for their vegetation map largely based on a broad moisture gradient and containing a characteristic set of species: Dry Forest types, Mesic Forest types and Wet Forest types. Two further habitats of much more restricted distribution and fewer characteristic species were also identified: Littoral Forest and Elfin Woodland. Inland, at lower altitudes and where rainfall is limited Rondeletia buxifolia grows in the dry scrub or thickets of the Silver Hills. It occurs in stands of Dry Forest (seasonally deciduous sub-tropical woodland) with low rainfall, usually along lower valleys and hill ridges and alongside seasonal stream beds. Mesic Forest begins to appear as more moisture becomes available, usually at moderate elevations and further up along stream beds and is a preferred habitat for R. buxifolia. (Hamilton et al., 2008). R. buxifolia does not occur in Wet Forest types. When growing in the shade and shelter of other species, R. buxifolia has an elongated and spindly habit, with soft lush green leaves; however, it will eventually fall over, reaching the ground and producing new roots on the stem thus creating a new plant. The opposite is true for the individuals growing in full sun, which produce a sturdy compact shrub with thicker stems and leaves able to withstand the harsh environment of sun and wind. Individuals growing in full sun flower earlier and much more profusely, with flowering declining as shade increases indicating a preference for forest edge habitats. An analysis by Jones (2008) showed sexual reproduction, as indicated by fruit presence, to be predominantly positively influenced by increasing light levels. A recent study has shown that Rondeletia buxifolia is more widespread within the Silver Hills than was originally realised and has provided a better understanding of its distribution outside the Centre Hills (Jones, 2008). Jones (2008) also calculated a total extent of occurrence (sensu IUCN, 2001) of R. buxifolia to be 16.6 km2 . The only forest area in Montserrat currently under legal protection is the Centre Hills Forest Reserve which comprises an area of approximately 1110 ha occupying the central areas of the Centre Hills range above an elevation of approx 200 m. Although an important protected area 136 © The Board of Trustees of the Royal Botanic Gardens, Kew 2009. Legend: Rondeletia buxifolia points Contours Forest Reserve boundary Volcanic deposits Scale: 1 cm = 1.4 Km Map of Montserrat, showing recorded locations of Rondeletia buxifolia. Drawn by M.A. Hamilton. for many Montserrat species and for watershed protection, ∼ 90% of the population of R. buxifolia is located outside the Forest Reserve and afforded no real protection. However, a new Conservation and Environmental Management Bill is being drafted which will offer species level protection to Montserrat’s key species, including R. buxifolia. The Bill is due to be enacted in 2009. © The Board of Trustees of the Royal Botanic Gardens, Kew 2009. 137 There is great concern for the long-term survival of Rondeletia buxifolia, due to a decline in suitable habitat attributable to: • Volcanic eruptions which threaten the Dry and Mesic Forest habitats. Apart from pyroclastic flows which destroy everything in their path, volcanic ash and acid rain defoliate the vegetation, leading to a decline in the number of individuals. • Pressure from residential infrastructure and tourism development resulting in direct loss, degradation and fragmentation of suitable habitat. • Alien invasive plant species including Psidium guajava L. and Cryptostegia madagascariensis Bojer ex Decne. These species compete aggressively with native vegetation and are spreading rapidly, causing serious damage to habitats and species. A recent study used prediction mapping of the spread of these two species and showed a near complete overlap with the habitat requirements of R. buxifolia which could result in the virtual elimination of this species from Montserrat should the spread of these invasive species remain unchecked (Stow, 2008). • Pressure from feral livestock poses a major threat to the R. buxifolia, in particular the goats roaming in the Silver Hills, which chew plants to the ground, severely limiting regeneration. The effect that rats have on seedling regeneration is currently unknown, but is under investigation. • Climate change has the potential to change the climatic envelope of R. buxifolia with as yet unknown effects. Based on knowledge of the distribution of Rondeletia buxifolia and the threats that the species is facing Hamilton et al. (2008) suggested a candidate red list status of critically endangered. Data provided by Jones (2008) has confirmed this assessment and enabled R. buxifolia to be formally assessed as Critically Endangered B1ab(iii, v) based on the IUCN red list criteria (IUCN, 2001). Conservation Measures. An integrated conservation strategy is being developed for R. buxifolia involving both ex situ and in situ conservation measures, plus raising awareness about the status and importance of this species. The UK government’s Overseas Territories Environment Programme (OTEP) have recently funded a 138 © The Board of Trustees of the Royal Botanic Gardens, Kew 2009. project to enable species action plans to be developed in a participatory way with local stakeholders in Montserrat for the most important species of plants, amphibians, reptiles and mammals. These follow the successfully completed action plant for the critically endangered Montserrat oriole (Hilton et al., 2005). The workshop to develop a species action plan for Montserrat’s endemic plants was held in 2008 and a draft action plan is in circulation for comment. Recommended conservation actions build on those currently under way. In 2006 seed of Rondeletia buxifolia was collected for long-term seed banking at Kew’s Millennium Seed Bank (MSB). The seed was collected from within the Centre Hills Forest Reserve and sent to the MSB for banking. This collecting was undertaken as part of a broader conservation strategies training workshop to help build conservation capacity in Montserrat, and seeds of other critical species have been collected for the MSB since then. A portion of the seed lot of R. buxifolia was sent to Kew to be used to develop a horticulture protocol. The UKOT Programme is engaged in developing full horticulture protocols for UKOT’s threatened species, and training local counterparts is part of their core activity (Hamilton et al., 2007; Corcoran et al., 2008). This is also contributing directly to meeting the targets of the Global Strategy for Plant Conservation (GSPC, 2002). The horticulture protocol has been completed and sent to the Montserrat National Trust (Corcoran et al., 2008). Kew has been helping the Montserrat National Trust to establish a new botanic garden at its headquarters in the north of the island in a project also funded by OTEP. The Trust’s original offices in Plymouth were destroyed by the 1997 volcanic eruptions as was the island’s original botanic garden. A new nursery has been completed and several of Montserrat’s threatened and culturally important plant species are in cultivation there. Observations on the growth form of R. buxifolia in the wild suggested that it would make a good hedging plant and a trial hedge has been planted out at the Montserrat Botanic Garden. Early indications from this trial are very positive and a plan is being developed to supply plants for the Montserrat general public to encourage wider use of this species in landscaping. This would have several benefits. An endemic species being used in a sustainable way would be a flagship for conservation awareness. It could replace non-native species of Ficus currently widely used for © The Board of Trustees of the Royal Botanic Gardens, Kew 2009. 139 F E A C D B Rondeletia buxifolia. A, leaf (largest), × 1; B, growing point with buds and two leaves, × 2; C, node with buds, × 4; D, l.s. flower, × 4; E, style, × 8; F, t.s. ovary, × 10. Drawn by Christabel King from living material at Kew. hedging which has detrimental impacts on the soil and provide an unfriendly environment for local biodiversity. In the short-term the outlook for R. buxifolia is quite positive. Its future has been secured ex situ by long-term seed banking in the MSB, and by cultivation in Montserrat and at Kew. However, its future in situ remains precarious, as habitat is lost and individuals destroyed as the infrastructural demands of a re-establishing nation in the north of the island clash with the centre of diversity for this critically endangered species. Rondeletia buxifolia Vahl, Eclogae Americanae ii. 11, t. 12 (1798). Type: habitat in Montserrat. Ryan (C). Description. A lax or dense shrub 1–3 m tall, with slender arching branches. Stipules subannular, 1 mm long, strigillose. Leaf petioles 1–2 mm long; blades cuneate-obovate to spathulate, 1.3–3.5 × 0.7–1.7 cm, base cuneate, apex rounded or retuse, glabrous or appressed pubescent on the veins at the leaf base. Inflorescence axillary, 1- to 3-flowered, pedicels to 2 mm; calyx lobes 4, linear or oblanceolate, 1.5–3 mm long, acute; corolla salveri form, tube 6–7 mm, cream or buff to yellowish, retrorsely pubescent outside, lobes 4, 1.5–2 mm long. Capsules sub-globose, 4 mm in diameter, tomentulous; seeds 1 mm long, angulate, reticulate, winged (adapted from Howard, 1989 p.456). 140 © The Board of Trustees of the Royal Botanic Gardens, Kew 2009. Distribution. Caribbean: restricted to Montserrat. Habitat. Restricted to an area of 16.6 km2 in the north of the island in Dry Forest (seasonally deciduous sub-tropical woodland), Dry Scrub, and Mesic Forest at low elevations. Conservation status. Critically Endangered B1ab(iii, v). REFERENCES Corcoran, M.R., Robbins, S.K., Hamilton, M.A. & Clubbe, C. (2008). Report on the Status of Rondeletia buxifolia Vahl., Including a Germination and Cultivation Protocol. Internal Report, Royal Botanic Gardens, Kew. Govaerts, R., Ruhsam, M., Andersson, L., Robbrecht, E., Bridson, D., Davis, A., Schanzer, I. & Sonké, B. (2008). World Checklist of Rubiaceae. The Board of Trustees of the Royal Botanic Gardens, Kew. Published on the Internet; www.kew.org/wcsp/rubiaceae/. Downloaded on 10 November 2008. GSPC (2002). Global Strategy for Plant Conservation. Published by the Secretariat of the Convention on Biological Diversity. Available at: www.cbd.int/gspc/. Hamilton, M.A., Clubbe, C., Robbins, S.K. & Bárrios, S. (2008). Plants and habitats of the Centre Hills and Montserrat. In: Young, R.P. (ed.), A Biodiversity Assessment of the Centre Hills, Montserrat. Durrell Conservation Monographs, Vol. 1, pp. 40–55. Downloadable from www.durrell.org/Conservation/Where-wework/Caribbean-Islands/. Hamilton, M.A., Robbins, S.K., Johnson, N.P., Sanchez, M.D. & Clubbe, C. (2007). Report on the status of Acacia anegadensis Britton Including a Germination and Cultivation Protocol. Unpublished Report, RBG Kew. Available at: www.kew.org/scihort/ukots/Pages/bvi2bi.htm. Hilton, G.M., Gray, G.A.L., Fergus, E., Sanders, S.M., Bloxam, Q., Clubbe, C. & Ivie, M. (eds.) (2005). Species Action Plan for the Montserrat oriole, Icterus oberi, 2005–2009. Department of Agriculture, Montserrat. Howard, R.A. (1974–1989). Flora of the Lesser Antilles: Leeward and Windward Islands. 6 volumes. Arnold Arboretum, Harvard University, Jamaica Plain, USA. Howard, R.A. (1989). Rondeletia buxifolia Vahl. Flora of the Lesser Antilles: Leeward and Windward Islands. vol. 6 Dicotyledoneae (Part. 3). Arnold Arboretum, Harvard University, Jamaica Plain, USA. p. 456–457. IUCN (2001). IUCN Red List Categories version 3.1. IUCN Species Survival Commission, IUCN. Gland and Cambridge. Available at: www.iucnredlist.org/static/categories_criteria. IUCN (2008). 2008 IUCN Red List of Threatened Species. www.iucnredlist.org. Downloaded on 10 November 2008. Jones, M. (2008). Distribution and Conservation of Montserrat’s Endemic Flora. Unpublished MSc thesis Imperial College, London. Stow, S. (2008). Non-Native Plant Distribution in Montserrat: Conservation and Ecological Aspects. Unpublished MSc thesis Imperial College, London. © The Board of Trustees of the Royal Botanic Gardens, Kew 2009. 141