Trochetiopsis ebenus 

Scope: Global
Status_ne_offStatus_dd_offStatus_lc_offStatus_nt_offStatus_vu_offStatus_en_offStatus_cr_onStatus_ew_offStatus_ex_off

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Taxonomy [top]

Kingdom Phylum Class Order Family
Plantae Tracheophyta Magnoliopsida Malvales Sterculiaceae

Scientific Name: Trochetiopsis ebenus
Species Authority: Cronk
Common Name(s):
English Dwarf ebony, Ebony, St Helena Ebony
Synonym(s):
Melhania melanoxylon sensu Melliss non R.Br.
Trochetiopsis melanoxylon (R.Br. ) Marais non Cronk

Assessment Information [top]

Red List Category & Criteria: Critically Endangered D ver 3.1
Year Published: 2016
Date Assessed: 2015-06-16
Assessor(s): Lambdon, P.W. & Ellick, S.
Reviewer(s): Clubbe, C.P.
Contributor(s): Cairns-Wicks, R.
Justification:
Although Dwarf Ebonies (Trochetiopsis ebenus) are now widely cultivated on St Helena and have been reintroduced to semi-natural situations, there is only one surviving group of wild plants which covers no more than 100 m2. Given these extreme circumstances, the species must qualify as Critically Endangered under criterion D. It has persisted at very low numbers since the first records for it appear in the early 1800s, and thus there is no evidence that the decline is recent or ongoing. This precludes full qualification under criteria A, B and C.
Previously published Red List assessments:

Geographic Range [top]

Range Description:The Dwarf Ebony is found in the wild only at a single locality on the south-western coastal hills of St Helena, South Atlantic Ocean.

The extent of occurrence (EOO), based on the area of a minimum convex polygon around known localities, is 100 m2. The area of occupancy (AOO), based on a 2 km × 2 km grid, is 4 km2. Following IUCN Red List Guidelines, the EOO is therefore increased to 4 km2 to match the AOO.

The only extant site is a phonolytic cliff on the eastern side of Blue Point Ridge. The bluff is now sometimes known as ‘Ebony Point’.

There is very little evidence from which the original range can be reconstructed. The only previous wild localities which can certainly be attributed to this species were noted by W.J. Burchell in the early 19th Century, at High Hill and Man & Horse. These two historical and the modern site lie within a 2 km radius in the south-western part of St Helena, between 500 and 700 m altitude. Other locations mentioned in 18th Century references (e.g. High Knoll, The Barn) would extend the range across drier coastal hills over almost the entire island, but it is unclear whether these early records refer to T. ebenus or T. melanoxylon.
Countries occurrence:
Native:
Saint Helena, Ascension and Tristan da Cunha (Saint Helena (main island))
Additional data:
Estimated area of occupancy (AOO) - km2:4Continuing decline in area of occupancy (AOO):No
Extreme fluctuations in area of occupancy (AOO):NoEstimated extent of occurrence (EOO) - km2:4
Continuing decline in extent of occurrence (EOO):NoExtreme fluctuations in extent of occurrence (EOO):No
Number of Locations:1Continuing decline in number of locations:No
Extreme fluctuations in the number of locations:NoLower elevation limit (metres):500
Upper elevation limit (metres):700
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:The current wild population numbers just two mature individuals and three juveniles. The juveniles may have self-seeded since 1980, when the site was discovered by George and Charlie Benjamin and Quentin Cronk (see Cronk 2000). Prior to this, the species was thought to have been extinct since 1850, when a garden plant was noted at Oakbank by J.C. Melliss (Melliss 1875).
Current Population Trend:Stable
Additional data:
Number of mature individuals:2Continuing decline of mature individuals:No
Extreme fluctuations:NoPopulation severely fragmented:No
No. of subpopulations:1Continuing decline in subpopulations:No
Extreme fluctuations in subpopulations:NoAll individuals in one subpopulation:Yes

Habitat and Ecology [top]

Habitat and Ecology:

Known locations suggest that the Dwarf Ebony is a species of arid coastal hill tops. It is resilient to dry conditions, but appears to be less tolerant of strong winds or prolonged drought than other endemic shrubs of St Helena’s dryland zone, e.g. Scrubwood (Commidendrum rugosum (Aiton). DC.), and fares better in sheltered locations with less arid soils, provided there is little competition from taller species.

The low, shrubby growth form typically reaches one metre high (occasionally more). Under favourable conditions, flowering may occur throughout the year. The large, attractive flowers are self-fertile but produce copious pollen and nectar and are visited by a wide range of insects. The seeds are relatively large with no specialized adaptations for dispersal, and most fall near the parent. They are probably predated by mice (Mus musculus) in wild situations. The duration of viability is unknown.

Systems:Terrestrial
Continuing decline in area, extent and/or quality of habitat:No
Movement patterns:Not a Migrant

Use and Trade [top]

Use and Trade: The Dwarf Ebony has recently been adopted as St Helena’s national flower and thus has symbolic and cultural value. It makes an excellent garden plant but has not yet been widely grown outside the island. Specimens propagated at the government plant nursery (now managed by the Environmental Conservation Section) have been made freely available to the public and plants are swapped by local gardeners. Thus, although popular as an ornamental, the commercial trade is minimal.

Threats [top]

Major Threat(s):

The almost total annihilation of the species occurred before 1800, and as this pre-dates most of the botanical records of St Helena, there is little direct evidence to determine its cause. However, very high levels of goat grazing were very likely to have been a major factor. Goats (Capra hircus) were introduced by Portuguese sailors in the early 16th Century and thrived in large numbers until their virtual eradication in the 1950-70s. During the intervening period, much of the island’s native vegetation cover was lost from the mid-altitude hills. Other invasive herbivores such as rabbits (Oryctolagus cuniculus), rats (Rattus rattus  and R. norvegicus) and mice may have had further impacts on seed and seedling regeneration.

Today, the wild plants at Ebony Point do not appear to face any pressing threats, although invasive shrubs such as Black Olive (Olea europaea subsp. africana (Mill.) P.Green) and Wild Mango (Schinus terebinthifolia Raddi) have encroached onto the cliff and could eventually become problematic if establishing too close to any of the specimens. One of the juveniles has died back considerably since 2011, when photographs showed it to be a much larger plant. The reasons for its deterioration are unclear, but could be related to a drought in 2013. The population is too small to permit any chance of widespread natural recovery.

Conservation Actions [top]

Conservation Actions:

Cuttings were collected from one plant at Ebony Point soon after the Dwarf Ebony was rediscovered in 1980, following a daring cliff descent on a rope and makeshift harness by Charlie Benjamin. In 2008, further collections were made from the second plant by Mike Thorsen. The species also grows well from seed, and has now been propagated very successfully. Today, there are a few thousand specimens on St Helena, mostly in gardens and at sites where attempts have been made to restore the species to wild situations. The main reintroduction sites include Ebony Plain (approximately 840 surviving plants), High Peak (130 plants) and the Millennium Forest (several hundred).

Unfortunately, the species' ecological requirements were little understood when the restoration efforts commenced, and problems have subsequently been noted in all situations. Habitats at Ebony Plain and the Millennium Forest are both very barren with dry soils, and although specimens have survived, flowered and seeded well in both cases, the natural recruitment has been close to zero. Conversely, High Peak was chosen as a humid, upland location, and here, the low canopies have been largely overgrown by vigorous invasive grasses. It is likely that the habitat requirements are rather specific, and suitable areas may now be limited following the extensive degradation of coastal hills and colonization of the higher elevations by dense non-native vegetation. More establishment trials in a wider range of locations are needed to determine whether a suitable niche can be found, thus allowing the species can become self-sustaining. One such initiative is currently under way at High Hill, where attempts have been made to populate the species on grassy slopes and open pine forest. Meanwhile, seed has added to long-term storage on-island and at Kew's Millennium Seed Bank in the UK.

An additional obstacle to the early reintroduction efforts arose from the risk of hybridization. Crosses between Trochetiopsis ebenus and the congeneric Redwood (T. erythroxylon (G.Forst.) Marais) are fully fertile and easily produced by natural cross-pollination if the two species are grown in close-proximity. Many specimens of the 'Rebony' (T. ebenus × erythroxylon) were inadvertently introduced to Ebony Plain and High Peak. Since the issue was recognized, protocols have been established to avoid further genetic contamination, and removal of Rebonies from problem situations is encouraged where necessary.

Plans to establish a Sandy Bay National Park are currently in development, and the protected zone will encompass Ebony Point. The species will also be protected under the new Environmental Protection Ordinance, presently in the final stages of drafting and expected to be issued in 2016. However, as the extant population occurs on a sheer cliff, it already suffers little threat from human interference.

Classifications [top]

3. Shrubland -> 3.5. Shrubland - Subtropical/Tropical Dry
suitability:Suitable  
3. Species management -> 3.2. Species recovery
3. Species management -> 3.3. Species re-introduction -> 3.3.1. Reintroduction
4. Education & awareness -> 4.1. Formal education
4. Education & awareness -> 4.2. Training

In-Place Research, Monitoring and Planning
  Action Recovery plan:Yes
  Systematic monitoring scheme:No
In-Place Land/Water Protection and Management
  Conservation sites identified:Yes, over entire range
  Occur in at least one PA:Yes
  Percentage of population protected by PAs (0-100):91-100
In-Place Species Management
  Successfully reintroduced or introduced beningly:No
  Subject to ex-situ conservation:Yes
In-Place Education
  Subject to recent education and awareness programmes:Yes
  Included in international legislation:Yes
  Subject to any international management/trade controls:No
2. Agriculture & aquaculture -> 2.1. Annual & perennial non-timber crops -> 2.1.2. Small-holder farming
♦ timing:Past, Unlikely to Return ♦ scope:Unknown ♦ severity:Unknown ⇒ Impact score:Past Impact 
→ Stresses
  • 1. Ecosystem stresses -> 1.1. Ecosystem conversion
  • 2. Species Stresses -> 2.1. Species mortality

5. Biological resource use -> 5.3. Logging & wood harvesting -> 5.3.1. Intentional use: (subsistence/small scale)
♦ timing:Past, Unlikely to Return ♦ scope:Unknown ♦ severity:Unknown ⇒ Impact score:Past Impact 
→ Stresses
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation
  • 2. Species Stresses -> 2.1. Species mortality
  • 2. Species Stresses -> 2.2. Species disturbance

8. Invasive & other problematic species & genes -> 8.1. Invasive non-native/alien species -> 8.1.1. Unspecified species
♦ timing:Ongoing ♦ scope:Whole (>90%) ♦ severity:Slow, Significant Declines ⇒ Impact score:Medium Impact: 7 
→ Stresses
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation
  • 2. Species Stresses -> 2.3. Indirect species effects -> 2.3.2. Competition

8. Invasive & other problematic species & genes -> 8.1. Invasive non-native/alien species -> 8.1.2. Named species [ Capra hircus ]
♦ timing:Past, Unlikely to Return ♦ scope:Majority (50-90%) ♦ severity:Rapid Declines ⇒ Impact score:Past Impact 
→ Stresses
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation
  • 1. Ecosystem stresses -> 1.3. Indirect ecosystem effects
  • 2. Species Stresses -> 2.1. Species mortality
  • 2. Species Stresses -> 2.3. Indirect species effects -> 2.3.7. Reduced reproductive success

8. Invasive & other problematic species & genes -> 8.1. Invasive non-native/alien species -> 8.1.2. Named species [ Oryctolagus cuniculus ]
♦ timing:Ongoing ♦ scope:Majority (50-90%) ♦ severity:Negligible declines ⇒ Impact score:Low Impact: 5 
→ Stresses
  • 2. Species Stresses -> 2.3. Indirect species effects -> 2.3.8. Other

12. Other options -> 12.1. Other threat
♦ timing:Ongoing ♦ scope:Whole (>90%) ♦ severity:Unknown ⇒ Impact score:Unknown 
→ Stresses
  • 1. Ecosystem stresses -> 1.3. Indirect ecosystem effects

1. Research -> 1.3. Life history & ecology
1. Research -> 1.6. Actions
2. Conservation Planning -> 2.2. Area-based Management Plan
3. Monitoring -> 3.1. Population trends
3. Monitoring -> 3.4. Habitat trends

Bibliography [top]

Antommarchi, F.C. 1825. Esquisse de la flore de Sainte Hélène. Barrois l’Aine, Paris.

Burchell, W.J. 1805-10. Flora Insulae Sanctae Helenae. Unpublished manuscript held at Royal Botanic Gardens Kew, Richmond, U.K.

Cairns-Wicks, R. 2003. Trochetiopsis ebenus. The IUCN Red List of Threatened Species 2003: e.T37855A10082104. doi: /10.2305/IUCN.UK.2003.RLTS.T37855A10082104.en.

Cairns-Wicks, R. Draft Recovery Action Plan for Trochetiopsis ebenus (Sterculiaceae).

Cronk, Q.B.C. 1986. The decline of the St Helena ebony Trochetiopsis melanoxylon. Biological Conservation 35: 159-172.

Cronk, Q.B.C. 1995. A new species and hybrid in the St Helena endemic genus Trochetiopsis (Sterculiaceae). Edinburgh Journal of Botany 52: 205-213.

Cronk, Q.C.B. 2000. The Endemic Flora of St. Helena. Anthony Nelson Publishers, Oswestry, UK.

IUCN. 2016. The IUCN Red List of Threatened Species. Version 2016-1. Available at: www.iucnredlist.org. (Accessed: 30 June 2016).

Lambdon, P. 2012. Flowering Plants and Ferns of St Helena. Pisces Publications, Newbury, UK.

Melliss, J.C. 1875. St Helena: A Physical, Historical and Topographical Description of the Island, Including its Geology, Fauna, Flora and Meteorology. L. Reeve & Co., London, U.K.

Rowe, R. 1995. The population biology of Trochetiopsis: a genus endemic to St Helena. Unpublished PhD thesis, University of Oxford, Oxford, U.K.

Royal Botanic Gardens, Kew. 2009. Data extracted from notes accompanying collection of herbarium specimens. Accessed 2009. Royal Botanic Gardens, Kew, London.


Citation: Lambdon, P.W. & Ellick, S. 2016. Trochetiopsis ebenus. In: The IUCN Red List of Threatened Species 2016: e.T37855A67371855. . Downloaded on 30 August 2016.
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