Commidendrum spurium 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Plantae Tracheophyta Magnoliopsida Asterales Asteraceae

Scientific Name: Commidendrum spurium (G.Forst.) DC.
Common Name(s):
English False Gumwood
Aster gummiferus Hook.f. pro parte
Conyza cuneifolia Raeusch. non Lam.
Solidago spuria G.Forst.

Assessment Information [top]

Red List Category & Criteria: Critically Endangered B1ab(i,ii,iii,iv,v)+2ab(i,ii,iii,iv,v); C1+2a(i,ii); D ver 3.1
Year Published: 2016
Date Assessed: 2015-06-12
Assessor(s): Lambdon, P.W. & Ellick, S.
Reviewer(s): Clubbe, C.P.
Contributor(s): Cairns-Wicks, R.
As there is only one extant patch of seven plants, the False Gumwood (Commidendrum spurium) easily qualifies for listing as Critically Endangered under the range and population size criteria of B1+2, C1+2 and D. The decline in numbers within the current generation is at least 30%, and there is no reason to assume that this is not part of an ongoing trend. This fulfills the remaining subcriteria under both B and C. The reduction of the species to this small remnant population is due to past habitat clearance for agricultural expansion (creation of pasture and cultivation of New Zealand Flax), use of the species as firewood or for timber and the ongoing impacts of various introduced and invasive plant and animal species.
Previously published Red List assessments:

Geographic Range [top]

Range Description:

The False Gumwood is restricted to the western Central Ridge of St Helena, South Atlantic Ocean.

The extent of occurrence (EOO), based on the area of a minimum convex polygon around known localities, is 402 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.

This highly threatened species was more widespread along the western part of St Helena’s Central Ridge in the 19th Century, although even by this time it appears to have been very rare. Today is confined to a single rock outcrop at Mt Vesey.

Countries occurrence:
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):Yes
Extreme fluctuations in area of occupancy (AOO):NoEstimated extent of occurrence (EOO) - km2:4
Continuing decline in extent of occurrence (EOO):YesExtreme fluctuations in extent of occurrence (EOO):No
Number of Locations:1Continuing decline in number of locations:Yes
Extreme fluctuations in the number of locations:NoLower elevation limit (metres):650
Upper elevation limit (metres):750
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:In 1983, the world population numbered 10 individuals at three sites. At the time of the previous Red List assessment (Cairns-Wicks 2003), this had declined to eight plants at two sites, and since then, it has again declined to six individuals. The single tree on a cliff at Sheep Pound (near Cole’s Rock) died in 2013, leaving the remaining population confined to Mt Vesey. The surviving plants may also be displaying signs of ageing.
Current Population Trend:Decreasing
Additional data:
Number of mature individuals:6Continuing decline of mature individuals:Yes
Extreme fluctuations:NoPopulation severely fragmented:No
No. of subpopulations:1
Extreme fluctuations in subpopulations:NoAll individuals in one subpopulation:Yes

Habitat and Ecology [top]

Habitat and Ecology:

Over the last century there have never been more than a few known individuals in existence and many details of the species’ ecology therefore remain unknown. Of the four extant species in the endemic genus Commidendrum, the False Gumwood appears to have had the most montane distribution, with all recorded wild plants occurring between 650 and 750 m altitude. It is not entirely clear what the associated vegetation would have looked like. The elevation range lies somewhere between a belt thought to have been dominated by upland gumwood forest and the true cloud forest zone nearer the summits, dominated by cabbage  trees (Asteraceae spp.) and Tree Ferns (Dicksonia arborescens L’Hér). However, the original habitat has been entirely destroyed, largely as a result of the large-scale replacement of native upland forest with plantations of New Zealand Flax (Phormium tenax J.R.Forst. & G.Forst.) in the late 19th and early 20th Centuries.

The False Gumwood is a small tree which flowers well in late summer, and occasionally at other times when conditions are favourable (probably determined by a combination of moisture availability, warmth and abatement of the persistent winter winds). It is an outbreeding species with a genetic self-incompatibility mechanism centred around two positions on the genome. Pollen arriving on the stigma of another flower will be destroyed if it is genetically-identical in both loci. There is sufficient diversity of alleles within the surviving individuals to ensure high cross-fertility (Eastwood and Cronk 2002), but further losses could result in extinction of essential genotypes.

Continuing decline in area, extent and/or quality of habitat:Yes
Generation Length (years):100
Movement patterns:Not a Migrant

Use and Trade [top]

Use and Trade: Would have been used as firewood and for timber by early settlers.

Threats [top]

Major Threat(s):

The main cause of decline in the population seems to have been severe habitat loss. Following the establishment of a permanent colony on St Helena in 1658, human exploitation has resulted in heavy reductions to the island's original upland vegetation. Initial impacts arose from conversion of land to pasture, and felling of native woody species for firewood. The establishment of extensive New Zealand Flax plantations along the least productive, steep slopes of the Central Ridge probably cause further, heavy tolls in the late 19th and early 20th Centuries. In subsequent decades, this has been further compounded by smaller-scale habitat deterioration as a result of invasion by non-native shrubs, herbs and grasses. Typically for Asteraceae species,  the fruits are small, wind-blown achenes with a pappus. Grass swards provide intense competition for small germinating seedlings and form a barrier which prevent the achenes from coming into contact with the ground.

In addition, the False Gumwood is particularly vulnerable to invertebrate herbivores. Whilst established adult plants seem to be relatively resilient to pest outbreaks, saplings reintroduced to the wild from cultivation have a poor survival rate. At experimental transplant sites, the main culprits are Rose Weevils (Otiorhynchus spp., Curculionidae), Mealybug (Pseudococcus spp., Pseudococcidae), and black sooty moulds which thrive on the honeydew excreted by the mealybugs, coating the leaf surfaces and reducing photosynthesis. Snails, slugs and caterpillars of moths such as the Ni Moth (Trichoplusia ni Hübner, Noctuidae) are also problematic. It is not clear whether the False Gumwood  has always been highly susceptible to invertebrate damage or whether the vulnerability is a symptom of inbreeding depression.

Conservation Actions [top]

Conservation Actions:

The Mt Vesey site has recently been designated as part of the Central Peaks National Park. Routine weed clearance is conducted twice a year by staff of the island’s Environmental Conservation Section (St Helena Government), and seed collections have been made from all extant individuals. This has been banked on-island and also at Kew's Millennium Seed Bank in the UK. Unfortunately, due to the challenging location, only very small quantities of seed were obtained from the Sheep Pound tree before it died, but an additional collection made from an additional tree which grew at Oaklands in the 1990s has recently been repatriated to St Helena from the Royal Botanic Gardens, Edinburgh.

A species action plan has been prepared by Cairns-Wicks (2009). The seed of False Gumwood has a relatively high germinability and, if carefully tended, plants exhibit moderate survival in cultivation. Due to the difficulties with reintroducing these to the wild, it is essential that a managed seed orchard is established. Care must be taken to ensure that the original genetic diversity is preserved by maintaining propagated specimens of all parents (ideally from cuttings and seed), and also that cross-pollinations between the different parental stocks are performed on a regular basis. If the latter measures are not achieved, then problems of self-incompatibility will eventually develop and increasing genetic impoverishment could have an increasing impact on the health and vigour of future offspring.

Citation: Lambdon, P.W. & Ellick, S. 2016. Commidendrum spurium. The IUCN Red List of Threatened Species 2016: e.T37588A67370705. . Downloaded on 22 May 2018.
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