|Scientific Name:||Commidendrum robustum (Roxb.) DC.|
Aster roxburghii Hook.f.
Commidendrum robustum (Roxb.) DC subsp. robustum
Conyza robusta Roxb.
|Taxonomic Notes:||Commidendrum forms a monophyletic endemic genus with no very close affinities (Noyes and Reiseberg 1999).
The Gumwood (Commidendrum robustum (Roxb.) DC.) was split into two subspecies by Cronk (2000):
Some of the specimens labelled as C. gummiferum lie within the range of variation exhibited by C. robustum subsp. robustum. The remainder certainly belong to a distinct taxon, but their classification as a subspecies is difficult to reconcile with the fundamental differences in flower and inflorescence structure from subsp. robustum. In fact, they are somewhat closer to the False Gumwood (C. spurium (G.Forst) DC.). For this reason, the current treatment restores C. gummiferum as a species, though uncertainties persist over its true position, and there is a strong possibility that it may be a hybrid between the two surviving parents.
The well-defined C. robustum is thus retained as a species concept without division at subspecific level. Subspecies gummiferum has been promoted to species level under C. gummiferum, along with the Red List assessment done by Q. Cronk in 1998.
|Red List Category & Criteria:||Critically Endangered B1ab(v)+2ab(v) ver 3.1|
|Assessor(s):||Ellick, S. & Lambdon, P.W.|
Although planted as an ornamental and landscaping tree in various parts of the island, Gumwood (Commidendrum robustum
(a) The population can be considered severely fragmented as the two extant sites are highly isolated from each other and juveniles are apparently unable to establish in the surrounding habitat.
(b) Direct evidence of a decline is limited as previous census data do not date back beyond the current generation of trees. However, we infer that future declines in the number of mature individuals are inevitable based on the similar age structure of the surviving population (most trees are now reasonably old), and low levels of regeneration at the existing sites. There has also been an observed loss of some scattered remnant wild trees from outlying localities over the past few decades.
|Previously published Red List assessments:|
The extent of occurrence (EOO), based on the area of a minimum convex polygon around known localities, is 20.4 km2. The area of occupancy (AOO), based on a 2 km × 2 km grid, is 8 km2.
Native:Saint Helena, Ascension and Tristan da Cunha (Saint Helena (main island))
|Range Map:||Click here to open the map viewer and explore range.|
A census conducted in 2013 – 14 calculated the wild Gumwood population at 679 mature trees through direct counts at each wild site, with 97.6% of the total world population contained within the Peak Dale site, and the remaining 2.4% at Deep Valley.
|Current Population Trend:||Decreasing|
|Habitat and Ecology:|
A species of St Helena’s mid-altitudinal range. Several sources of evidence suggest that dense Gumwood forest once covered extensive areas of the island. Gumwood occupied moderately damp soils up to 600 m elevation, but also extended across drier plateaus and ridges down to 400 m, showing substantial resilience to dry conditions. Numerous isolated individuals persisted on cliffs and rocky outcrops well into the 1800s, though few remain today.
|Use and Trade:||
The species has been used in the past for timber and fuel. Currently used for craft products including photo frames, with potential for more of this kind of utilization in the future.
The vast tracts of Gumwood woodland largely disappeared in well under a century following the establishment of a permanent British colony on St Helena in 1659. The principle cause of the losses were probably land clearances to make way for pasture, and the felling of trees for firewood and (less suitably) for timber. At the same time, foliage was browsed by goats (Capra hircus) and seedlings uprooted by the numerous wild pigs (Sus domesticus) and cattle (Bos taurus). These large vertebrate herbivores have now largely been eradicated on the island.
Both extant sites are protected under the recently designated National Conservation Area (NCA) network. Peak Dale is located the Peaks National Park, and the Deep Valley subpopulations fall within the Deep Valley Nature Reserve. Development Plans for all NCAs are currently in development and will be legal documents. The species will also be protected under new legislation: the Environmental Protection Ordinance, which is expected to come into effect in late 2016 and will supersede the current Endangered Species Ordinance.
|Citation:||Ellick, S. & Lambdon, P.W. 2016. Commidendrum robustum. The IUCN Red List of Threatened Species 2016: e.T37583A67370371.Downloaded on 22 November 2017.|
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