|Scientific Name:||Nesohedyotis arborea (Roxb.) Bremek.|
Hedyotis arborea Roxb.
|Taxonomic Notes:||Endemic genus of the Hedyotideae, resembling East African genera Hedythyrsus and Pseudonesohedyotis (Tennant 1965), which are small shrubs and not small trees like Nesohedyotis.|
|Red List Category & Criteria:||Critically Endangered A2a; B1ab(iii,v)+2ab(iii,v); C1+2a(i); D ver 3.1|
|Assessor(s):||Ellick, S. & Lambdon, P.W.|
Dogwood (Nesohedyotis arborea) has a very restricted distribution, confined to two fragments of cloud forest which are both less than 2 km across. Although a number of nursery-grown plants have been reintroduced to natural situations, the rate of sapling recruitment remains very low and the total population of truly wild plants has declined to less than 50 mature individuals. This represents a fall of approximately 72% over less than one generation (about 100 years), qualifying the species as Critically Endangered under criteria A2 and C1. As there is no opportunity for cross colonization between sites, and neither population is likely to be stable in the long-term, the distribution can be considered severely fragmented and thus also meets the necessary thresholds under both B1 and B2.
|Previously published Red List assessments:|
Endemic to St Helena Island, South Atlantic Ocean.
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 2013 – 14 census estimated the number of truly wild mature Dogwoods to number just 47 individuals; 24 of these were located in the High Peak area (55.3% of the total population) where they occupy a very restricted expanse of suitable habitat, covering approximately 8.8 ha of cliff face hemmed between pasture and flax stands. The rest (44.7%) are very thinly scattered over a much larger area along Diana’s Peak Ridge. This represents a decline in this species of 72% over less than one generation, from approximately 132 individuals in the mid-1990s (Cairns-Wicks 2003). Counts are somewhat uncertain due to the difficulty of distinguishing Dogwood from the unrelated but superficially very similar Whitewood (Petrobium arboreum (J.R.Forst. & G.Forst.) R. Br.).
|Current Population Trend:||Decreasing|
|Habitat and Ecology:||Found in damp Tree Fern thicket and cabbage tree woodland, the Dogwood is well-adapted to the cloud forest zone. Although the natural distribution is somewhat obscured by recent plantings, surviving wild trees are most commonly found in dense thickets of cabbage trees, ranging from sheltered slopes to exposed situations just below the summits. Old trees are resilient to high winds but younger saplings seem to require sheltered environments in order to establish. The species is an excellent interceptor of mist, with the leaf tips adapted to drip-tips which help to condense the mist. Dogwood also roots easily, allowing fallen trees to recover rapidly following landslips, etc. The species is functionally dioecious; male plants possess reduced stigmas and female plants possess reduced anthers, but in both cases the poorly developed sexual organs seldom if ever appear to be fertile. The flowering season is between late summer and early winter and pollination is by insects, mainly hoverflies (Percy and Cronk 1997). The seed can be dispersed via wind; however, it does not travel far from the parent plant.|
|Continuing decline in area, extent and/or quality of habitat:||Yes|
|Generation Length (years):||100|
|Major Threat(s):||Until the planted individuals reach sexual maturity the number of mature Dogwoods remains low and fragmented. The quality of the habitat at High Peak is deteriorating potentially threatening the Dogwoods growing there.|
The species is currently protected by the Endangered Species Ordinance; however, this is due to be superseded by the Environmental Protection Ordinance (currently in the final stages of drafting), which is due to be in place in 2016.
|Citation:||Ellick, S. & Lambdon, P.W. 2016. Nesohedyotis arborea. The IUCN Red List of Threatened Species 2016: e.T30378A67379194.Downloaded on 13 December 2017.|
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