|Scientific Name:||Rothmannia annae|
|Species Authority:||(E.P.Wright) Keay|
Gardenia annae E.P.Wright
|Red List Category & Criteria:||Critically Endangered B1ab(iii,v)+2ab(iii,v) ver 3.1|
|Assessor/s:||Ismail, S., Huber, M.J. & Mougal, J.|
|Reviewer/s:||Gibbs, D. & Lutz, M.L.|
Rothmannia annae's natural occurrence is nowadays restricted to Aride Island with a total area of only 0.7 km² (maximum extent of occurrence (EOO) and area of occupancy (AOO)), the only remaining location. A continuing decline in mature individuals has been observed. The causes that led to the extinction of this species on Mahé, Silhouette, Praslin and Félicité are not fully understood. It is possible that introduced insect pests caused the rapid extinction. A similar event could drive the remaining population on Aride Island to extinction.This species is listed as Critically Endangered.
|Range Description:||Endemic to Seychelles, this species is now restricted to Aride Island with a total area of only 0.7 km² (Robertson 1989, Friedmann 1994). It used to occur on Mahé (Horne 1874 in Baker 1877, Schimper 1899 in Diels 1922 and Thomasset 1905 in Summerhayes 1931), Silhouette (Gardiner 1905), Praslin (Horne 1871) and Félicité (Wright 1867 and Horne 1871). The EOO and AOO are less than 100 km² and 10 km² respectively.
This species has recently been introduced to Frégate Island (Hill 2002). These individuals are performing well and are also regenerating spontaneously (K. Beaver pers. comm. 2007). It is unlikely that these individuals can be regarded as naturalized. As there is no evidence that these individuals form a self-sustaining subpopulation these individuals cannot be incorporated in this assessment.
Native:Seychelles (Seychelles (main island group))
|Range Map:||Click here to open the map viewer and explore range.|
The only remaining population consists of fewer than 2,500 mature individuals. In 1999, 987 mature individuals were counted on Aride Island (J. Bowler and J. Hunter pers. comm. 1999). A continuing decline in the number of mature individuals can be observed (Carty 2006). A population decline in the past is given as this species has disappeared from Mahé, Silhouette, Praslin and Félicité and is now confined to Aride Island.
A partial census was carried out by Harriet and Sam Carty during December 2005 and early January 2006. The areas covered represent the most important stands of R. annae. In the same area 736 adult plants were counted in 1996. In 1999, 645 adult plants were counted (representing two thirds of the total population in 1999). In 2005, 628 adult plants were counted. This gives a downward trend over nine years in the surveyed area (Carty 2006). It is not sure if this survey is representative for this species, as the surveyed areas were not chosen at random. But this survey indicates an approximate reduction of 15% over the last nine years, for approximately two thirds of the population. This is a dramatic reduction as the generation length exceeds 30 years.
An exact quantification of the historical decline based on the extinctions on several islands and on the observed ongoing decline over three generations is not possible. The entire area of the islands where the species has gone extinct is 218.8 km². Compared with the 0.7 km² of Aride Island this indicates a massive decline in the past 100 years. Therefore it can be suspected that the past range decline exceeds 50% in the past 100 years, even a decline of 80% is plausible. Reasons for this past and present population decline are not exactly known. It is possible that introduced insect pests caused the rapid extinction on the islands.
|Habitat and Ecology:||Grows among boulders and in forest at lower altitudes. The natural population is isolated on one small island.|
The restricted range is the main threat to this species. The exact reasons for the ongoing observed population reduction are not known. The most plausible reasons are intrinsic factors and also competition with Pisonia grandis.
Because the extinction reasons on the other islands are not surely known, the same event could happen also on Aride Island. It is possible that introduced insect pests caused the rapid extinction on some of the islands (Friedmann 1994).
|Conservation Actions:||Confined to Aride Strict Nature Reserve.|
|Citation:||Ismail, S., Huber, M.J. & Mougal, J. 2011. Rothmannia annae. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. <www.iucnredlist.org>. Downloaded on 22 May 2013.|
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