|Scientific Name:||Aloe suzannae Decary|
|Red List Category & Criteria:||Endangered B2ab(i,ii,iii,v) ver 3.1|
|Reviewer(s):||Hilton-Taylor, C., Rabehevitra, D., Rabarison, H., Vololoniaina, J. & Letsara, R|
Aloe suzannae has a restricted geographic range. Recent surveys have confirmed the presence of this species at sites in Itampolo, Androka and Mangatsiaka Forest near Taolagnaro but other sites such as Ambovombe-Androy and Amboasary-Sud have been extinct for many years due to urbanization and conversion of the natural habitat into an industrial sisal plantation. The remaining subpopulations likely represent four threat-defined locations, which are separated by more than 20 km and contain between 10 – 300 individuals. The combination of small populations and poor dispersal (seeds are likely to be dispersed only short distances by the plant itself and wind) indicates the species is severely fragmented. The extent of occurrence (EOO) was estimated to be between 5,754 and 8,319 km2 and area of occupancy (AOO) was estimated to be between 24 and 934 km2. Both the EOO and AOO are estimated to be in continuing decline due to the conversion of the natural habitat into cropland. Many plants have been reported as burnt or cut for unknown reasons. There is occasional illegal collecting of plants from its natural habitat by local villagers which may also be causing a continuing decline in number of mature individuals. The species therefore qualifies for listing as Endangered.
|Previously published Red List assessments:|
Aloe suzannae is presently restricted to southern Madagascar in Ampanihy district (Itampolo, Ankazoabo and Androka) and Taolagnaro district (Andohahela and Ankodida). A. suzannae was previously known from Ambovombe-Androy and Amboasary-Sud but it is likely the species is now locally extinct in these areas. A. suzannae occurs in southwestern coastal bushland and dry spiny forest. The species occurs within three Protected Areas. The area of occupancy (AOO) was estimated to be 24 km2 by using a 2 x 2 km grid of all known extant localities. Two localities from the oldest collections were not included as the species is believed to be locally extinct in these areas based on a survey in 2011. The area of suitable habitat was used to infer a plausible maximum area of occupancy (AOO) value, which was calculated to be 934 km2. The extent of occurrence (EOO) was estimated to be 8,319 km2 calculated by using CAT (Moat 2007) based on the known extant localities. By excluding the oldest collection and by adding observations in Mangatsiaka forest east of Amboasary-Sud and at Andohahela National Park Parcel 3 (F. Rakotonasolo pers. 2008), an inferred maximum extent was calculated as 5,754 km2. The subpopulations contain 10 to 300 individuals and these are separated by distances of up to 20 km. The dispersal systems of the species are autochory and anemochory (Carter et al. 2005), therefore the seeds are not likely to be dispersed long distances. Due to geographic separation and the limited dispersal mechanism we estimate that there are four threat-defined locations.
|Range Map:||Click here to open the map viewer and explore range.|
Exact population size is not known but recent surveys between 2004 to 2013 show that it is likely there are less than 1,000 mature individuals. Further survey work is needed to calculate a more precise estimate of population size. The subpopulations are estimated to contain 10 to 300 individuals and these are separated by distances of up to 20 km. The seed of this species is wind dispersed and self-dispersed; therefore the seeds are not likely to be dispersed long distances.
|Current Population Trend:||Decreasing|
|Habitat and Ecology:||The species grows in southwestern coastal bush with Euphorbia stenocalda and invasive Opuntia sp. on sandy soil and limestone substrate (Spath 2013); also found in dry spiny forest with Alluaudia ascendens, A. dumosa and A. procera.|
|Continuing decline in area, extent and/or quality of habitat:||Yes|
|Use and Trade:||At the moment there is no documented evidence or reports about the collection of this plant in the wild for international commercial purposes, however, there is anecdotal evidence about the collection of young individuals (on a small scale) in their habitat in the region of Itampolo and Androka from fieldwork in that area in 2013. The collection was primarily for ornamental display in local villages. The species is included within CITES Appendix I.|
|Major Threat(s):||Based on our observations in the field and recent reports (Castillon and Castillon 2010, Spath 2013) the clearance of habitat for the expansion of crop land is the most significant threat to A. suzannae. It should also be noted that several specimens of A. suzannae have been found burnt or cut down for unknown reasons (Spath 2013). Further threats include domestic goats eating or trampling the seedlings and the collection of young plants in the wild by local villagers, although this is likely to be a minor threat.|
The species exists within three protected areas at Andohahela, Tsimanampetsotsa and Ankodida (WWF 2011). Seeds have been banked for ex situ conservation with seeds duplicated at the Silo National des Graines Forestières (SNGF), Madagascar and the Millennium Seed Bank, UK. Living collections grown from seeds collected for the Millennium Seed Bank Programme have been planted at the Tsimbazaza Botanic Garden, Madagascar. To protect the species in their natural habitat and to ensure the survival of existing population in the wild, mainly those outside of the protected areas, we recommend the development and implementation of a local conservation action plan which involves the local communities. Public awareness through various methods of communication including posters and leaflets should be developed at the remaining sites of occurrence about the importance and rarity of the species. Further research and investigation is needed to determine the exact population size and trends. The species is listed on CITES Appendix I.
|Citation:||Rakotoarisoa, S.E. 2016. Aloe suzannae. The IUCN Red List of Threatened Species 2016: e.T39057A67039967.Downloaded on 25 November 2017.|
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