|Scientific Name:||Acridocarpus monodii|
|Species Authority:||Arènes & P.Jaeger ex Birnbaum & J.Florence|
|Taxonomic Notes:||Acridocarpus monodii has been described by Boudet (1986) as the vicariant of A. chevalieri, with A. monodii occupying more arid climatic biotopes than A. chevalieri.|
|Red List Category & Criteria:||Endangered B1ab(iii)+2ab(iii) ver 3.1|
|Reviewer/s:||Hilton-Taylor, C. & Lutz, M.L.|
Acridocarpus monodii is a shrub known from only five herbarium collections from the Bandiagara cliff area in central Mali, with additional sightings and field records by Birnbaum in the same area in 2004. Collection years range from 1935 to 2006, with both the northernmost specimens having been collected in 1958. These sites were revisited in 2004 by Birnbaum and A. monodii was not found.
Minimum and maximum values have been calculated for both extent of occurrence (EOO) and area of occupancy (AOO), providing values for both eventualities, i.e. a) northern populations having been lost completely since 1958 and b) northern populations still existing, but just not found by Birnbaum. Minimum EOO and AOO values are 425 and 27 km² and maximum values are 2,444 and 45 km² respectively. Birnbaum (2007) has estimated the distribution range of this species at 20-30 km², which can be considered an approximation of the AOO for this species, excluding the northern populations. Altitude range decreases from 245-883 m to 400-550 m if the northern points are removed from analysis.
Assuming the northern population has definitely disappeared, an 84% decline in EOO and a 40% decline in AOO over the last 50 years (1958 to 2008) can be inferred from the above calculations. Although the above decline in EOO (causing a corresponding population size reduction) could possibly allow for a rating of “Critically Endangered” under criterion A (depending on establishing a suitable generation time), it is not considered appropriate for several reasons:
• A. monodii has been described as very abundant and even dominant in the areas where it grows.
• A. monodii does not appear to be threatened by general human disturbance
• The areas around Kikara and Djime have only been searched once for the species and therefore permanent loss from these areas cannot be confirmed
• All known populations are contained within the Cliffs of Bandiagara (Land of the Dogons) World Heritage Site, offering some protection
Both the minimum and maximum EOO and AOO values, however, allow for a rating of Endangered, combined with the facts that at present the species is known from a few locations only and a continuous decline in habitat and/or EOO is likely to occur due further interference of water sources for agricultural purposes and increased drought and desertification in the region. Acridocarpus monodii has been rated here as Endangered.
Acridocarpus monodii is endemic to the Dogon plateau in central Mali. It is found along the base of the escarpment “Falaise de Bandiagara” with the southernmost population being located near and in the village of Yabatalou. Although collections from near Douentza and Kikara (north of the escarpment) exist from 1958, no plants were found in these areas when re-visited by Birnbaum in 2004. On the other hand, the first collection of this species was in 1935 near/in the village of Sangha and Birnbaum has found A. monodii a few kilometres south west of Sangha in recent years. Maximum EOO and AOO were calculated using all known records and minimum EOO and AOO using only those along the southern part of the Bandiagara cliffs as confirmed by Birnbaum (2005).
The minimum EOO value is based on the ellipse drawn on a map, containing the area where the species was found by Birnbaum in 2004, and the maximum is calculated from the convex hull drawn around all known previous locations. The ellipse size drawn here agrees with the species’ 100 km perimeter and latitude range according to Birnbaum (2005). Minimum and maximum AOOs are based on three or five grid cells of 9 km², three for the southern population only and five for all known previous locations. 3 km² is considered an appropriate cell size for this species due to its extreme abundance in the localities where it is known to exist (e.g. Yabatalu).
|Range Map:||Click here to open the map viewer and explore range.|
Birnbaum (2005) found A. monodii in numerous localities between the latitudes 14°13’07” and 14°31’47”, along the base of the Bandiagara cliffs from the road linking Bankass and Somadougou to the village of Idielina. He describes the plant as abundant in the valleys and on the cliffs in this region, with the village of Yabatalu being without a doubt the area where this plant is the most frequent. Here it is the dominant species in some locations (so dominant that it appears to be an invasive, Birnbaum (2007)), being notably abundant where the scree meets the cliff face. Acridocarpus monodii is believed to flourish in Yabatalu due to the underground water supply which flows all year round and more specifically very close to where the species has proliferated. In this area the plant is entirely of the “bushy” (not cascading) form.
Jaeger and Winkoun (1962) described the species as “less frequent” at the bottom of the Kikara ravine, in comparison to the number of plants found on the boulders near Djimé. Due to not managing to relocate these populations in 2004, Birnbaum (2005) believes that the populations to the north of the cliffs sampled by Jaeger in 1958 are likely to have been wiped out by the severe droughts in 1973/74 and 1983/84. In addition, it has been suggested that the disappearance of the A. monodii (and the inhabitants) from Kikara village was caused by the interruption in the 1980s of the permanent water source that used to flow from the top of the Gandamia Cliff (Birnbaum, 2008).
|Habitat and Ecology:||
Acridocarpus monodii is a chasmophyte branching sarmentose shrub found in shady areas on cliff faces and scree, which are reasonably humid for at least some of the dry season. It displays two forms depending on the growing conditions, namely “bushy” lianescent in more shady forested habitats and cascading when on sharp inaccessible cliff faces. It flowers and fruits throughout the dry season, from September to May. Flowering and fruiting is asynchronous between plants and individuals can often be seen with young flowers and mature fruits on different branches. Maturing of the fruit is believed to bring about dormancy of the embryo, with Birnbaum (2004) having been unable to germinate mature seeds, even after scarification or soaking. On the contrary, seeds from immature fruits (pale yellow flesh) have been found to germinate without difficulty on a moist base. Acridicarpus chevalieri collected from the Manding Hills appears to share the same properties.
The Bandiagara plateau is comprised of sandstone, with rock slabs covered in holes, faults and caves that link together via springs along the base of the cliffs. The escarpment has been shaped into numerous irregularities, indentations, and promontories, and is pierced by thalweg ravines, gorges, and rocky passages connecting the plain and plateau (UNEP-WCMC 1995). At low levels the ravines are blocked by immense detached blocks of rock and thalwegs support a humid and shaded microclimate with dense vegetation. Water is also retained in rock fissures, resulting in seasonally boggy areas on horizontal or gently sloping rock strata. The Bandiagara cliff and ravine vegetation is in patches very diverse and dense; the chasmophytic flora includes Cissus quadrangularis, Ficus lecardii, Boscia angustifolia, Euphorbia sudanica, Lannea microcarpa and Combretum lecardii (Jaeger and Winkoun 1962). Average rainfall for 1994 was 600 mm, with 849.4 mm falling in 59 days at Bandiagara and 715.4 mm in 54 days at Sangha. Droughts last for up to eight months of the year. Rain falls irregularly mainly from June to September. Shade temperatures in May are reported to be some of the highest in the Sahel region (Pern 1985).
Acridocarpus monodii populations are found at the border between two ecoregions, namely the West Sudanian Savanna and Sahelian Acacia Savanna. GLCC 2000 data suggests the species is found in two main habitats, namely “Herbaceous Cover, closed-open” and “Cultivated and managed areas”.
The greatest threats to the area and A. monodii in particular, include drought and desertification. Birnbaum (2005) has suggested that the northern populations of A. monodii may have been wiped out by the severe droughts of 1973-74 and 1983-84, with this region being at the most risk of desiccation due to the strong “Harmattan” wind blowing from the northeast.
Human activities have reduced, degraded, and fragmented both the West Sudanian Savanna and Sahelian Acacia Savanna ecoregions, where this species is found. The savanna vegetation has been profoundly degraded by fire and scrub clearance, most notably in the vicinity of village communities (Jaeger and Winkoun 1962). However, due to the inaccessibility of many of the areas where A. monodii grows, these processes are unlikely to threaten the species. Furthermore, the abundance of this species around and in the village of Yabatalu suggests that A. monodii is not seriously threatened by general anthropogenic pressures, which have played a very important role in shaping the Dogon landscape over the last few thousand years. Damming of water sources for agricultural purposes however is likely to be a significant threat to A. monodii populations. The creation of these small “dams” have been know to dry out valleys, including that near Kikara in the 1980s.
The entire confirmed extent of A. monodii is contained within the Cliffs of Bandiagara (Land of the Dogons) World Heritage Site which was established in 1989. The government is conserving the site because of its exceptional architectural structures and the interaction between man and the natural environment. One of the key management aims is the maintenance of the Dogon culture and associated houses, granaries, ritual sanctuaries and "toguna". Also of importance are the surrounding natural features and landscape and a fauna and flora survey is currently being undertaken on behalf of the "cantonnements forestiers" (Diakite 1988). However, insufficient funding means that the site is inadequately patrolled (UNEP-WCMC 1995).
The importance of protecting species such as A. monodii was highlighted during a GEO expedition to the Bandiagara cliffs and escarpment, when discussions between scientists, experts on traditional knowledge and local communities were held (GTZ-GEO 2005). Acridocarpus monodii is on the target species list for the Millennium Seed Bank Project and was included in the Mali Collection Guide compiled by the Species Targeting Team. Seed for banking (in Mali and the UK), however, has not been collected as yet as plants found in the October 2006 collecting trip where not fruiting. Plans are to collect seed in March/April 2008.
|Citation:||Crook, V. 2011. Acridocarpus monodii. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 11 March 2014.|
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