Critically Endangered species

Wahlenbergia tibestica (Campanulaceae)

Wahlenbergia tibestica is an annual or hydrophyte found in seasonal or intermittent freshwater lakes, marshes and pools. This species has been collected only once, in Tibesti (Chad). Its ecology is not clear, but the plant is considered endemic to the region. It has an Area of Occupancy (AOO) of 4 km². In view of the severe climate in the north of Chad,

particularly for an aquatic plant, we project a continuing decline of the area, extent and/or quality of habitat.

Bolboschoenus grandispicus (Cyperaceae)

Bolboschoenus grandispicus has only been reported from Senegal, Guinea-Bissau and Cabo Verde. However, it is now considered restricted to Senegal. This species is found at the edge of swamps in freshwater depressions behind the coastal dunes. The species is assessed as Critically Endangered based on a restricted AOO of 4 km² and occurrence at one location, based on the threat of habitat degradation, which is resulting in a continuing decline in habitat. The only recently confirmed and currently extant subpopulation is near Dakar (Rufisque), which was found in 2014 (A. Mesterházy pers. obs. 2014).

Elatine fauquei (Elatinaceae)

The plant is known only from the type locality, the Ravin Balassogo (Balasoko) in Mali, in or around a fountain (spring) in a stony valley. Its AOO is very low at 4 km² and it occurs in one location based on the threat from recreational activities.

Because this type of habitat is very fragile, we infer a continuing decline in the area of occupancy and area, extent and/or quality of habitat.

Eriocaulon adamesii (Eriocaulaceae)

Eriocaulon adamesii (CR (Possibly Extinct)) is a rare endemic in West Africa, known from few collections from Sierra Leone Figure 7.3 Dopatrium senegalense is a widespread species with no known major threats, assessed as Least Concern. This species colonises wet places such as rice paddies. This plant in Senegal is in full flower. © Attila Mesterházy

(Hepper, 2000) and one from Liberia, collected mainly in the 1960s. Recently, none of these collections have been reconfirmed. However, some potential sites need surveying for this species because there are still some remaining natural habitats which can be found near type locality. The most significant threat is habitat degradation as a consequence of increasing human activity, such as the building of houses, farms and plantations, and this has resulted in a continuing decline in habitat extent and quality. If extant, the species is expected to have an AOO of, at most, 8 km².

Eriocaulon obtriangulare (Eriocaulaceae)

Eriocaulon obtriangulare (CR (Possibly Extinct)) has only been collected once from Côte d’Ivoire in 1967. Although the type locality is in Comoé National Park, where the influence of human activities is low, this species has not been found since the initial collection. The type locality was visited in 2013, but this species was not found (A. Mesterházy pers. obs. 2013).

As the site is in the north forest-savanna region, dry periods might become longer in the future with lower annual rainfall due to climate change, which might cause a negative effect to temporary pools. As this species has not been found since 1967, but suitable habitats remain at Comoé National Park where the species might appear in the future, it is assessed as Critically Endangered (Possibly Extinct). Further surveys are needed to look for this species in Comoé National Park.

The type specimens are all incomplete and so the taxonomic status of this species is not clear, and further research is recommended.

Inversodicraea abbayesii (Podostemaceae)

Inversodicraea abbayesii (CR (Possibly Extinct)) was previously assessed as Ledermaniella abbayesii (DD) in 2008 (Diop, 2010). Since that time, the species has been transferred to the genus Inversodicraea (Cheek et al., 2017), and a targeted survey for Podostemaceae including this species was made in January 2018 resulting in new data allowing a revised assessment (Cheek & Diop, 2018).

Inversodicrea abbayesii is endemic to Guinea, collected by Des Abbayes c. 1950, and known only from the single collection that he made at that time from the Grandess Chute de Kinkon, near Pita in the Fouta Djalon Highlands. Des Abbayes observed that it emerged to flower from the white water of the falls themselves. In January 2018, a team from the National Herbarium of Guinea with RBG Kew (funded by a Darwin Initiative project on Guinea Important Plant Areas), with expertise in Podostemaceae, visited the falls at the best season to rediscover this species (Couch et al., 2019). They found the species to be absent, probably because a hydro-electric dam constructed after the species was collected, has diverted much of the river flow around the falls, and has probably altered the natural hydrological pattern. In addition the river supplying the falls carries large amounts of silt (deposited on the rocks of the bank) and is contaminated

on its journey through the town of Pita where it is used for laundry and other purposes. Although locally extinct at the type locality, the species may yet be found at other sites, since several falls in Guinea have never been sampled for their plants. However, many species of this family are single-site endemics so it cannot be ruled out that this species is globally extinct. The species is therefore assessed as Critically Endangered (Possibly Extinct) (Cheek & Diop, 2018).

Inversodicraea pygmaea (Podostemaceae)

Inversodicraea pygmaea (CR (Possibly Extinct)) is only known from a single locality: the Grandes Chutes de Kindia waterfalls in Guinea. In January 2018, a team of four from the National Herbarium of Guinea with RBG Kew with expertise in Podostemaceae, visited the falls at the best season specifically to rediscover this species (Cheek, 2018). They found this species and all other Podostemaceae species to be absent, including even the most widespread, common and ecologically tolerant, Tristicha trifaria. A hydro-electric dam constructed in 1962 after the species was discovered, has diverted much of the river flow around the falls, and has altered the natural hydrological pattern. In addition, the stream below the dam is contaminated where it is used for laundry and as a latrine, explaining high algal growth, inimical to Podostemaceae, which are associated with clean, nutrient poor water.

Stonesia fascicularis (Podostemaceae)

Stonesia fascicularis (CR (Possibly Extinct)) is known only from the type locality, Grandes Chute de Kinkon, near Pita in the Fouta Djalon Highlands, c. 1950 (Cheek & Ouedraogo, 2018a), as per I. abbayesii (Cheek & Diop, 2018).

Stonesia gracilis (Podostemaceae)

Previously assessed as DD by (Ouedraogo, 2010) on the basis of sparse and erroneous information, the assessment of Stonesia gracilis was updated and revised to CR (Possibly Extinct) in 2018 by Cheek and Ouedraogo (2018b). This species, together with Inversodicraea pygmaea, is only known from the Grandes Chutes, Kindia but was recently found to be absent from the site ( Cheek and Ouedraogo, 2018b). There appears to be no evidence for records of this species in Cameroon and Sierra Leone, although occurrence in the latter is possible.

7.2.2 Endangered species

Commelina ascendens (Commelinaceae)

This plant, known from Nigeria and Ghana, is a herb found in secondary or open primary forests, often by rivers. It has an AOO of 60 km² and is threatened by severe drought, which is exacerbated by climate change. A continuing decline in its AOO and the quality of its habitat is inferred.

Cyperus lateriticus (Cyperaceae)

This species was known from only the type specimen collected in 1953. However, it has recently been recorded both at the type locality (near Tambacounda) and at one other location (near Kédougou) (A. Mesterhazy pers. obs.).

The most significant threat is habitat degradation as a consequence of increasing human activities (e.g. agriculture and urban expansion), and the increased occurrence of droughts decreasing habitat quality and increasing frequency and impact of bush fires during the dry season.

The area in which this species is known to occur (the Kédougou and Tambacounda regions of Senegal) is impacted by mining (in particular artisanal gold mining). It is not recorded from any protected areas, though it could be present in Niokolo-Koba National Park since this protected area is located near the two known locations in Senegal.

More research is needed to confirm whether this species is endemic to Senegal, or whether it also occurs across the border in Guinea, as well as to assess the population trends and study the threats posed to this species.

Aldrovanda vesiculosa (Droseraceae)

The Waterwheel Aldrovanda vesiculosa (EN) is a carnivorous, perennial, free-floating, rootless aquatic herbaceous plant known from 379 natural historical collections from 43 countries (Cross and Adamec 2020). However, this species has declined over the last century to only 50 confirmed extant localities. Two thirds of these are found in one region in Poland and the Ukraine, with the remaining 18 sites thinly spread across four continents. In western Africa, historic localities are known from Togo, Ghana, Chad and Cameroon, but none of these have been recently confirmed.

In Cameroon, the species has previously been recorded from the shores of Lake Fianga near the border with Chad in the Extreme North region (unverified since 1963), and from the vicinity of Lake Bamendjing on the border between the rugged and mountainous West and Northwest regions (unverified since 1974). In Chad, the species was known from four sites near Sarh, formerly Fort Archambault, in the Chari River delta, between 1962 and 1968. With A. vesiculosa known from Lake Fianga’s northern reaches in Cameroon, it is possible that the species’ occurrence extends across the border into swampy areas fringing the lake in southwest Chad. In Ghana, the species was known from swampland near Kete Krachi, in the northern reaches of the expansive Lake Volta, and in swamps of the Volta River delta, east of Dabala, in the Keta Lagoon protected area unverified since 1963. A second ambiguous location is in Lake Volta. As the wetlands surrounding this immense lake are numerous, it is possible that a number of populations may exist in the region (unverified since 1965). In Togo, the species was known from the Koumongou River, near the town of Sansanné-Mango in the northeast (unverified since 1984).

Aldrovanda vesiculosa is not protected by legislation in any African nation, and is not included in any regional conservation initiatives.

Najas hagerupii (Hydrocharitaceae)

Najas hagerupii (EN) has been collected in one locality in each of Cameroon, Ghana and Mali. These represent three locations based on the threat of climate change and severe weather. The AOO is 16 km². This species occurs in temporary and permanent marshes and pools, in both shallow and deep waters. Threats include human intrusions and disturbance, especially recreational activities, natural system modifications, invasive of non-native species, and climate change and severe weather, characterised by droughts and temperature extremes.

Pandanus senegalensis (Pandanaceae)

This species is a small tree that grows along rivers and waterfalls in a small area of southeastern Senegal, Mali and Burkina Faso. This species occurs in a specific habitat of gallery forest and there is likely increasing pressure on this type of vegetation for housing, urbanisation and smallholder agriculture from an increasing human population over its distribution area. While one specimen (the type) is from in or near a protected area, the Niokolo-Koba National Park in Senegal, it is unclear if the site is actually in the protected area, and the tree has not been re-collected there since 1960 (Beentje, 2020).

7.2.3 Vulnerable species

Aneilema mortonii (Commelinaceae)

This species is endemic to western Africa where it is recorded in Ghana and Togo. This species occurs in open grassland, scrambling among grasses beside ponds, on marshy ground and in savanna, and is potentially impacted by pollution from agricultural development, invasive species and drought. The species’ low AOO of 48 km² is thought to be an underestimate based on low collecting effort.

Blyxa senegalensis (Hydrocharitaceae)

Ths species is a hydrophytic herb of temporary pools in lateritic outcrops. The plant is recorded from 20 herbarium specimens from six countries; Senegal, Gambia, Guinea-Bissau, Guinea, Mali and Sierra Leone. Despite its widespread distribution, it has a restricted area of occupancy (AOO) of 28–500 km². This species is thought to be endemic to the western part of western Africa, where it is potentially impacted by agricultural development, invasive species and drought, all of which are leading to continuing declines in habitat quality and extent.

Rhytachne furtiva (Poaceae)

This perennial species grows in savanna, mostly on disturbed

Figure 7.4 Blyxa senegalensis is an uncommon species confined to western Africa, where it can be found in temporary pools. This specimen was recorded in Senegal. © Attila Mesterházy

secondary sites, but also in marshy savanna on floodplains.

It can also be found around the edges of small pools on clay soil. It is known only from southeast Burkina Faso and west Ghana from six locations. These locations are threatened by an increasing frequency of fire and drought, which are leading to continuing declines in its habitat extent.