Borassus akeassii Bayton, Ouédr. & Guinko, Bot. J. Linn. Soc. 150: 420 (2006)

Primary tabs

http://media.e-taxonomy.eu/palmae/photos/palm_tc_346107_4.jpg

Distribution

Map uses TDWG level 3 distributions (http://www.nhm.ac.uk/hosted_sites/tdwg/geogrphy.html)
Beninpresent (World Checklist of Arecaceae)B
Burkinapresent (World Checklist of Arecaceae)B
Central African Republicpresent (World Checklist of Arecaceae)B
Guinea-Bissaupresent (World Checklist of Arecaceae)B
Ivory Coastpresent (World Checklist of Arecaceae)B
Nigerpresent (World Checklist of Arecaceae)B
Nigeriapresent (World Checklist of Arecaceae)B
Senegalpresent (World Checklist of Arecaceae)B
Zairepresent (World Checklist of Arecaceae)B
Restricted to West and Central Africa. Aké Assi and Guinko (1996) report that the palm is present in Benin, Burkina Faso, Côte d’Ivoire, Mali, Niger and Nigeria. Borassus akeassii (as Borassus sp. aff. flabellifer) has also been recorded in Senegal and the Central African Republic (Arbonnier 2002). However, the range of B. akeassii may be much wider than suggested due to misidentification of the palm as B. aethiopum. Johnson (1984) noted that Borassus aethiopum in Guinea-Bissau was used for wine production. He also noted that the palms have green, orange-sized fruits and both these facts suggest B. akeassii. This study can confirm the presence of B. akeassii in Burkina Faso and Senegal only. In addition, a specimen collected in southeastern Congo-Kinshasa (Liben 2822) has been identified as B. akeassii. The identification was based on the distinctive commissural veins (Bayton et al. 2006); however, the specimen included no fertile material. (R.P. Bayton, A revision of Borassus L. (Arecaceae). 2007)A

Discussion

  • Initial examination of B. akeassii suggests a close relationship with B. flabellifer, as suggested by previous authors (Aké Assi & Guinko 1996; Ouédraogo et al. 2002). The similarities are largely a matter of scale, as B. akeassii is considerably smaller than other African Borassus species. This has been attributed to the intensive extraction of sap leading to reduced growth (Portères 1964). The small leaves, petiole spines, inflorescences and fruits are reminiscent of those of B. flabellifer. However, B. akeassii has a ventricose stem and that character is restricted to African Borassus. The rate of occurrence of branched pistillate inflorescences is much higher in B. akeassii than in any other species. Branching may occur in the rachis towards the base of the inflorescence, or in the flower-bearing rachillae. This may also be an artefact of husbandry as wine tapping damages the apical bud. Further investigation has revealed a number of characters that are unique to this species and probably independent of husbandry. The pollen is particularly distinctive; the gemmae are denser and almost completely obscure the tectum whereas it is clearly visible in the pollen of all other Borassus species. In the few areas where the tectum can be seen, it is reticulate rather than perforate. The commissural veins in the leaves are spaced further apart than in any species except B. heineanus. This character can be used to identify sterile herbarium material of B. akeassii. As the leaf desiccates, the lamina collapses onto the network of veins; in the leaves of B. flabellifer and B. aethiopum the commissures are close together and support the lamina, resulting in a smooth surface. In B. akeassii, the commissures are widely-spaced so the lamina sinks into the rectangular pits formed by the veins resulting in a puckered appearance (Bayton et al. 2006). The fruits are yellow-green with a pointed apex, thus resembling those of B. madagascariensis, but they are considerably smaller. These characters should ensure that living specimens can be identified to species, whether they have been tapped or not. It is conceivable that B. aethiopum var. domesticus could represent B. akeassii, as the fruits are described by Chevalier as small, globose, and yellowish-green in colour. His choice of epithet reflects the importance of this variety to local people (Chevalier & Dubois 1938), which is mirrored by B. akeassii. However, the type of var. domesticus consists of pyrenes only, and these cannot be identified with certainty. The presence of a second species in West Africa could cause some nomenclatural difficulties as the type of B. aethiopum is lost and was originally collected in West Africa. However, modern material collected from the type locality of B. aethiopum can be identified as that species. (R.P. Bayton, A revision of Borassus L. (Arecaceae). 2007)A

Biology And Ecology

  • Sudan savannas with 800 – 1100 mm annual rainfall. In Burkina Faso, most populations are semimanaged for wine production. Seed is collected and planted and the palms often have crops planted beneath (usually cotton or cassava). (R.P. Bayton, A revision of Borassus L. (Arecaceae). 2007)A

Conservation

  • Data deficient. Borassus akeassii may have a much wider distribution than is currently known. However, in the areas where it is known to occur, it is abundant and a significant crop for local people. Sambou et al. (2002; 1992) report that overexploitation is threatening populations of B. aethiopum in Guinea and Senegal, but it is possible that these refer to B. akeassii. In many cases, it is difficult to determine whether populations of B. akeassii are cultivated (i.e. planted) or merely wild plants that are exploited. (R.P. Bayton, A revision of Borassus L. (Arecaceae). 2007)A

Common Name

  • Burkill (1997) lists a huge number of indigenous names for Borassus (ostensibly B. aethiopum) in West Africa and many of these may be applicable to B. akeassii. The French name rônier (derived from the Wolof word rôn) is widely used in Francophone Africa for both Borassus species. (R.P. Bayton, A revision of Borassus L. (Arecaceae). 2007)A

Etymology

  • Borassus akeassii honours Professor Laurent Aké Assi (Abidjan University, Côte d’Ivoire) who, together with Professor Sita Guinko (University of Ouagadougou, Burkina Faso) first distinguished the palm from B. aethiopum (Aké Assi & Guinko 1996). (R.P. Bayton, A revision of Borassus L. (Arecaceae). 2007)A

Uses

  • In Burkina Faso, the main use for the palms is wine production, whereby the terminal bud is tapped to produce a sugary solution that is allowed to ferment. The undeveloped endosperm is also consumed, and the leaves are used for thatch and weaving. (R.P. Bayton, A revision of Borassus L. (Arecaceae). 2007)A

Description

  • Stem to 15 m tall, almost always ventricose, to 80 cm diam., when stem marked by numerous irregular scars, this is caused by tapping. Leaves glaucous, 8 – 22 in the crown; petiole and sheath 90 – 160 cm long; petiole 3.0 – 7.4 cm wide at midpoint, green, margins with small serrate black teeth (0.2 – 0.6 cm long), or teeth largely absent; costa 22 – 28 cm long; adaxial hastula conspicuous, to 2.4 cm, abaxial hastula rudimentary; lamina rather flat, radius to 160 cm maximum, dense indumentum on the ribs of some immature leaves; leaflets 45 – 82, 2.8 – 7.3 cm wide, apices acute and entire or splitting longitudinally with age, shortest leaflet 58 – 147 cm long, leaf divided to 60 – 99 cm; commissural veins 5 – 7 per cm, leaf anatomy isolateral. Staminate inflorescences branched to two orders, upper subtending branches terminating in 1 – 3 rachillae; rachillae green-brown and catkin-like, 23 – 36 cm long, 2.3 – 2.5 cm diameter, usually with a mamilliform apex; rachilla bracts forming pits that contain a cincinnus of 5 – 10 staminate flowers. Pistillate inflorescences spicate or branched to one order; rachis ± 80 cm long, flower-bearing portion 24 – 39 cm long with ± 23 flowers arranged spirally. Staminate flowers 0.4 – 0.6 cm long, exserted from the pits individually or in groups of 3 – 5; bracteoles 0.8 × 0.5 cm; calyx 0.5 × 0.2 cm, shallowly divided into three sepals, petal lobes 0.2 × 0.1 cm; stamens 6 with very short filaments, 0.1 × 0.03 cm, anthers, 0.1 × 0.05 cm; pistillode minute. Pollen monosulcate, elliptical, 51 – 72 μm long, aperture 47 – 61 μm long, polar axis 49 – 61 μm long; tectum reticulate, densely covered with supratectal gemmae. Pistillate flowers 3.5 × 3 cm, bracteoles 2 cm diam., sepals 2 × 2 cm, petals 1.5 × 1.5 cm. Fruits large, ± 15 cm long and ± 12 cm diameter, ovoid with a somewhat pointed apex, fragrant and yellowish green at maturity, produced inside persistent perianth segments; pyrenes 1 – 3, 6.8 – 9.3 cm × 5.4 – 7.5 cm. (R.P. Bayton, A revision of Borassus L. (Arecaceae). 2007)A

Materials Examined

  • BURKINA FASO. Comoé Prov.: Banfora Dept., 1 km W of Siniana village, 20 Jan. 2004 (♂), Bayton et al., 68 (AAU!, K!, OUA!); 500 m N of Lake Tengrela, 22 Jan. 2004, Bayton et al., 72 (K!, OUA!); 3 km N of Banfora, 22 Jan. 2004 (♀ & ♂), Bayton et al., 73, 74 (AAU!, K!, OUA!); Wolonkoto village, 29 July 1998, Ouédraogo & Boussim 9 (OUA!); Houet Prov.: Bobo-Dioulasso Dept., Dinderesso village, 28 July 1998, Ouédraogo & Boussim 8 (OUA!); Kadiogo Prov.: Somgandé, 18 June 1998, Ouédraogo & Guinko 2, 3 (OUA!); Ouagadougou city centre, 4 July 1998, Ouédraogo 4 (OUA!); Ouagadougou Forest, 5 July 1998, Ouédraogo 5 (OUA!). CONGO-KINSHASA. Kasai-Occidental Prov.: Kamulolo, without date, Liben 2822 (K!). SENEGAL. Senegambie, 1840, Brunner s.n. (K!); Kaolack Region: Kaolack, 1906, Chevalier s.n. (P!); Louga Region: Linguere Dept., Velingara in Ferlo, 30 Oct. 1989 (♂), Lawesson 5444 (AAU!); Thiès Region: Mbour Dept., Ndianda village near Joal, 7 Dec. 1997 (♀ & ♂), Ervik & Sambou 307 – 309 (AAU!). (R.P. Bayton, A revision of Borassus L. (Arecaceae). 2007)A