Aloe belitsakensis Rakotoarisoa, 2017

Rakotoarisoa, Solofo E. & Grace, Olwen M., 2017, Aloe belitsakensis (Asphodelaceae): a new species from north-western Madagascar, Phytotaxa 328 (3), pp. 276-282 : 277-281

Aloe belitsakensis Rakotoarisoa , sp. nov.

Acaulescent plant, inflorescence simple, erect, raceme densely capitate. Differs from related species of the Aloe capitata group by the length of its inflorescence, which can reach 2 m, and by the character of its inflorescence that is simple, erect and straight.

Type:— MADAGASCAR. Belitsaka: Province of Mahajanga, Melaky region , dry shrubland on white sand, ca. 52 km SW of Morafenobe, elevation ca. 225 m. Cultivated and flowered in private garden in Antananarivo, 10 Oct 2015, S. E. Rakotoarisoa RSE 847 (holotype TAN!; isotype K!) .

Description:— Plant acaulescent, solitary or suckering to form small clumps. Leaves ca. 20–25, densely rosulate, erect to slightly curving inward, lanceolate-acuminate, 6.5–8.5 × 37–45 cm, slightly canaliculate, green tinged reddish; margin armed with strong yellow deltoid teeth, 3 × 4–5 mm, 15 mm apart. Inflorescence 2–4, erect, simple, rarely with one branch, 0.70–1.15(–2.0) m. Peduncle 2.5 cm in diameter at base, with 9–18 sterile triangular bracts, scarious, 8 × 15 mm, with numerous brown striations. Raceme terminal, capitate ( Fig. 2B ), 10 × 11 cm, densely flowered. Floral bracts 4 × 3 mm, papery. Petiole 35–38 mm, reddish orange. Perianth orange-yellow, 20–22 mm, 5 mm across ovary, narrowly campanulate ( Fig. 2C ); inner and outer tepals free to the base; stamens yellow-orangey, exserted for 10–13 mm; style yellow-orangey, exserted 8 mm.

Flowering time:—October

Fruit:— November–December

Etymology:— It is named after Belitsaka village in the area where the species is found.

Affinities and diagnostic characters:— The affinity of Aloe belitsakensis to the A. capitata group is evident at a glance, given the densely flowered, capitate raceme ( Fig. 2B ). Flowers closely resemble those of a subspecies or variety of A. capitata with one notable exception: the length of the pedicel, which is significantly longer in A. belitsakensis (35–38 mm vs. 25–30 mm). Leaves of the new species are reminiscent of A. ericetorum , but the latter are much smaller (23–49 cm vs. 19 cm). However, its uniqueness lies in the branching and stature of the inflorescence. Aloes with a capitate inflorescence are generally characterised by inflorescences that are branched at least twice, even exceeding four-branched in the case of A. capitata and infraspecific ranks of this species. In A. belitsakensis , however, the inflorescence is always erect, simple or, rarely, single branched. Furthermore, the inflorescence can reach 2 m in height, which is never observed in other members of the Aloe group with capitate racemes where inflorescences are typically less than 1 m tall. Aloe trachyticola is the only other member of the A. capitata group with a single, erect and simple (rarely branched) inflorescence ( Fig. 3 ). However, the inflorescence of A. belitsakensis is longer (2 m vs. 0.9 m) and bears distinctly orange-yellowish flowers, whereas the flowers are red in A. trachyticola .

On the leaves, the marginal teeth are yellow in A. belitsakensis , whereas they are brown or dark red in all varieties and subspecies of A. capitata ( Fig. 4 ). Leaves are always erect and canaliculate for this new species, yet for most varieties of A. capitata the leaves are almost flat, and only the young leaves are erect.

Conservation status:— This species is not common in the area. It is found only in dry shrubland on white sandy soil, a habitat restricted to the western side of the Tsingy de Bemaraha National Park. Beyond the boundary of the Protected Area, the habitat is under permanent human pressures, such as bush fires, illegal collecting and logging. The Extent of Occurrence (EOO) of the species is estimated to be 469 km 2 based on the suitable habitat of the species. For these reasons, the new species is assigned the category of Endangered (EN) according to the IUCN Red List criteria ( IUCN 2001).

Figures

FIGURE 2. Aloe belitsakensis Rakotoarisoa sp. nov. growing in a private garden in Antananarivo, photographed in October 2015. A. General habit of adult plant with inflorescence 1.1 m high. B. Raceme showing open flower. C. Flower opening sequence from the top to the base of the same raceme. Photographs: S.E. Rakotoarisoa.

FIGURE 3. Aloe trachyticola in habitat at Ibity Massif (Central Plateau) in May 2004. Photograph: S.E. Rakotoarisoa

FIGURE 4. Aloe capitata in habitat at Itremo (Central Plateau) in July 2007. Photograph: S.E. Rakotoarisoa