Sunday, June 16, 2019

[Botany • 2019] Gladiolus mariae (Iridaceae) • A New Species from Fire-free Shrubland in the Kounounkan Massif, Guinea

Gladiolus mariae Burgt

in van der Burgt, Konomou, Haba & Magassouba, 2019.

Gladiolus mariae Burgt (Iridaceae), a new species from Guinea, West Africa, is described and illustrated. The new species is placed in Gladiolus sect. Decorati Goldblatt and compared with the nine species already known from that section. Flowering plants stand 28–160 cm high with 1–6 bright orange flowers, opening one at a time. The ecology of the new species is discussed in detail, and a description of the vegetation in the region is provided. Gladiolus mariae is at present known only from two uninhabited sandstone table mountains in the Kounounkan Massif, Forécariah Prefecture. About 210 plants were found, on rocky soils at altitudes of 650–1100 m. The majority of plants, about 160, were found in fire-free shrubland, in five patches of 1–4 ha each, dominated by fire-sensitive plant species, but grasses are infrequent. Gladiolus mariae seems vulnerable to grassland fires. The area of occupancy is 28 km2. The species is assessed to the IUCN category Endangered.

 Fig. 2. Gladiolus mariae – A: flowering plant; B: detail of leaf; C: base of plant showing corm and 3 cataphylls; D: upper part of plant with an open flower and a flower bud; E: upper part of fruiting plant with 5 mature fruits; F: mature, open fruit with seeds; G: detail of dotted epidermis of fruit; H: seeds. – Origin: A–D from Burgt & Haba 2012 (type gathering); E–H from Burgt 2161. – Drawing by Lucy T. Smith.

Fig. 1. Gladiolus mariae – A: habit of flowering plant; B: flowers; C: fruiting plant; D: fruit. – Origin: A from Burgt & Haba 2012 (type gathering); B from Burgt 2207; C, D from Burgt 2161. – All photographs by Xander van der Burgt. 

Gladiolus mariae Burgt, sp. nov.  

Holotype: Guinea, Forécariah Prefecture, southern plateau of Kounounkan Massif, ..., fl., 25 Sep 2016, X. M. van der Burgt & P. M. Haba 2012 (K001243991; isotypes: HNG, P, PRE, WAG).

Diagnosis — Gladiolus mariae morphologically resembles G. sudanicus Goldblatt. Gladiolus mariae plants are 28–160 cm tall with 7–11 foliage leaves and 1–6 flowers (vs 15–20 cm tall with 4 or 5 leaves and 2 or 3 flowers in G. sudanicus). The outer bract of the flower is 40–110 mm long (vs 20–25 mm long in G. sudanicus). The perianth tube is 39–50 mm long (vs 16–20 mm long in G. sudanicus); the tepals are 28–36 mm long and bright orange (vs 16–24 mm long and pale to deep pink in G. sudanicus).

Distribution — Gladiolus mariae is at present known only from two uninhabited sandstone table mountains in the Kounounkan Massif in Forécariah Prefecture, Guinea (Fig. 3). Sandstone plateaus elsewhere in the region are inhabited by farmers and cattle herders, and most of the original vegetation there has been modified by fire. If the species originally occurred elsewhere in the sandstone plateaus region, then it may still survive there, in rock crevices on vertical sandstone cliffs.

Habitat and ecology — Gladiolus mariae occurs on sandstone, on rocky soils; altitude 650–1100 m, in three vegetation types. Most plants were found in open fire-free shrubland vegetation (Fig. 4, 5). The species was also found in rock crevices on vertical sandstone cliffs; and occasionally in sparsely wooded submontane grassland, in sheltered sites where dry-season fires do not occur every year (Fig. 6).

Eponymy — Gladiolus mariae is named after Maria Alvarez Aguirre, the wife of XvdB.

Fig. 6. Submontane wooded grassland vegetation in the Kounounkan Massif. Gladiolus mariae was collected on this 1020 m high hill and was also observed there, growing on vertical sandstone cliffs. In some years the vegetation on the hill is not subject to the annual dry season fires because it is separated from the main plateau by a narrow, 350 m long canyon. – Photograph taken on 7 Feb 2019 by Xander van der Burgt.

Fig. 5. Inside the submontane shrubland vegetation of Fig. 4. Gladiolus mariae occurs abundantly in this vegetation type. The vegetation is dominated by shrubs that are not resistant to fire: Cailliella praerupticola (in flower), Dissotis leonensis (both Melastomataceae) and Microdracoides squamosa (Cyperaceae). Grasses (Poaceae) are infrequent; the only grass visible is Rhytachne perfecta, front and centre right. – Photograph taken on 27 Nov 2017 by Xander van der Burgt. 

Xander M. van der Burgt, Gbamon Konomou, Pepe M. Haba and Sékou Magassouba. 2019. Gladiolus mariae (Iridaceae), A New Species from Fire-free Shrubland in the Kounounkan Massif, Guinea. Willdenowia.  49(1);117-126. DOI: 10.3372/wi.49.49112

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