Achyranthes mauritiana Moq.

Sukhorukov, Alexander P., Kushunina, Maria, Nilova, Maya V., Baider, Cláudia & Sennikov, Alexander N., 2024, Africa and Arabia encompass a much greater species diversity in the Achyranthes aspera aggregate (Amaranthaceae, achyranthoid clade): Evidence from morphological and chorological data, PhytoKeys 250, pp. 21-94 : 21-94

Achyranthes mauritiana Moq. in DC., Prodr. 13 (2): 313 (1849).

Lectotype (designated here).

Mauritius, [1768–1773], [ Commerson ] s. n. ( P 00487020 [image!]; isolectotypes FI-WEBB 154894 !, G-DC G 00688999 [image!]).

Description.

(Fig. 13 ). Annual (?); stem upright, with spreading lateral branches; leaf petioles 20–40 mm long, blades 30–100 × 20–40 mm, rhombic or elliptic, tip attenuate, almost glabrous or sparsely pubescent at the veins, green, sometimes turning black when dry; inflorescence up to 30 cm long; bract 2.5–3.0 mm long, bracteoles 3.0– 3.5 mm; perianth 4.0–5.0 mm long; stamens 5, anthers ~ 0.4 mm long; style 1.0– 1.2 mm long; fruit 1.7–2.1 mm long.

Taxonomic notes.

The specimens seen are represented by upper twigs only, and our present description is based on the scarce material available in the collections FI-WEBB and MAU. A description provided by Cavaco (1954) is insufficient for any comparison of the material from the Mascarenes, Madagascar and Comoros, because the morphometry of the reproductive characters was not indicated. So far, A. mauritiana is still poorly known. Townsend (1994) synonymized A. mauritiana with A. aspera var. porphyrostachya [≡ A. porphyrostachya ], but this synonymy cannot be accepted due to their different leaf shape and morphometry of the reproductive characters. Only a few old collections cited below were from the Mascarenes, with a more recent collection from Agaléga (Mauritian territory). Nevertheless, A. mauritiana seems to be a distinct species due to its rhombic or elliptic, almost glabrous leaves as compared with A. aspera s. str. Its reproductive characters are the same as in A. aspera s. str. The leaf characters are quite similar to those of A. acuminata , but the morphometry of the reproductive characters is different. Further studies are needed to explore the morphology, phylogenetic relationships and ecology of A. mauritiana .

Townsend (1994) reported A. aspera var. velutina (Hook. & Arn.) C. C. Towns. (≡ A. velutina Hook. & Arn. ) from Réunion. This robust species with villous leaves occurs only in the Pacific. The plants from the Mascarenes resembling A. velutina seem to belong to a different species whose name may be A. borbonica Willd. in Roem. & Schult., Syst. Veg., ed. 15 bis 5: 549 (1819) ≡ A. aspera var. borbonica (Willd. ex Schult.) C. C. Towns., Kew Bull. 29 (3): 474 (1974). The holotype of A. borbonica (“ Insula Borbon ” [ Réunion]) kept at B-W 05-005 - 010 is represented by a small fragment showing villous leaves and an inflorescence collected in a premature stage. This species is also very poorly known, and no other material except for the type of A. borbonica is seen from the Mascarenes.

Nomenclatural notes.

Moquin-Tandon (1849) based his A. mauritiana on two specimens from Mauritius without exact label information (seemingly collected by P. Commerson during his residence on Mauritius in 1768–1773: Frodin 2001), which were kept in the Paris Museum of Natural History and the personal herbarium of Labillardière. Townsend (1994) designated a specimen at G-DC as lectotype. This specimen belongs to the collection from Mauritius, which was previously kept in Paris but obtained by A. P. de Candolle for his private herbarium by exchange in 1821 (cf. de Candolle 1862). Although this specimen is part (a duplicate) of the collection which was used for the original description, it was not cited in the protologue and therefore has no precedence over cited syntypes in lectotype designation. A specimen at P, which was examined by Moquin-Tandon and is accompanied with his analytical drawing, is designated here as a new lectotype in agreement with Art. 9.12.

Distribution.

Mauritius: [without exact location and date] herb. Moquin-Tandon s. n. ( FI-WEBB 154894); Agaléga, North Island, 19 Jul 1976, D. R. Stoddart 7237 ( US 03544411);

Réunion (French Overseas Department): Rivière des Galets, Jul 1851, Boivin s. n. ( MAU 0017619).

General distribution.

The species seems to be endemic to the Mascarenes ( Mauritius and Réunion), but recently collected in Agaléga. Cavaco (1954) cited some records from Madagascar, but all material seen belongs to other species.

Figures

Figure 13. A herbarium specimen of Achyranthes mauritiana (Réunion, Rivière des Galets, Jul 1851, Boivin s. n., MAU 0017619).