Melinis maroccana (Maire & Sam.) M.B.Crespo, M.Á.Alonso & Mart. 2020

Crespo, Manuel B., Alonso, Ángeles & Martínez-Azorín, Mario, 2020, Melinis maroccana (Melinidinae, Paniceae, Poaceae), a new combination for the Moroccan flora, and comments on related taxa, Phytotaxa 433 (1), pp. 77-80 : 77-78

Melinis maroccana (Maire & Sam.) M.B.Crespo, M.Á.Alonso & Mart. -Azorín, comb. nov.

≡ Tricholaena maroccana Maire & Sam. in Maire (1938: 455), basionym [description rounded out in Maire & Samuelsson 1939: 4] ≡ M. repens subsp. maroccana (Maire & Sam.) Zizka (1988: 62)

Type locality:―“ Maroc occidental: Oued Arrimen entre Casablanca et Rabat (J. Gattefossé)” [cf. Maire 1937: 383, sub num. 2361].

Type (lectotype, designated here):― MOROCCO. Aïn Tamda, sur quartzites, vallée de l’Oued Arrimène, Chaouia, km 38 de la route de Casa[blanca] à Rabat , 25 March 1936, J. Gattefossé s.n. ( MPU003969 [digital image!], available at http://mediaphoto.mnhn.fr/media/1442386161164YdCFXpkl1U0Lq5Qq ; isolectotype: P00083453 ! available at http:// mediaphoto.mnhn.fr/media/1442388170943Op5JT5fj9CrgGtTb )

Remarks on typification:― Maire (1938: 455) validly described this species with a short diagnosis: “2595. Tricholaena maroccana Maire et Samuelsson , n. sp. —La plante que nous avons rapportée (Contr. 2361) au T. repens (Willd.) Maire (= T. rosea Nees ) en diffère par ses glumes distantes et constitue une espèce nouvelle, qui sera décrite par les auteurs dans un travail en cours de rédaction”. The reference to “Contr. 2361” points out to material (syntypes) first identified as T. repens (Willd.) Maire , which was collected in “ Maroc occidental: Oued Arrimen entre Casablanca et Rabat (J. Gattefossé)” (cf. Maire 1937: 383, sub num. 2361). The species was later described more in detail ( Maire & Samuelsson 1939) and was indicated from “H.: Skoura (in montibus Djebilet), in rupibus calcareis (E. Wilczek). WS.: Ain Tamda prope Casablanca, in rupibus quartziticis (J. Gattefossé n. 7 c).” Zizka (1988), who accepted Maire & Samuelsson’s (1939) description as the valid protologue, designated a lectotype from among both vouchers cited by those authors: “Typus: Marokko. Ouest-Nord, Ain Tamda près Bouznika: Gattefossé 7c (MPU!, Lecto, B!, P!, Isolecto)”, and annotated the vouchers MPU003970 and B 100168902 as “ lectotype ” and “ isolectotype ”, respectively. However, although those latter vouchers are original material, they do not fit the syntype citation in the true protologue of T. maroccana , since no reference was made to any of those sites by Maire (1938). Therefore, they should not be regarded as syntypes and should be superseded following Art. 9.12 of the Shenzhen Code ( Turland et al. 2018). Accordingly, a new lectotype (“Aïn Tamda, sur quartzites, vallée de l’Oued Arrimène, Chaouia, km 38 de la route de Casa[blanca] à Rabat, 25 March 1936, J. Gattefossé. MPU003969; isolectotype: P00083453) is designated above from among syntypes of T. maroccana according to “Contr. 2361”, which matches perfectly the protologue of the species.

Diagnostic characters:― Melinis maroccana much differs and is easily distinguishable from the other members of the M. repens (Willd.) Zizka aggregate by the stems shorter and slender (up to 450 × 1.3 mm); leaf ligule with shorter hairs (0.5−0.8 mm); inflorescence a narrow, dense and contracted panicle 6.5−9 × 2−3 cm; spikelets medium-sized (3.5−5 mm long), greyish to olive-greenish, with a dense indumentum of appressed trichomes exceeding up to 1.5 mm the spikelet apex; upper glume prominently nerved, muticous or with a short, inconspicuous awn or mucro up to 0.1 mm long; internode between both glumes (0.5−) 0.6−0.8 mm long; lower lemma cartilaginous to subcoriaceous, truncate to slightly emarginated at apex, muticous or with a short, inconspicuous awn or mucro up to 0.1 mm long ( Table 1 ).

Distribution and ecology:―This species is endemic to western Morocco, namely from Aïn Tamda near Casablanca to El Kelaa des Sraghna near Marrakech. It occurs on rocky slopes and stony places, mostly in open quartzitic and limestone substrates at low elevation, between ca 50 and 500 m.

Additional studied material:― MOROCCO. Aïn Tamda , prés de Casablanca, rochers quatzitiques [sic], 50 m, 11 April 1937, R. Maire & M. Weiller 3290 (MPU049952 [digital image!], MPU414072 [digital image!], P01919832!, P02352230!) ; rochers à Ain Tamda , près Casablanca, April 1937, Weiller, Gattefossé & Maire 342.37 (MPU051161 [digital image!]) ; in rupibus arenaceis Aïn Tamda prope Casablanca, 11 April 1937, R. Maire s.n. (MPU049951 [digital image!], P00083537!) ; Chaouia , rochers quartzitiques de l’Aïn Tamda, 1 June 1937, J. Gattefossé s.n. (B 100168902 [digital image!], as “ isolectotypus ” by G. Zizka 1988) ; Quartizites à Aïn Tamda, pres Bouznika, 1 June 1937, J. Gattefossé s.n. (MPU003970 [digital image!], as “ lectotypus ” by G. Zizka 1987; MPU027476 [digital image!]; S-G-6171) ; route de Marrakech, El Kelaa , kil. 46, rochers schisteux, 7 April 1928, E. Wilczek s.n. (MPU049950 [digital image!]) .

Taxonomic relationships: ―As shown by Zizka (1988), Melinis maroccana belongs to the aggregate of M. repens . This group of African and southwestern Asian plants is accepted to include four taxa morphologically close, which have been treated in diverse taxonomic ranks. The most relevant characters to differentiate taxa in the M. repens aggregate are shown in Table 1 . Some of them prove to be diagnostic for taxa recognition, such as the length of the leaf ligule hairs; the inflorescence morphology; the spikelet size, colour and indumentum; the morphology, consistence and venation pattern of both the upper glume and the lemma of the lower floret; and the length of the awn on the upper glume. Evaluation of morphological features in the context of the genus Melinis leads us to accept a different taxonomic arrangement for the aggregate, including three species and one additional subspecies: M. grandiflora (Hochst.) Hackel (1901: 464) , M. maroccana , and Melinis repens (with subsp. repens and subsp. nigricans ). First, Melinis maroccana is easily distinguished by its shorter ligule hairs; smaller, denser and contracted panicle; medium-sized spikelets with indumentum of appressed to erect hairs slightly exceeding the spikelet apex; upper glume prominently nerved, muticous or with an inconspicuous awn or mucro up to 0.1 mm long. This latter one is perhaps the most remarkable character, allowing safe identification. Such combination of characters together with an isolated distribution in western Morocco (the northern most in the rank of the whole aggregate) support recognition at species rank. This Moroccan endemic shares some characters (e.g. ligule hairs length, slender stems, or the cartilaginous to coriaceous upper glume with prominent ribs) with M. grandiflora , a species well-characterised by its large spikelets (the largest in the aggregate, from where the specific epithet comes), which often bear an indumentum of erect long hairs not much exceeding the spikelet apex; both glumes are conspicuously distant (up to 2 mm apart) and are the largest in the aggregate, the upper one shows a conspicuous, long apical beak, and also an awn up to 14.5 mm long which is again the longest in the aggregate. This latter species is widely distributed in the eastern half of Africa and the Arabian Peninsula, with some scattered locations in western Tropical Africa and Cape Verde. The third species is M. repens s.l., a morphologically variable species that can be easily recognisable by a combination of characters, such as the often robust stems; the leaves with often wider blade; the ligule with longer hairs; the inflorescence broader and loose; the spikelets medium-sized, usually long patent-hairy (occasionally glabrescent to subglabrous); the upper glume and lower flower lemma membranous to slightly cartilaginous, with inconspicuous to slightly prominent ribs; and the upper glume showing sometimes a moderate beak about ¼ to ½ the length of the glume, with a conspicuous apical awn up to 6 mm long (much longer than in M. maroccana , but much shorter than in M. grandiflora ). Nonetheless, the intraspecific variation in M. repens fits with two morphological patterns that can be assigned to two subspecific taxa as defined by Zizka (1988): M. repens subsp. repens and M. repens subsp. nigricans . The latter often shows more robust and taller stems, broader leaves, and darker coloured spikelets (from where its name comes) with a sparse indumentum of shorter hairs (occasionally glabrescent to subglabrous). Both subspecies occur in ruderal anthropogenic habitats, and sometimes are sympatric. However, Melinis repens subsp. nigricans is restricted to central Africa and is also found in humid riparian habitats. Because the differential characters are weak and numerous transitional individuals are found between both morphological extremes, the subspecific treatment seems a proper choice for both taxa.