Disakisperma yemenicum (Schweinf.) P.M. Peterson & N. Snow, 2013

Snow, Neil, Peterson, Paul M. & Romaschenko, Konstantin, 2013, Systematics of Disakisperma (Poaceae, Chloridoideae, Chlorideae), PhytoKeys 26, pp. 21-70 : 51-53

Disakisperma yemenicum (Schweinf.) P.M. Peterson & N. Snow comb. nov. Figure 5A-Q

Eragrostis yemenica Schweinf., Bull. Herb. Boissier 2 (App. 2): 41. 1894. Cypholepis yemenica (Schweinf.) Chiov., Annuario Reale Ist. Bot. Roma 8(3): 357-358. 1908. Eleusine yemensis (Schweinf.) Chiov., Ann. Bot. (Rome) 10: 410. 1912. Coelachyrum yemenicum (Schweinf.) S.M. Phillips, Kew Bull. 37(1): 159. 1982.

Leptochloa appletonii Stapf, Bull. Misc. Inform. Kew 6: 223. 1907. TYPE: SOMALIA. Golis Range, Drake-Brockman 147 (lectotype: G (photo)!, designated here).

Eragrostis diplostachya Peter, Repert. Spec. Nov. Regni Veg. Beih. 40 (1, Anhang): 100, t. 58, f. 1. 1929. TYPE: TANZANIA. Lushoto District, Buiko, Peter 11083 (lectotype: B designated by S.M. Phillips, 59. Cypholepis , Gramineae , part 2, Fl. Trop. E. Africa 250. 1974; K-photo!).

Type.

YEMEN.Arabia Felici, 2 Feb 1889, G.A. Schweinfurth 1332 (lectotype: G-photo! designated here, S.A. Chaudhary, Grasses of Saudi Arabia 274. 1989, earlier cited no specific herbarium). We are choosing the G specimen as the lectotype because it is easily seen (electronically), was previously selected by Chaudhary (1989), and the orginal collection at B was destroyed.

Description.

Perennials. Culms 30-100 cm tall, 1-2 mm wide at base, usually flattened, erect, infrequently decumbent or sprawling, arising from fibrous roots, culms unbranched or only as tillers from very base; nodes glabrous; internodes 4-14 cm long, soft, hollow. Leaf sheaths longer or shorter than the internodes, round or slightly flattened, glabrous on the sides and margins; collar green or tan; ligules 0.5-1 mm long, membranous, erose or lacerate, apex truncate; blades 7-32 cm long, 2.5-5.5 mm wide, cauline, linear, flat but becoming folded to loosely involute, scaberulous with scattered, delicate, straight hairs near base above, the hairs 3-5 mm long, glabrous to scaberulous below, often disarticulating at base, midrib prominent. Panicles 3.5-19 cm long, 1.0-3.0 cm wide, exserted at maturity, composed of 2-8 racemosely arranged branches; branches 2-7 cm long, alternate along rachis, rachis often somewhat zig-zaged from each spikelet insertion to the next, steeply ascending to erect, rigid, axis scabrous. Spikelets 5-10 mm long, pedicels mostly less than 0.5 mm long, usually imbricate, 7-12-flowered; callus glabrous; glumes 2-3.8 mm long, subequal, 1-nerved, membranous, lanceolate to narrowly ovate, scabrous on midnerve, the midnerve dark green; apex acute to obtuse; rachilla joint cartilaginous and expanded above; lemmas 2.5-4.7 mm long, usually 3-nerved, membranous above, lower margins cartilaginous and involute, ovate, pale green with dark green nerves, often tinged with dark or olive-green, glabrous above and appressed pilose on lower half, the hairs clavicorniculate, apex obtuse to subacute, awnless; paleas 1/2-2/3 as long as the lemma, ovate, longitudinally bowed-out, the keels ciliolate, dorsal surface glabrous or with appressed clavicorniculate hairs on the lower half, apex obtuse. Anthers 0.2-0.3 mm long, yellowish. Lodicules about 0.2 mm long. Caryopses 1.2-1.5 mm long, 0.7-0.9 mm wide.

Leaf anatomy. Watson and Dallwitz (1992) reported C4, XyMS+ anatomy with centripetal chloroplasts. Midribs conspicuous with colorless cells, having a conventional arc of bundles (a large bundle, flanked on each side by two smaller bundles). All vascular bundles accompanied by sclerenchyma ( Watson and Dallwitz 1992; Snow unpublished). Bulliforms present in simple fans.

Stem anatomy. Not known.

Chromosome number. Not known.

Phenology.

Flowering July through December.

Distribution.

Native: Saudia Arabia, Oman, Yemen, Eritrea, Ethiopia, Somalia, Kenya, Tanzania, and South Africa; growing in Acacia and miombo woodlands on dry, shallow, often stoney soils among rocks, often in disturbed habitats ( Phillips 1974b). Elevation 250-2100 m. (TDWG: CPP, ERI, ETH, KEN, OM, SAU, SOM, TAN, YEM.)

Non-native: Not known.

Conservation status.

Least Concern ( IUCN 2010).

Etymology.

The epithet refers to Yemen, the geographical origin of the holotype.

Vernacular name.

Suggested: Yemen’s Jacobsgrass.

Comments.

Disakispermum yemenicum most closely resembles Disakisperma eleusine by virtue of the ascending to erect panicle branches, but the base of the lemma of Disakisperma yemenicum is cartilaginous, the base of the leaf blade adaxially has delicate straight hairs mostly 3-5 mm long, and its anthers are less than 0.5 mm long (vs. 0.9-1.0 mm in Disakisperma eleusine ). We have examined relatively few specimens of Disakisperma yemenicum given that initital herbarium studies did not believe it was a part of Leptochloa s.l. ( Snow 1997).

Specimens examined.

Eritrea.Assaorta, A. Pappi s.n. (US); Ocule, A. Pappi 5239 (US). Kenya. 6 mi SW of Nairobi, Nairobi National Park, S.L. Hatch 4220 (TAES, US). Somalia. Buramo, J.B. Gillett 4872 (US); Daganyado, P.E Glover & H. Gilliland 745 (US). South Africa. Cape Province, Boetsap Barkly West, A. Brueckner 143 (US); Kimberley Div. M. Wilman s.n. (US); Farm Rosenthal Mopane, L.E.W. Codd 4455 (US); North Cape, A. Brueckner 1032 (US). Tanzania. Shinyanga Region, Serengeti National Park, Naabi Hill, Peterson, Soreng & Romaschenko 24254 (DSM, US).

Excluded names

Leptochloa digitatiformis Beetle, Phytologia 52: 14. 1982. TYPE: Mexico, Sonora, Mpio. Fronteras, ejido km 47 km, Bernal & Cuadra s.n. (holotype: SARH, A. Beetle pers. comm. to N. Snow in 1993, but not found there by Snow).

Comment.

The status of this taxon is not entirely certain since we cannot locate the type for study (see comments above under species).

Diplachne dubia var. humboldtiana Kuntze, Revis. Gen. Pl. 3(2): 349. 1898. Leptochloa dubia var. humboldtiana (Kuntze) Beetle, Phytologia 54: 4. 1983. TYPE: Mexico.

Comment.

We have been unable to locate a type for this name (but not at NY; P.M. Peterson, pers. obs., 2013).

Figures

Figure 5. Disakisperma yemenicum (Schweinf.) P. M. Peterson & N. Snow A habit B sheath, ligule, and blade, ventral view C branch of inflorescence with glumes D spikelet E lower glume F upper glume floret, ventral view G floret, lateral view H floret, central view I lemma J palea with rachilla joint K palea, ventral view L pistil and stamens M caryopsis, lateral view N caryopsis, dorsal view O caryopsis, cross section P caryopsis, ventral view. Drawn from Peterson, Soreng & Romaschenko 24254 (US).