Diplacrum blakei K.L.Wilson et R.L.Barrett, 2023

Wilson, Karen L. & Barrett, Russell L., 2023, Revision of the tropical genus Diplacrum (Cyperaceae: Bisboeckelereae) in Australia, Australian Systematic Botany 36 (2), pp. 143-156 : 146-149

Diplacrum blakei K.L.Wilson et R.L.Barrett , sp. nov.

Type: Northern Territory: Kimberley Park Estate, ~ 1.5 km NNE of Elizabeth River bridge on Stuart Highway , 1 May 1983, K.L. Wilson 5055 (holo NSW 2314184; iso DNA D0024243, H, K, P) .

Scleria sp. C B.L. Rye in J.R. Wheeler (ed.) Fl. Kimberley Region 1107 (1992)

Scleria sp. McMinns Lagoon (M.M.J. van Balgooy 1272) P.S. Short, D.E. Albrecht, I.D. Cowie, D.L. Lewis & B.M. Stuckey (eds), Checkl. Vasc. Pl. N. Terr. 28 (2011).

Diagnosis

Nutlets narrow–ellipsoid to narrow–obovoid, with 3 main longitudinal ribs and 3–5 longitudinal ridges between them (not all complete, often more slender and slightly paler in colour), glabrous, glossy; female glumes 1.4–1.8 mm long, including excurved awn 0.4–0.7 mm long; leaves often much exceeding the inflorescence (up to ~2.5 times as long).

Dwarf herbaceous annual, glabrous, 1–6 cm high, with reddish fibrous roots. Culms tufted, more or less erect or spreading. Leaves longer than inflorescences (up to ~2.5 times as long); leaf blades flat, glabrous, margins with sparse, minute, antrorsely aculeate prickle hairs towards apex, 0.3–0.7 mm wide at mid-length, with mid-nerve and 2 lateral nerves prominent on both adaxial and abaxial surfaces; no ligule or contraligule (top of leaf sheath opposite the junction with the blade truncate, not thickened); sheaths green turning straw-coloured with age, occasionally with reddish tinges. Inflorescence approximately the same length as or longer than the culms, composed of several (3 or 4) axillary clusters of spikelets more or less adjacent because of short internodes or occasionally the internodes to 5 mm long and the clusters more distant; each cluster usually with 1 or 2 basal male spikelets and an upper female spikelet. Involucral bract at each node leaf-like, usually much longer than inflorescence. Male spikelets 0.5–0.7 mm long, with 1 slender, more or less hyaline glume 0.5–0.7 mm long, not or scarcely indurated at maturity and reddish-brown; stamen 1; anther 0.2–0.3 mm long, with apical appendage <0.1 mm long. Female spikelets 1.3–1.8 mm long, with 2 glumes encircling the ovary but not tightly clasping the nutlet; peduncle somewhat thickened at apex but rarely cup-like (much less obvious than in D. pygmaeum ); glumes narrow–elliptical with apex broad–acute to obtuse, green becoming straw-coloured with age, with scattered minute red dots, with narrow hyaline margins, 1.4–1.8 mm long including excurved awn 0.4–0.7 mm long, nearly as long as the body of the glume, strongly 3-nerved. Disc triquetrous, white, slightly enlarged at the 3 corners, coinciding with the white thickened base of the 3 ribs of the nutlet, adhering to nutlet. Style 3-fid. Nutlet narrow–ellipsoid to narrow–obovoid, trigonous in cross-section, with 3 main longitudinal ribs and 3–5 longitudinal ridges between them (not all complete, often more slender and slightly paler in colour), glabrous, glossy, dark purplish brown at maturity, 0.4–0.7 mm long, 0.3–0.4 mm in diameter ( Fig. 2 ).

Distribution and habitat

In tropical Queensland, Northern Territory and Western Australia ( Fig. 1 b ). Commonly grows with D. caricinum , D. latzii , D. pygmaeum and other annual sedges on the margins of wet areas (swamps and streams).

Conservation status

Widespread, including in national parks, so not considered at risk. We suggest a status of ‘Least Concern’ (International Union for Conservation of Nature 2019).

Etymology

Named after the eminent Australian cyperologist Dr Stanley Thatcher Blake (1911–1973).

Notes

This is a dwarf sedge like D. latzii and D. pygmaeum , differing most obviously in having longer leaves that exceed the inflorescence (up to ~2.5 times as long), whereas the other species have leaves shorter than the inflorescence. It is similar to D. latzii in nutlet shape and glume awn length, but differs in having numerous longitudinal ribs and ridges on the nutlet ( D. latzii is broadly 3-angled, but is otherwise without ribs). The species is similar to D. africanum in having numerous longitudinal ribs and ridges on the nutlet, but it differs in having a narrower nutlet (more or less broad–ovoid to subglobose in D. africanum ) and a shorter awn on the glumes of the female spikelets (awn ~1.5–2.0 mm long in D. africanum ).

Specimens examined

WESTERN AUSTRALIA: 29.8 km W of Mt Agnes, Prince Regent River Reserve, N Kimberley Region , 26 Mar. 2010, M.D. Barrett and R.L. Barrett MDB 2835 ( PERTH 9401784 ) ; Airfield Swamp, Mitchell Plateau , 1976, R.J. Hnatiuk MP 52A ( PERTH 2331950 ) ; Airfield Swamp, Mitchell Plateau , 1976, K.F. Kenneally 4853, ( PERTH 2332965 ) ; Airfield Swamp, Mitchell Plateau , 1976, K.F. Kenneally 4873 ( PERTH 2332973 ) . NORTHERN TERRITORY: Darwin and Gulf: Arnhem Land , ~ 18 km ESE of Ramingining, 22 June 2001, I.D. Cowie 9429 (DNA D0159871 n.v., NSW 623096 ) ; Arnhem Land , ~ 30 km ENE of Oenpelli on Maningrida road, 30 June 2001, I.D. Cowie 9487 (BRI n.v., DNA D0156881 n.v., MEL n.v., NSW 623112 ) ; Mary River, ~ 13°5′S and 131°47′E, Bull Swamp , 29 Sep. 1946, S.T. Blake 17091 ( BRI-AQ219845 ) ; 17 miles [~ 27 km] N Wilton River Crossing, 15 June 1972, P.K. Latz 2756b (DNA, L, NT 35325 ) ; Elcho Island , 13 July 1975, P.K. Latz 6207 (CANB 257382, DNA D0010249, L n.v., NT 49021 ) ; Kakadu National Park, Buba Billabong , 4 May 1995, N.M. Smith 3706 p.p. ( NSW 1119342 ) ; Kakadu National Park, Gulungul Creek , 5 km WSW of Mt Brockman, 21 Apr. 1980, I.R. Telford 7955 and J.W. Wrigley (CBG 8003335 [CANB], NSW 2314182 ) . QUEENSLAND: Burke: 26 miles [~ 42 km] W of Croydon on the Normanton road, 16 Apr. 1974, R.C. Carolin 8642 (NSW 1119244, SYD) ; 6 miles [~ 10 km] N of Maggieville on the Myravale road, 20 Apr. 1974, R.C. Carolin 8758 (NSW 1119243, SYD) . Cook: Codroy Creek 5.3 km N of Hann River on Laura to Musgrave road, 1 June 1989, J.R. Clarkson 8034 and V.J. Neldner (BRI-AQ591470 n.v., DNA n.v., K n.v., MBA n.v., NSW 2314181 ) ; 4.3 km E of Peninsula Development Road on Pascoe River Road , 23 Apr. 1990, J.R. Clarkson 8565 and V.J. Neldner (BRI n.v., K n.v., MBA n.v., NSW 2314183 ) .

Figures

Fig. 2. Diplacrum blakei. (a, b) Habitat (arrows in b indicate individual plants). (c–e) Habit. (f) Inflorescence. (g, h) Nutlets. Vouchers: (a, b) M.D. Barrett and R.L. Barrett MDB2835 (PERTH); (c, g) R.C. Carolin 8642 (NSW); (d) K.L. Wilson 5055 (NSW, holotype); (e, h) P.K. Latz 2607 (NT); (f) P.K. Latz 2756b (DNA). Scale bars: 1 cm (c, d, e); 1 mm (f); 0.5 mm (g, h). Photos: R.L. Barrett.

Fig. 1. Distribution of Diplacrum species in Australia and Papua New Guinea based on data from the Australasian Virtual Herbarium (see https://avh.ala.org.au/, accessed June 2022). (a) D. caricinum. (b) D. blakei. (c) D. latzii. (d) D. pygmaeum.