Eleocharis endounifascis Hinchliff & Roalson, 2010

Hinchliff, Cody E., Petersen, Stephanie & Roalson, Eric H., 2010, Eleocharis endounifascis: A new species of Eleocharis subgenus Limnochloa (Cyperaceae) from northern South America., Phytotaxa 7, pp. 19-24 : 20-23

Eleocharis endounifascis Hinchliff & Roalson , sp. nov. ( Fig. 1 & Fig. 2 )

Species haec ab Eleocharis interstincta differt in filamentis vascularibus culmorum centralibus singularibus et in spiculis acuminatis et in squamis spicularum margine superne hyalines inferne in liniis teaniformibus fuscatis.

Type: — BRAZIL. Ceará: Municipio de Fortaleza, Parangaba , shallow water of lake, 11 October 1935, F. Drouet 2605 ( US!- holotype) .

Plants perennial, erect from trailing rhizomes 16.4–32.5 cm long (between fascicles of culms) × (2.6–)3.2–6(–6.6) mm wide. Culms 5.6–9.4 cm long × 1.5–4.8 mm wide, more or less terete, but often becoming somewhat flattened to obscurely 3-angled near apex, bearing regularly spaced complete transverse septae and a single central vascular bundle that extends from the base to the apex of the culm, perforating each internal septum. Leaf sheaths (2.6–) 7.6–22.7 cm long, apex oblique, with acute to acuminate tip appressed to culm. Spikelets 15.3–39.2 mm long × 3.4–5.6 mm wide, basally cylindric, tapering to an acuminate apex, nearly as wide as culms (at least at base), (22–)27–136-flowered, not proliferous. Lower scale infertile, cartilaginouscoriaceous, often with hyaline margin, more or less continuous with culm surface but sometimes subtended by a very slight constriction, similar in length to upper scales but much wider, typically amplexicaulous. Upper scales (2.2–)2.4–4.6(–5.2) mm long × (2.0–)2.2–3.4(–3.6) mm wide, cartilaginous, not keeled, with rounded to occasionally nearly truncate apex, layered so densely in spikelet so that only the top ¼ th to ⅓ rd or less of each scale is visible, giving the superficial appearance of scales that are much wider than tall, though this is not actually the case; upper scales more or less evenly yellowish green when immature to centrally bright green becoming yellowish brown towards margins at maturity, abaxial surface usually marked with 6–16 inconspicuous nerves that converge near the apex and a single conspicuous midvein; adaxial surface of upper scales frequently speckled with dark reddish-brown dots, some specimens with a few dark brown speckles on the abaxial surface as well, conspicuous hyaline margin frequently present, 0.1–0.4(–0.5) mm wide (but often much wider below the visible portion of the scale), usually in conjunction with 0.1–0.2 mm wide dark brown submarginal band. Perianth bristles 7–8, pale cream color at the base to light reddish-brown above, (0.6–)1.3– 2.4(–2.6) mm long, only slightly exceeding the nut including the style base, if at all, with recurved spinules. Stamens 3, anthers (1.4–) 1.5–1.9 mm long. Style trifid. Nuts (1.7–) 1.8–2.3 mm long (including style base) × 0.9–1.1 mm wide (at widest point), sub-lenticular, with adaxial face often flatter and abaxial face more rounded, obovoid to obpyriform, apex constricted to a short neck, nut markedly sculptured at 10–15×, reticulate, the adaxial surface with 14–20 longitudinal rows of transversely-oblong, hexagonally-shaped cells separated by prominent ridges, these cells generally about twice as wide as they are tall; nut stramineous to dark brown, shiny. Style base (tubercle) 0.3–1.4(–1.7) mm long × 0.4–1.0 mm wide at base, high pyramidal, laterally compressed.

Distribution:—The species range is not well known due to the low number of collections. It occurs at least from southeastern Venezuela east into Guyana and south into Brazil. Collections are known from northeastern coastal Brazil, and the species probably occurs in Suriname and possibly French Guiana as well. Da Silva et al. (in press) also mention a plant fitting the description of E. endounifascis from Pernambuco, Brazil, with “…hollow and septate culms, but with an evident central vascular bundle,” though we have not verified the identity of these specimens (from the cited publication: Eleocharis sp. 3 , chromosome count 2 n = 42). Košnar et al. (in press) also describe plants that are apparently hybrids between E. endounifascis and E. cellulosa and E. interstincta in Belize. Košnar et al. clearly recover ITS copies identical to E. endounifascis , but whether pure representatives of this species continue to exist in Belize is unclear from the data presented.

Etymology:—The epithet refers to the solitary central vascular bundle that is suspended in the middle of each culm’s intracellular air space by its complete internal transverse septae.

Additional specimens examined:— GUYANA. Cuyuni-Mazaruni : Isseneru, Lower Mazaruni River, ~6.365˚ N, 60.380˚ W, 27 September 2006, K. Redden 4362 ( US, WS); Kamakusa, Upper Mazaruni River , ~ 59º50’W, 11–22 July 1923, J. S. de la Cruz 4241 ( UC) . VENEZUELA. Anzoátegui : Mun. Freites: Morichal Morichalote, fundo Mis Aidas , 6–7 km al oeste de Oritupano , 9º02’N 63º30’W, 110–120 m, 23 February 1998, A. Fernández & C. Reyes 12359 ( US) . BRAZIL. Rio de Janeiro : Mun. Cabo Frio: Cabo Frio, Praia do Pontal , 22 56’48”S 42 1’54”W, ao nivel do mar, 17 April 1952, L. B. Smith 6.558 ( US) .

Discussion:— Eleocharis endounifascis forms large colonies, which spread via trailing subterranean or submerged aquatic rhizomes. Fruiting appears to occur more rarely in this species than other Limnochloa , and among the five herbarium specimens examined in the preparation of this description; only one had produced mature nuts. A cultivated plant in a heated glasshouse at Washington State University has flowered regularly for two years but has similarly failed to ever produce nuts, suggesting either self-incompatibility or a lack of appropriate environmental stimuli for fruit maturation. In the wild, the plants have been found growing in standing water in disturbed, open habitats occurring among a mosaic of wet forest on nutrient-poor white sands substrate. Like most species of subgenus Limnochloa , they seem to prefer seasonally inundated wetlands, and probably flourish under low to moderate disturbance regimes, in full sun and still or slowmoving shallow water.

This species is included in Eleocharis subgenus Limnochloa on the basis of its clasping lower scale that appears to be a continuation of the culm, unkeeled upper scales with a distinct hyaline margin, and achene ornamentation in the form of depressed polygonal cells. Molecular phylogenetic studies have verified the placement of this species in subgenus Limnochloa , apparently closely related to E. mutata (L.) Roemer & Schultes (1817: 155) and E. spiralis (Rottb.) Roemer & Schultes (1817: 155) , however this relationship is only moderately well-supported ( Hinchliff & Roalson 2009, Roalson et al. in press).

Eleocharis endounifascis is superficially similar to Eleocharis interstincta (Vahl) Roemer & Schultes (1817: 149) , and has been frequently misidentified as such, because these two species are the only Eleocharis subgenus Limnochloa species in South America that have septate culms. Eleocharis endounifascis can be readily and easily distinguished from E. interstincta by the presence of a single, central vascular bundle in each culm that runs the length the culm and perforates all the internal septae near their center, and by its characteristically tapered, acuminate spikelets, which bear scales that usually show a strongly differentiated, darkened submarginal band below their hyaline margins.

Nucleotide sequence data from Eleocharis endounifascis have been utilized into two recent molecular systematics publications ( Hinchliff & Roalson 2009, Roalson et al. in press). This species, which has been referred to as E. sp. nov. “ Guyana ” or simply E. sp. nov., is represented by the following GenBank nucleotide sequences: FJ826591 ( ITS), FJ829398 (trnC-ycf6), and FJ829441 (ycf6-psbM) .

Figures

FIGURE 1. Eleocharis endounifascis A. Habit. B. Cross section of dried stem showing central vascular bundle. C. Mature spikelet. D. Scale. E. Achene including bristles and residual stamen filaments. F. Achene with bristles removed, showing pattern of surface reticulations. (Drawn from F. Drouet 2605 [US]).

FIGURE 2. Photos of Redden 4362 taken in the field in Guyana, 2006. All by C.E. Hinchliff. A. General habit, plants shown growing at margins of shallow pond. B. Culm bases with intact leaf sheaths. C. Culm apices. The arrow shows an undeveloped spikelet on a mature culm, which is a common characteristic feature of this species. D. Mature spikelet.