Homalopetalum joinvillense Mancinelli & E.C.Smidt, 2015

Mancinelli, Werner Siebje & Smidt, Eric De Camargo, 2015, Homalopetalum joinvillense (Epidendreae; Epidendroideae; Orchidaceae): a new species from Southern Brazil, Phytotaxa 202 (4), pp. 279-283 : 280

Homalopetalum joinvillense Mancinelli & E.C.Smidt , sp. nov., Fig. 1 .

Type:— BRAZIL. Santa Catarina: Joinville, Serra Dona Francisca , Atlantic forest , 2 March 2006, Mancinelli 494- B (holotype JOI) ; idem loco, 26 March 2010, Mancinelli & Zattar 1192 (paratype MBM) .

Haec species ad Homalopetalum alticolum (Garay & Dunsterville 1965: 242) Soto Arenas (2007: 8) accedit sed flore viridi, labello oblongo-obovato, trinervato et clinandrio eroso differt.

Epiphytic herbs. Rhizome 0.5–1 mm long. Pseudobulb 4.5–5 × 1.5–2.5 mm, fusiform to ovoid, green, transversally cylindric, slightly costate, unifoliate. Leaf 6–8 × 2–2.5 mm, conduplicate, cordate, coriaceous, margin entire, revolute and acute in the apex. Inflorescence 2.2–2.3 cm long, terminal, erect, 1-flowered; scape filiform, cylindric; scape bracts tubular, not imbricate, spirally twisted, flower bract tubular. Flower campanulate, resupinate, membranaceous, light green. Sepals free; dorsal sepal 3.5–4 × 2 mm, ovate-elliptical, 3-nerved, margin entire and rounded-cuspidate in the apex; lateral sepals 3.5–4 × 2 mm, ovate-elliptical, 3-nerved, asymmetric, margin entire and rounded-acuminate in the apex. Petals 3–3.5 × 1 mm, oblanceolate, 1-nerved, symmetric, margin entire and rounded in the apex. Lip 5 × 2–2.5 mm, entire, oblong-obovate, 3-nerved, margin slightly denticulate, cuneate in the apex; callus rectilinear, transverse in the basal section of the lip, divided in two parts, globose in the internal part and conical in the external part. Column 2 × 1 mm, alate; anther with 4 equal pollinia; clinandrium erose; column wings completely fused to column foot. Fruit not observed.

Etymology: —The specific epithet refers to Joinville, the municipally where it was found.

Conservation status: —According to the IUCN (2012) criteria this species could be considered Critically Endangered (CR) - criterion B2a - because this species is known from only one locality. The genus Homalopetalum is rare in Brazil and has been collected four times ( Schlechter & Hoehne 1926 and Barros 2004): in 1853 by Pinel (HUH 103182), in 1920 by Hoehne (Hoehne 3899, specimen burned in B) and more recently in 2006 and 2010 by Mancinelli (specimens at JOI, MBM).

The Species Link (2014), Brazilian herbaria (FLOR, FURB, HB, HBR, HCF, HUCP, HUEFS, FUEL, HUEPG, ICN, JOI, M, MBM, PACA, RB, SP and UPCB) and virtual herbaria (BR, CAS, G, GOET, HUH, K, MO, NY, P, S, US, YU and Z) do not provide evidence of additional collections of Homalopetalum in Brazil in the past 80 years, attesting to the rarity of these species.

Discussion: — Homalopetalum joinvillense is recognised by having slightly costate pseudobulbs, cordate leaves, 1-flowered inflorescence, green campanulate flower and lip with a callus that is globose in the internal part and conical in the external part. It is included in this genus based on its small size, its unifoliate psedobulbs and the presence of a column foot. Some combined features differ between this species and the others in the genus: an oblong-obovate and rectilinear lip and a callus that is globose in the internal part and conical in the external part. Homalopetalum joinvillense and H. alticolum which was found in Venezuela ( Dunsterville & Garay 1965) have similar calli; both are rectilinear and divided in two parts, globose in the internal part and conical in the external part. However, in H. alticolum the flowers are white-pink, the lip and other floral pieces have similar length and the clinandrium is entire. Like H. hypoleptum ( Lindley 1853: 1) Soto Arenas (2007: 8) from Brazil, Rio de Janeiro and São Paulo states ( Lindley 1853, Barros 2004), H. joinvillense has green flowers, the lip and floral pieces have the same width:length ratio (1.5:1), and the clinandrium is erose. However, the callus of H. hypoleptum is V-shaped and monomorphic.

Figures

FIGURE 1. Homalopetalum joinvillense Mancinelli & E.C. Smidt. A. Habit. B. Flower. C. Dorsal sepal. D. Lateral sepal. E. Petal. F. Lip with margin detailed. G. Lip and column—lateral view. H. Column—front view. I. Anther—dorsal face. J. Anther—ventral face. K. Pollinia.