Callitriche concinna Lansdown & Hassemer 2021, sp. nov.
Creators: name: Lansdown, Richard V.
name: Hassemer, Gustavo
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Lamiales
Plantaginaceae
Callitriche
Callitriche concinna

description: 5. Callitriche concinna Lansdown & Hassemer, sp. nov.   
 Type: — ARGENTINA. CHUBUT: [illegible], Lago Vintter, Dpto. Tehuelcher, 19 March 1994, E.G. Nicora 10010 (holotype SI-063690!).   
 Diagnosis: — Callitriche concinna differs from all other members of the genus in the broadly-winged, very uniform, medium-sized fruit which are brownish-black at maturity and intermediate in size between those of C. rimosa Fassett (1951: 211) and C. turfosa. It can be distinguished from C. rimosa by the fact that the wing does not extend into the commissurial groove and from C. turfosa by its development of submerged and floating leaves, the complex venation and presence of bracts.   
 Description: —Stem and leaf scales present. Leaf bases connate. Lingulate leaves unknown, expanded submerged or floating leaves ellipsoid, 1.9–10.8 mm × 1.2–5.1 mm, petiole 0.8–5.3 mm long, venation fairly simple with a few loops and anastomosing veins outside the secondary veins, the apical leaves forming a floating rosette, leaves of terrestrial plants 1.1–2.8 mm × 0.8–1.6 mm. 1 ♂ and 1 ♀ flower in most aXils. Bracts persistent, 0.5–0.8 mm long. StYle erect to spreading ≤ 1.5 mm long. Filament erect, ≤ 1.9 mm long; anther size unknown; pollen Yellow. Fruit not strumose, subsessile or on pedicel to 0.5 mm, more or less as wide as long, brownish-black when mature, contrasting with pale wing, 0.6–1.2 × 0.8–1.2 mm, broadly winged throughout, wing pale contrasting with dark fruit.   
 Illustrations: — Figure 1 (f).   
 Distribution: —The geographical distribution of Callitriche concinna is not clear, confirmed specimens have been collected from Buenos Aires, Chubut and Entre Ríos provinces of Argentina, as well as from Chile and Uruguay. It seems likely therefore that it has a relatively wide distribution from central Chile and Chubut Province in Argentina north to north-eastern Argentina and Uruguay. There are no altitude data available.   
 Etymology: —The name means neat or tidy and refers to the uniform, evenly and broadly-winged fruit in which the pale wing contrasts strongly with the rest.   
 Notes: — Callitriche concinna has typically been included within either C. rimosa or C. turfosa by other authors. It is relatively poorly represented in herbaria but is typically abundantly fertile so that specimens generally include large numbers of fruit.   
 Conservation status: — Callitriche concinna is classed as Least Concern (LC) as it appears to have a broad geographical distribution with no evidence of threats which could cause its extinction.   
 Additional material studied (paratypes): — ARGENTINA:BUENOS AIRES: [illegible], Hudson (F.C.S.) 3 October 1931, L.R. Parodi 9923 (GH); in pantanos, San Isidro, 20 October 1930, L.R. Parodi 9561 (GH); semiflotante en [illegible], Parana mini, Buenos Aires, 22 September 1956, A.E. Burkart 20027 (SI-063672). CHUBUT: Muy [illegible] en el bosque, en la toma de aqua, Lago Vintter, dpto. Tehuelcher, 30 January 1992, E.G. Nicora 9678 (SI). ENTRE RÍOS: Camino al balneario El Nandubaysal, Gualeguaychú, Dep. Gualeguaychú, 25 October 1977, N. Troncoso et al. 2140 (SI-065627); Concepción del Uruguay, 7 November 1877, P.G. Lorentz 851 (F-63757 barcode V0356633 F, K, P barcode P04214866, STU-31883). CHILE. M. Gay s.n. (K, P barcode P04214836); Punta Frias [?], 20 January 1904, Hicken s.n. (SI-095408). URUGUAY. Greges deusos en lugar humedo, [illegible], Florida, 22 December 1936, B. Rosengurt 782 (F, GH).
description: Published as part of Lansdown, Richard V. & Hassemer, Gustavo, 2021, The genus Callitriche (Plantaginaceae: Callitricheae) in South America, pp. 85-118 in Phytotaxa 501 (1) on pages 94-95, DOI: 10.11646/phytotaxa.501.1.3, http://zenodo.org/record/5424744