The genus Callitriche (Plantaginaceae: Callitricheae) in South America Author Lansdown, Richard V. 0000-0003-0984-4552 Ardeola Environmental Services, 45 The Bridle, Stroud, Gloucestershire, GL 5 4 SQ, United Kingdom & Honorary Research Associate, Royal Botanic Gardens, Kew, Richmond, Surrey, TW 9 3 AE, United Kingdom & r. lansdown @ kew. org; https: // orcid. org / 0000 - 0003 - 0984 - 4552 r.lansdown@kew.org Author Hassemer, Gustavo 0000-0003-4365-6934 Câmpus de Três Lagoas, Universidade Federal do Mato Grosso do Sul, CEP 79613 - 000, Três Lagoas, MS, Brazil & g. hassemer @ ufms. br; https: // orcid. org / 0000 - 0003 - 4365 - 6934 g.hassemer@ufms.br text Phytotaxa 2021 2021-05-19 501 1 85 118 http://dx.doi.org/10.11646/phytotaxa.501.1.3 journal article 10.11646/phytotaxa.501.1.3 1179-3163 5424744 8. Callitriche ecarinata Lansdown & Hassemer , sp. nov. Type: — VENEZUELA . MÉRIDA : Sierra Nevada , Laguna de los Anteojos , 4900 m , 2 November 1976 , L. Bernardi et al. 16975 ( holotype G barcode G00414944!) . Diagnosis: — Callitriche ecarinata can be distinguished from all other Callitriche species by the combination of unwinged, subsessile fruit which are not strumose, orange when mature, 0.6–1.0 mm high, widest in the middle, wider than high, with ♂ and ♀ flowers in the same aXils and the stYle < 2.7 mm long. Description: —Stem and leaf scales present. Leaves joined across stem. Lingulate leaves 4.4 × 0.8 mm , expanded submerged, or floating leaves 1.8–3.3 × 0.8–1.9 mm , petiole 0.3–3.5 mm long, venation simple, the apical leaves forming a floating rosette, leaves of terrestrial plants 1.0–1.8 × 1.0– 1.2 mm . UsuallY a ♂ and ♀ flower in one aXil opposed bY a solitarY ♀ . Bracts caducous, 0.5–0.7 mm . StYles persistent, ≤ 2.7 mm long. Filament ≤ 3.6 mm ; anther 0.2–0.4 mm diameter; pollen yellow. Fruit not strumose, subsessile, wider than high, orange when mature, 0.6–1.0 × 0.8–1.2 mm , unwinged. Illustrations: — Figure 1 (i). Distribution: — Callitriche ecarinata occurs along the spine of the Andes from Mérida in Venezuela to Ambato in Ecuador , with an isolated occurrence in the Sierra Nevada de Santa María in northern Colombia . It is known from six gatherings, one from Venezuela , five from Colombia and one from Ecuador . Known altitudinal range: 3000–4900 m . Etymology: —The specific epithet means “not keeled” referring to the unwinged fruit. Notes: — Callitriche ecarinata is very poorly known and poorly represented in herbaria. There is a need to survey potentially suitable habitat to try to find more populations. Conservation status: —Available information is inadequate to derive an informed assessment of the conservation status of Callitriche ecarinata and it is therefore classed as Data Deficient (DD). Additional material studied ( paratypes ): — COLOMBIA . BOYACÁ: Damp bank at streamside in páramo above Quebrada de las Playas , Sierra Nevada del Cocuy , 8 August 1957 , P.J. Grubb et al. 332 (K, US). CAUCA: Municipio de Purace , Volcan de Purace , 3850–4500 m , 5 October 1984 , G. Lozano et al. 4582 (P barcode P04156182). CUNDINAMARCA: Alrededores de la laguna de Los Tunjos , vereda Santa Rosa , Parque Nacional Sumapaz 4º 16’ 35” N , 74º 12’ 17” W , 3500 m , 8 August 1998 , P. Pedraza 275 (HUA). MAGDALENA: Trailing stems submerged or on surface of muck in center of valley, in a Bosque Pluvial Montano/Paramo Pluvial Subalpino transition zone with approx. 2000 mm /year rainfall, Valley of Rio Guiachinacopunameina , 73º 40’ W , 10º 44–45’ N, 3500–4000 m ., 28 May 1977 , S. White & W.S. Alverson 632 (NY). ECUADOR . TUNGURAHUA : Creeping and forming mat just beneath the water, anthers above surface, on well-trodden path through ‘165’ just north of Lake , by Lake Aucacocha , Llanganati Mountains [Cordillera de los Llangenates], 3000 m , July 1969 , P.J. Edwards 49 (K) .