Callitriche heterophylla Pursh (1814: 3)

Lansdown, Richard V. & Hassemer, Gustavo, 2021, The genus Callitriche (Plantaginaceae: Callitricheae) in South America, Phytotaxa 501 (1), pp. 85-118 : 98-99

10. Callitriche heterophylla Pursh (1814: 3)

Type: — UNITED STATES OF AMERICA. PENNSYLVANIA: Aquatic herb in running water in rocky stream edge, Loyalsock Creek near Ogdonia , Hillsgrove Township , Sullivan County, ca. 800 ft, 10 June 1979, T. Plowman 7836 (neotype [designated here] BM barcode BM010763506!) .

Description: —Stem and leaf scales present. Leaf bases connate. Lingulate leaves often long and very fine, 4.1– 24.7 × 0.3–1.1 mm, expanded submerged or floating leaves, obovate or oblong, often of a very characteristic shape, with broadly spathulate blade tapering very abruptly to petiole, occasionally tapering gradually into petiole 3.7–7.0 × 1.0– 3.5 mm, petiole 2.5–5.2 mm long, venation complex with numerous loops and anastomosing veins outside the secondary veins, apical leaves forming a floating rosette, leaves of terrestrial plants 4.1–6.2 × 0.7–1.0 mm. Flowers usuallY solitarY or 1 or more ♀ and 1 ♂ in an aXil. Bracts caducous, falcate or ovate, (0.10–) 0.13–1.30 mm. StYles persistent or caducous, erect or spreading, ≤ 6 mm long. Filaments ≤ 3.8 mm; anther reniform or orbicular, 0.2–0.4 mm wide; pollen yellow. Fruit not strumose, subsessile, as wide as long, black when mature, 0.45–1.20 × 0.45–1.20 mm, wing absent or only at apex, 0.05–0.10 mm wide.

Illustrations: —plates 1167(4), 1168 and 1173(13) in Fassett (1951); Figure 3 (a–i) in Bacigalupo (1979b); Figure 1 (k).

Distribution: —This species was thought to be endemic to the Americas, occurring from northern Canada and Greenland south throughout much of North America, through Central America to Chile and Argentina ( Lansdown 2009, Lansdown & Christenhusz 2011). However, it occurs in the Kuril Archipelago and Kamchatka (specimens at NY) suggesting that it may also be native to the eastern seaboard of Russia. It occurs as a non-native in New Zealand. Known altitudinal range: 100–4600 m. See maps on pages 176 and 178 in Fassett (1951).

Notes: —Frederick Pursh (1814: 3) was the first to use the name Callitriche heterophylla , providing a brief description of vegetative parts and linking it to “ C. verna Willd. ” but not to any specimen, while Willdenow cited the name C. verna as sensu von Linné (1753) which refers to C. palustris . Darby (1841) was the first to take up the name C. heterophylla providing a better description, including the bracts, such that of the species in the region referred to, his description could refer only to C. heterophylla ( Fassett 1951) . Hegelmaier (1867) and G. Engelmann who were in correspondence regarding the genus Callitriche adopted the name in the sense used by Pursh, listing C. asagraei Hegelmaier (1864: 54–55) as a synonym but not referring to C. brevifolia Pursh (1814: 3–4) or C. linearis Pursh (1814: 3) . Pursh’s material is mainly at K or PENN ( Ewan 1951) but searches have failed to locate any material collected by Pursh and representing the names C. brevifolia , C. heterophylla or C. linearis (F.W. Pennell and E. Salisbury in litt. to N.C. Fassett 1951). The only material seen from the area in which Pursh was active is all part of the original material of C. austinii Engelmann (1867: 428) and which would therefore not be suitable as a neotype for C. heterophylla . The specimen T. Plowman 7836 (BM barcode BM010763506) is a good example of typical material of C. heterophylla and is here selected as a neotype.

As is the case with many very common Callitriche species , such as C. palustris , C. stagnalis and C. rimosa , C. heterophylla is very variable, to the extent that Fassett (1951) recognised two subspecies, although biometric data suggest that the distinction is not valid ( Lansdown 2019). In North America, the fruit of some populations of C. heterophylla approach C. palustris to the extent that some herbarium material cannot be separated. Similarly, in southern South America, some gatherings of C. heterophylla superficially approach C. antarctica to the extent that only the characteristically robust growth of C. antarctica serves to distinguish them. The similarity of the fruit of these two species is striking and may indicate a common origin.

Callitriche heterophylla can be distinguished from other Callitriche taxa in the region by the small, unwinged fruit combined with the long stYles (≤ 6 mm long) and filament (≤ 3.8 mm) as well as often bY the characteristic shape of floating expanded leaves. Some populations resemble C. antarctica but can be distinguished by the delicate leaves which are connate but do not form a cup at the base. Occasional populations show a distinct wing at the apex of the fruit, it is not clear whether this has a genetic basis.

Conservation status: — Callitriche heterophylla is classed as Least Concern (LC) because it is widespread and at least locally abundant and faces no know significant threats.

Additional material studied: —[only South American specimens listed] ARGENTINA. Mlle. Gonnot 123 (P barcode P04214953); in small pool containing rainwater (as opposed to the lake water containing glacial sediment) near the edge of Largo Argentino in a recently flooded area, Lago Frio (Brazo Sur), 300 ft., 1958–1959, Shipton Expedition to Patagonia (Largo Argentino), P.W.James 782 (BM); JUJUY: De ceimenento a Palma Sole, Jujuy, Dpto. Santa Barbara, 16 November 1992, R. Kiesling 8280 (SI). RÍO NEGRO. In Lago los Candados, 30 cm deep, Parque Nacional Nahuel Huapi, Puerto Blest, 750–800 m, 2–3 January 1979, S. Laaegaard 12877 (K, NY). BOLIVIA. LA PAZ: Forming mats, submerged in c. 50 cm of water in small lake, La Cumbre, 16 km N of the puesto de transito Chuquiaguillo, vicinity of the laguna Estrellani, Murillo Province, 4600 m, 24 August 1986, J.C. Solomon 15520 (G). CHILE. LOS RÍOS: In provincia Valdivia, s.d., R.F. Hohenacker 1402 (G); in paludosus circa urbam Valdivia, November 1853, Lechler 1402 (K); MAGALLANES. Slow running stream, extremely cold water, road to Punta Arenas, ca. 50 km southwest of Puerto Natales, 30 m, W.J. Eyerdam et al. 24187 (K). COLOMBIA. 27 August 1948, J.A. Molina & F.A. Barkley 18S701 (BM). SANTANDER: Submerged in shallow pool in open páramo, Páramo Rico, 5 km s of California, 7º 18’ N, 72º 57’ W, 3750 m, 15 September 1944, H. St. John 20762 ( US); En suelos humedos y poco humedos, en el paramo de Santurban, 3600 m, 27 August 1948, J. Araque & F.A. Barkley 18S701 ( US). ECUADOR. CHIMBORAZO: Small tarn in páramo, Urbina. towards Mt. Chimborazo, 3750 m., 24 July 1939, E. Asplund 7790 (F). URUGUAY. DURAZNO: In aqua fluent., laterite, Blanquillo, 150 m, September 1947, G. Herter 9724 (NY). VENEZUELA. MÉRIDA: In running water, small streams in quebradas (Ravines) draining to lake in basin between drier slopes dominated by Espeltia, Sierra de Sto. Domingo, Paramo de Mucubají, alrededores de La Laguna Grande, 19 November 1959, H.G. Barclay & P. Juajibioy 9590 ( US); in shallow, algae-filled water of the seepage outlet of a small laguna with floating Ranunculus , E. moraine along Laguna Macubají, 3600 m, 17 August 1972, L. Loveless 1856 (F).

Figures

FIGURE 1. Fruits of South American Callitriche: a—C. albomarginata, b—C. antarctica, c—C. berteroana, d—C. ciliata, e—C. ciliata showing fibrils, f—C. concinna, g—C. dacryoidea, h—C. deflexa, i—C. ecarinata, j—C. hegelmaieriana, k—C. heterophylla, l—C. heteropoda.

FIGURE 3. Epitype of Callitriche antarctica (R.C. Winkworth & F. Hennion 42, P barcode P02432590). Copyright: Muséum National d’Histoire Naturelle.