Ranunculus oblitus G. Wiegleb, M. Desfayes et A. A. Bobrov, 2022

Wiegleb, Gerhard, Desfayes, Michel & Bobrov, Alexander A., 2022, Ranunculus oblitus (section Batrachium, Ranunculaceae), a new species from South America, Phytotaxa 559 (2), pp. 132-144 : 136-141

Ranunculus oblitus G. Wiegleb, M. Desfayes et A. A. Bobrov , sp. nov.

Type. Argentina. Santa Cruz , Lago San Martín, in lacusculo, c. 600 m s.m, 09.III.1905, P . Dusén s.n. (holotype, HBG [HBG-526025]! ( Fig. 2 ); isotypes, BA, BAF, K!, S06-7195 !) .

Diagnosis. Ranunculus oblitus is characterized by the combination of the small size, the reddish color of the stem and laminar leaves (in fresh state), the 3-5 lobed laminar leaves, the low number of terminal segments in capillary leaves (<30), the short sepals (<2 mm), the circular to elongated nectar pits, the low number (<20) of glabrous achenes, and the hairy receptacle.

Description. Annual or wintergreen perennial hydrophyte; aquatic state prostrate or erect, with capillary and laminar leaves (batrachid); terrestrial state prostrate, creeping, with rigid fleshy capillary leaves. Shoots up to 20 cm long, (1‒)2.0‒ 2.5 mm in diameter, with a brownish or reddish tinge, glabrous, rooting at all nodes; internodes 20‒30 mm long, approximately equally long as the adjacent leaf. Laminar leaves present or absent, alternate, (6‒) 10‒18 mm wide, glabrous, often with a reddish tinge, with 3(‒5) primary lobes, dissected to less than 1/2 of the lamina, margin of secondary lobes dentate or crenate in 3-lobed leaves, entire and rounded in 5-lobed leaves; petioles 10‒23(‒40) mm long. Intermediate leaves sometimes present, alternate, with 2‒3 cuneate, deeply divided main lobes, with 3‒4- dentate secondary lobes. Capillary leaves present, alternate, 10‒30 mm long, flaccid, rarely rigid (after regrowth from terrestrial state), glabrous, number of terminal segments 20‒30; petioles (5‒) 10‒15 mm long, slightly longer in the lower part. Stipules ca. 2/3‒3/4 adnate to petiole, free portion convex, glabrous or sparsely hairy. Pedicels 7‒20(‒30) mm long, opposite to laminar or capillary leaves, 0.8‒1.2 mm wide, mostly recurved, glabrous. Sepals 5, 1‒2 mm long, blue-tipped, reflexed. Petals 5‒6(‒8), 2‒4.5(‒5.5) mm long, spathulate to ellipsoid, obtuse, white with small yellow claw, not contiguous in anthesis. Nectar pits 1 per petal, circular or elongated. Stamens 10‒15. Carpels 10‒20, 1.5‒1.8 mm long, with scattered dorsal hairs, glabrous at maturity, style short, caducous. Receptacle globose, not elongating in fruit, puberulent to pubescent. Chromosome number unknown.

Icons. Drawings of the species are found in Lourteig (1951, p. 451, Fig. 14, based on a specimen of the type collection); and Ruiz (2001, p. 65, lamina 10g, h). Photographs are found in Lumbreras et al. (2014, p. 24, Fig. 2d ); Marijn van den Brink’s photos (2021, Argentina Marijn-0068); Kok van Herk photo database (2021, Argentina Pa 2599). The photographs by M. van den Brink and K. van Herk are reproduced in this paper as Fig. 3 and Fig. 4 , respectively.

Etymology. The epithet “ oblitus ” is derived from the Latin verb “ oblivisci” and means “forgotten” or “ignored”.

Nomenclature. The newly described species was never considered a separate species before the collections of M. Desfayes in 2001 (annotated as ‘ Ranunculus “ aquatilis ” auct.’ and ‘ Ranunculus, 2001 ’, in G). It has been overlooked or confused for such a long time. Originally, all plants were assigned to R. aquatilis due to the occasional presence of laminar leaves ( Reiche 1894, Spegazzini 1896). This was largely accepted both in taxonomic ( Cook 1966, Ruiz 2001) and phytosociological works (e.g., San Martín et al. 2011, Urrutia Contreras 2016).Also, the name R. trichophyllus was used instead (e.g., Lourteig 1951, Raynal-Roques 1992, Flora de la Argentina 2018, INTA 2021, Teillier 2021). Both species were recognized by Lumbreras et al. (2014). They used the name “ R. aquatilis ” roughly in the circumscription of the new taxon in present paper. The new species has been wrongly associated with North American R. mongolicus by Wiegleb et al. (2017). All available synonyms are informal names or misapplications. The usage of names such as “ R. aquatilis auct. non L.” ( Zuloaga & Morone 1999, INTA 2021) and “ R. aquatilis auct. div. argent. non L.” ( Lourteig 1984: 320, pro syn.) did not imply that the respective authors had an undescribed species in mind but assumed identity with R. trichophyllus instead.

Distribution and habitat. Batrachium populations have been found in South America in the southern ranges of the Andean Region, extending over a total distance of ca. 5000 km ( Fig. 5 ). A list of additional specimens examined (paratypes) is given below.The northernmost region comprises the pre-Andean mountains around Lima ( Peru). Laminarleaved plants are missing in Peru and none of the populations matches the description of R. oblitus . Submerged plants from Peru belong to another species (see below). Such plants also occur further southward, partly in the same regions as R. oblitus populations.

The known range of Ranunculus oblitus is divided into three parts. Northernmost sites are situated in the high mountain region around Lake Titicaca ( Bolivia: Prov. La Paz and Prov. Oruro). There seems to be a gap in the northern regions of Chile. The central sites include the temperate regions in central Chile of Región V (Valparaiso) to X (Los Lagos) including RM, the newly formed regions XIV and XVI as well as the off-the-coast island of Mocha. Adjacent occurrences are found in the Argentinian provinces Neuquén and Chubut where high elevations are reached. R. oblitus may as well occur in between (provinces San Juan, Mendoza, and Río Negro) but may have been overlooked (see INTA 2021). Another gap exists in the Chilean Región XI (Aisén) and adjacent Argentinian provinces. San Martín’s et al. (2010) record of “ R. aquatilis ” applies to this region, but no comprehensible description is given. Southern sites are situated in the subarctic region of southern Patagonia and Tierra del Fuego in Chile (Región XII Magallanes y Antártica Chilena) and Argentina (prov. Santa Cruz, prov. Tierra del Fuego).

Little is known about the ecology of R. oblitus . It has been reported from ponds, ditches, small streams, wetland marshes and lake margins from sea level to ca. 300 m above sea level in southern Chile and Argentina, from sea level to 4300 m above sea level in central Chile and Argentina, and from 3000 to 4500 m above sea level around Lake Titicaca. Climatic conditions are described as either cold-temperate to subarctic ( Lumbreras et al. 2014) or dry highalpine ( Raynal-Roques 1992). Humid climatic conditions seem to allow the formation of large stands of amphibious and terrestrial forms on organic substrate. Populations from central Chile and Argentina are more often found fully submerged producing less laminar leaves, which may explain that such forms were not reported by Lumbreras et al. (2014). Aquatic habitats are mostly oligotrophic. No specific preference for acid or calcareous water was found ( Lumbreras et al. 2014). Occurrence near the seashore and in semiarid Alpine regions may suggest tolerance to slightly brackish conditions. Taken together, the species seems to be rare but not endangered. It mostly colonizes remote undisturbed habitats.

Status and phytogeography. The new species is native to South America. It may have arisen in the past from an introduced North American taxon by genetic drift (founder effect) and subsequent rapid adaptation to the different environment. The range divided into three parts suggests that the species had a wider distribution in the past. A hybrid origin can be excluded due to normal fertility of studied plants and absence of additive polymorphism pattern at the ITS sequences. Rapid evolution of a new hybrid species would require that potentially interbreeding species be getting in contact after earlier isolation. This was assumed for species of the R. penicillatus complex having evolved within the past 250 years ( Wiegleb 2020). Other new Batrachium species of hybrid origin such as North European R. schmalhausenii Luferov (1997: 57) and East Asian R. nipponicus have evolved in regions which became simultaneously colonizable for a variety of species after the last glaciation ( Bobrov et al. 2015, Wiegleb et al. 2017).

A close relationship between South and North American terrestrial Ranunculus species was found by Emadzade et al. (2011). The resulting “North-South American Amphitropical Disjunction” is a common pattern in American phytogeography ( Wen & Ickert-Bond 2009). The pattern is usually explained by past long-range seed transport by birds. All known sites of the new species R. oblitus lie along the Pacific American bird flyway ( EAAFP 2021). However, it cannot be introduced in recent times, as morphological differences to all potential source taxa are too large. Unintentional introduction suggested by Lumbreras et al. (2014), e.g., by ballast water, is highly unlikely as the first Batrachium specimens have already been collected in 1828 by C. Bertero ( Lourteig 1951).

Additional specimens of Ranunculus oblitus examined (paratypes). BOLIVIA. La Paz. Achacachi, [16°03’28.90”S 68°40’45.07”W], 3850 m (near Lake Titicaca ), in a small stream, 10.X.2001, M . Desfayes s.n. (G-040110, duplicate in LMO-BOT8389!, duplicate in WELT-SP100372 ); La Paz, Prov. Murillo, Paso Las Animas , ca. 5 km east of CalaCota (sic!, = Cala Coto , La Paz ), Laguna Las Animas , 24.XI.1984, J. C . Solomon 12878 ( MO) .

CHILE. Región VII. Prov. Concepción, Laguna rotunda (sic! = Laguna redonda), 13. I .2004, M . Desfayes (G-040113, LMO-BOT8387); Isla Mocha, Westseite , in Lagune , undated, G . Kunkel 1737 ( B); Región IX. Temuco: Iliga, 10 m, 20.XII.1934, A . Garaventa s.n. ( CONC!); Sierra de las Baguales, Cerro Santa Lucía , M . Arroyo s.n. ( SGO); Región X. Prov. Valdivia, Trumao, Vega del Río Bueno Amarillo 73/74° 40/41°, 8 m, 20.XII.1932, A . Hollermayer 640, Herb. Aellen ( B, G-074233); Prov. Llanquihue, Lago de Todos Santos , II-III.1911, L . L . Hauman 241 ( B); Región XII. Prov. Magallanes, Salto Grande del Payne , 24.XII.1969, E . Pisano 2376 ( CONC, MO!); Punta Arenas [Sandy Point], 07.II.1867, R . O . Cunningham s.n. ( K!); Punta Arenas, Port Famine , 5. I .1869, R . O . Cunningham 1866-69 ( K!); Punta Arenas, 11. I .1951, H . Pfister s.n. ( CONC); Punta Arenas, 09. I .1951, C . Cekalović ( CONC!); Rio Guai [y]rabo, 06.II.1971, E . Pisano 2924 ( MO!); Canal Beagle, I .1920, M. Gusinde (E-203, duplicate in WU); abundant in a shallow pool on the east side of route 9, ca 60 km north of Punta Arenas , [52°40’18”S 71°05’53”W], 75 m, 31. I .2001, M . Desfayes (G-010131.15!, duplicate in LMO-BOT8390!: Puerto Natales, pond near sea level, 30. I.2001); 15 km south of Punta Arenas , shallow water of stream, 06. I .1939, Eyerdam, Beetle, Grondona 24154 ( MO); Punta Arenas, I .1902, K. Wolffhügel ( G!); Prov. Tierra del Fuego, Altos de Boquergon , 9 km E of Porvenir, [53°18” S 70°12’W], by small lake, 14.XII.1971, D. M . Moore , R. N . Goodall 81 ( K!). Unknown part of Chile. Herbarium Chilense, purchased of Mr. E . C . Reed , XII.1873 ( K!) .

ARGENTINA. Prov. Neuquén. Parque Nacional Lanín, Lago Ruca Choroi SW, 30.I.1968, Eskuche, Klein (G-1383-3!); Prov. Santa Cruz. Patagonia australis, Rio Fósiles, in lacusсulo, c. 800 m s.m, III.1905, P. Dusén (K!) (see type!); Lago Buenos Aires, 250 m, VI.1941, Eyerdam, Beetle, Grondona (G!); Estancia Cerro Fitz Roy, Río de la Vueltas, 420 m, 26.XII.1950, H. Stemmer (G-7343!); Near Loma del Pliegue tumbado, Los Glaciares, El Chaltén, Cerro Fitz Roy (high resolution images, van den Brink 2021, 3.XII.2014, van Herk 2021); Prov. Tierra del Fuego, Antártida e Islas del Atlántico Sur. Lago Fagnano, Cabezera, Lago at the E end of Lago Fagnano, in a little lake close to Lago Fagnano, 30.III.1940, R. Santesson 704 (K!); Ushuaia, La Peninsula, in a small lake, 01.XI.1940, R. Santesson 375 (K!); Ushuaia, 23.XII.1949, en un turbal, Hunziker (Z); Estancia Remolino, NW of settlement, stream above house, 54°50’S, 67°52’W, 22.II.1968, D. M. Moore 2002 (K!).

Figures

FIGURE 2. Holotype of Ranunculus oblitus (coll. P. Dusén), reproduced with permission of Herbarium Hamburgense (HBG).

FIGURE 3. Photograph of the laminar-leaved form of R. oblitus from Argentina, Prov. Santa Cruz, 3 Dec 2014 [Marijn van den Brink 0068], reproduced with permission of the author.

FIGURE 4. Field photograph of Ranunculus oblitus, Detail of flowers, from Argentina, Prov. Santa Cruz [Kok van Herk, no. Pa 2599], reproduced with permission of the author.

FIGURE 5. Distribution of areas with Ranunculus oblitus (black dots). The areas also contain unresolved Batrachium specimens. The open circles indicate areas where only non-laminar leaved Batrachium specimens have been found (map base: https://de.wikipedia.org/ wiki/Datei:South_America_laea_location_map.svg).