Portulaca ragonesei D. Legrand (1949: 333

Cantero, Juan Jose, Barboza, Gloria E. & Ocampo, Gilberto, 2017, Rediscovery of a halophytic endemic and rare species of Portulaca (Portulacaceae) from central Argentina: morphology and its phylogenetic position, Phytotaxa 332 (1), pp. 41-50 : 43-47

Portulaca ragonesei D. Legrand (1949: 333 , tab. 2).

Type:— ARGENTINA. “ Córdoba: El Tuscal, Salinas Grandes, 28 April 1948, Ragonese s.n. ( A. 69511) (holotype MVM!, isotype CORD 00002591!) ( Figs. 2 , and 3).

Improved description:— Herbs perennial, succulent, glabrous, ca. 40 cm long. Taproot thick, light to dark brown, 6–12 cm long, from which other roots sprout laterally. Stems reddish purple to pink, prostate to ascending, simple or few branched, up to 50 cm long × 0.2 – 0.5 cm diam. Leaves usually alternate, subopposite at the apex, linear, terete, fleshy, shiny, white greenish, sometimes red-tinged, (0.7–)1.5 – 4.8(–5.5) × 0.2 – 0.5 cm, base prolonged as a spurlike ca. 2 mm, apex rounded, glabrous, subssesile, petiole 0.2–0.3 mm; axillary hairs absent. Inflorescence a sessile terminal head, (1–)2 – 4(–7)-flowered, subtended by a whorl of 3 – 5 leaves. Buds red-lead, ca. 18 mm, subtended by small fleshy ovate-acuminate whitish bracts with green a midrib, ca. 3.6 mm; flowers 3.5 – 4 cm diam, short-pedicellate, pedicels 5 – 7 mm; sepals 2, fleshy, subequal, keeled, greenish, 0.8 – 1.1 × 0.5 – 0.8 cm, the larger one widely ovate, retuse at apex, with a hyaline margin 2 – 3 mm wide, the shorter one ovate-lanceolate, shortly apiculate, and with a scarcely hyaline margin; petals 5, quincuncial, dark yellow to orange-yellowish with a reddish spot in the adaxial surface at the base, triangular-ovate to ovate, emarginate, notch 0.3 – 0.5 cm deep, base unguiculate, 2.3 – 2.8 × 2.3 – 2.5 cm; stamens 50, filaments 5–8 mm, white at the base becoming reddish purple towards the apex, glabrous; anthers ca. 1 mm long, reddish purple, thecae parallel; gynoecium 18 – 21 mm long, ovary ovoid, 2 mm long, many-ovulated, style exerted beyond the stamens, white, 13 – 15 mm long, stigma white, 5-lobed (rarely 4 - lobed), the lobes oblonglanceolate 2 – 4 mm long, the stigmatic surfaces with long hairs, ca. 0.3 mm. Capsule (pixidium) circumscissile, light brown, base conspicuously dark, brown nerved, ca. 4.5 – 5.0 mm alt., multiseminate, long pedicellate, dehiscence line close to the base, operculum fusiform with vestigial corolla with age, and with a constriction at its apex forming a cell where one seed is placed, pericarp thin; fruiting pedicel curved upward, costate, 3 – 4(–5) mm. Seeds dark brown, shiny, subreniform, ca. 1.5 mm in diameter, individual cells elongated, anticlinal walls undulate with U-type pattern, periclinal walls par-convex, par-conical.

Distribution and habitat:— Portulaca ragonesei is an extreme halophyte endemic from central Argentina, inhabiting the southern side of Salinas of Ambargasta (Province of Córdoba, Department of Tulumba, Fig. 1 ), at ca. 140 m a.s.l. It is found in saline dry mudflats, where is locally abundant in the Allenrolfea + Salicornia + Heterostachys bushland community that remains without a formal syntaxonomic level ( Martínez Carretero et al. 2016). Typically, it spreads over the basal stratum of the community as prostrate-ascendent succulent herb among basal branches of bushes ( Fig. 1B ); in this patchy environment, P. ragonesei inhabits small sediment micro-domes where is less affected by floodings.

Phenology:— Portulaca ragonesei is a geophyte sprouting from a tap root system every year at beginning of spring, after the first rains. The species flowers in December. Flowers open at sunset for not more than four hours. Fruits are found from January to May. Aerial parts die with first frozen days at fall, but the tap root system is persistent throughout the life of the plant.

Notes on the holotype:— When the Uruguayan Diego Legrand described this species, he designed the holotype (A. 69511) referring it to Laboratorio de Botánica, Ministerio de Agricultura de Buenos Aires (today BAB herbarium). Probably, he asked on loan specimens from different herbaria and he had at hand the specimen A. 69511 from BAB. After that, this specimen never came back to Argentina and so, it remains currently housed at MVM.

Conservation status:— Portulaca ragonesei is currently known only from one site, and the observed population has less than 250 individuals. Therefore, it should be considered as a very small or restricted population and we propose to assess it as Critically Endangered (IUCN 2014). The area of occupancy is calculated to be less than 10 km 2 (Criterion B2a) and the species was again collected in the surroundings of the original site of the holotype after 67 years.

Additional specimens examined:— ARGENTINA. Córdoba, Tulumba, La Costa, ca. 4 km del desvío hacia el noroeste desde la ruta hacia El Tuscal, 29º43 ′ 59.5 ′′ ; 64º33 ′ 24 ′, 138 m a.s.l., 15 May 2015, Barboza et al. 4400 ( CORD00086497 !) ; Salinas de Ambargasta , en la propia salina y los alrededores de la Costa, 29°43 ′ 50.3 ′′ S, 64°33 ′ 32,7 ′′ W, 140 m a.s.l., 7 December 2016, Barboza et al. 4601 ( CORD00056275 ) .

Figures

FIGURE 1. Distribution map of Portulaca ragonesei. A. Cuenca Saliniana (Córdoba, Argentina). B. Halophytic bushland in Salina of Ambargasta. C. Habit of P. ragonesei.

FIGURE 2. Morphology of Portulaca ragonesei. A. Taproot; B. Leaves; C. Buds; D. Flower, lateral view; E. Flower showing calyx; F. Flower, longitudinal section; G. Flower, upper view; H. Fruit; I. Post-dehiscent fruits. J. Seed.