Oxalis benjaminii Lourteig (2000: 308)

Nuernberg-Silva, Anelise & Fiaschi, Pedro, 2021, Taxonomic revision and morphological delimitation of Oxalis sect. Ripariae (Oxalidaceae), Phytotaxa 529 (1), pp. 125-159 : 133-134

1. Oxalis benjaminii Lourteig (2000: 308) .

Type (lectotype designated here):— PARAGUAY. Caaguazú: dans les campos, 12 November 1874, B.Balansa 2242 ( P02440123 !, image of the lectotype available at https://science.mnhn.fr/institution/mnhn/collection/p/item/ p02440123; isolectotypes at BR0000005286904 !, G fide Lourteig, GOET fide Lourteig, K fide Lourteig, P02440124 !, P02440125 !, SR8311 !) (figs. 5–6).

Decumbent subshrub. Stem slender, up to ca. 60 cm long, branching from the base, decumbent, densely covered with leaves; shorter hairs ca. 0.4 mm long, curved or appressed, very abundant; longer hairs ca. 1 mm long, ascending and patent, abundant; glandular hairs ca. 0.5 mm long, sparse; internodes 0.4–1.3 cm long. Stipules ca. 1.1 × 2 mm, semicircular, the apex connate to the petiole, hairs like on stem; petioles 2.2–9.5 cm long, pulvina ca. 1 mm long. Leaf blades 7–18 × 4–13 mm, coriaceous, widely obovate to obovate, discolorous, with base cuneate, margin revolute, apex truncate to rounded, sometimes mucronulate; shorter hairs ca. 0.4 mm long, curved or appressed, abundant adaxially, very abundant abaxially; longer hairs 1–2 mm long, ascending and patent, moderate adaxially, abundant abaxially; glandular hairs ca. 0.5 mm long, occasional adaxially, sparse abaxially. Dichasia with 5 flowers, as long as the leaves; peduncle 1.5–6.1 cm long; bracts 1–2.5 × 0.2 mm, lanceolate; shorter hairs ca. 0.2 mm long, ascending, abundant; longer hairs ca. 1 mm long, patent, moderate, reddish; bracts 1–2.5 × ca. 0.2 mm, lanceolate; bracteoles ca. 1.1 × 0.2 mm, lanceolate. Pedicels 5–8 mm long; sepals 4–5.5 × 0.75–1 mm, base rounded, apex acute, hairs ca. 1 mm long, ascending, simple and glandular, very abundant; petals yellow, 6.6–8 mm long, spatulate, with apex crenatedenticulate, adaxially with glandular hairs; the shorter stamens ca. 2 mm long, glabrous, the longer ones ca. 4 mm long, hairs ascending; mid-styled pistil, ca. 5 mm long, with abundant, ascending hairs, stigmas papillose. Capsules 2.6–4 × 4.7–5.7 mm, depressed ovoid, 5-lobed, hairs ca. 2 mm long, patent, very abundant. Seeds 1 per locule, ca. 2 × 1.5 mm (immature), widely elliptic to elliptic, with rounded base and acute apex.

Distribution and habitat: —Endemic to Paraguay and known only for the municipality of Caaguazú (Caaguazú Departament), and near Pira Pytá river (Alto Paraná Departament) (fig. 6). It grows in grasslands and in the margin of seasonally dry forests.

Phenology: —Flowers and fruits have been collected in September and October.

Conservation status: — The only record of this species at Caaguazú Department dates 12 November 1874. Between 1989 and 1990, Oxalis benjaminii was found about 150 km far from this locality, in Alto Paraná. The species has not been recorded in protected areas and the only known records are from areas of extensive agriculture and cattle farming, including the type-locality, which has suffered deforestation since 1970 and is now an urban area. The AOO of this species is 8 km ², with an inferred decline in extent and habitat quality, thus recommended as Critically Endangered ( CR) applying the criterion B2 a,b(iii) .

Typification of Oxalis benjaminii : — Lourteig (2000) described Oxalis benjaminii citing six specimens of Balansa 2242 [ BR, G, GOET, K, P (2 specimens)]. Between the two specimens at P, she indicated one as the “ holotype ” and the other as an “isotype”, but she did not provide any means to distinguish these two specimens, so they are regarded as syntypes (cf. Art. 40.2 of ICN). We located three samples of B. Balansa 2242 at P (barcodes P02440123 , P02440124 , and P02440125 ), all of which were identified by Lourteig. Among these, the material selected as the lectotype ( P02440123 ) is the one with fruits and floral remains, and which best represents its habit, with more spacely arranged leaves .

Taxonomic notes: —This species can be easily recognized by small obovate to widely obovate and strongly discolorous leaflets, with a whitish abaxial surface due to dense hair-covering. Leaves have an helicoidal arrangement and leaflets are caducous, leaving persistent petioles. It is morphologically similar to Oxalis paranaensis , from which it can be distinguished by the decumbent stem, branching from the base (vs. procumbent, non-branched stems in O. paranaensis ), and the 2–5-flowered (vs. 1–3-flowered) inflorescences. Moreover, the river basin where Oxalis benjaminii occurs drains to Paraná river, and is about 700 km away from the locality where O. paranaensis is found, which drains to the Iguaçu river.

Specimens examined: — PARAGUAY. Alto Paraná: Zona rio Pira Pyta , 20 September 1989, G. C . Marmoni 1611 ( CTES); Estancia Santa Elena , 11 October 1990, A . Schinini & G. C . Marmori 27218 ( CTES, FLOR, P) .