Indigofera stolonifera, São-Paulo, Rita De Cássia Alves Menezes, Snak, Cristiane, Ribeiro, Carolina Lima, Rocha, Lamarck & Queiroz, Luciano Paganucci De, 2025

São-Paulo, Rita De Cássia Alves Menezes, Snak, Cristiane, Ribeiro, Carolina Lima, Rocha, Lamarck & Queiroz, Luciano Paganucci De, 2025, A new species of Indigofera (Leguminosae, Papilionoideae) from Misiones with a key to species from Argentina, Phytotaxa 690 (2), pp. 293-300 : 294-297

Indigofera stolonifera R.C. São Paulo & L.P.Queiroz, sp. nov. ( Figures 1 , 2 ).

Type: — ARGENTINA. Misiones: San Javier, Paraje Mandarina, 27°52’42.40”S, 55°17’5.60”W, fl., 9 October 2020, H. A. Keller et al. 14138 (holotype: CTES [0066192]!).

Indigofera stolonifera is morphologically similar to Indigofera campestris Bongard ex Bentham (1839: 38) , by inflorescences 8–10 cm long and flowers with salmon to orange petals, but differs in habit ( I. stolonifera is an erect stoloniferous herb, whereas I. campestris is a prostrate or decumbent subshrub), shorter petioles (2–2.5 mm long vs. 5–6 mm long) and in leaflet indumentum (sericeous to velutinous vs. pubescent).

Description:— Erect herb, ca. 15 cm tall, with stolons; branches with determinate growth, ca. 8 cm long, green, striated; indumentum sericeous to velutinous, whitish on the branches, stipules, petiole, rachis, leaflets, and inflorescence. Stipules 4–4.5 × 1.3–1.5 mm, triangular. Leaves ca. 2 × 3 cm, imparipinnate; petiole 2–2.5 mm long, striated; rachis 9–11 mm long, interfoliolar segment 2–3 mm long; petiolules ca. 1 mm long, with reddish colleters on the petiolule of the terminal leaflet; leaflets 3–5, alternate, conduplicate, and slightly succulent, oblong to obovate; apex rounded, mucronate; base rounded; margins entire; adaxial surface silky; abaxial surface velutinous; basal leaflets 6–6.5 × 4–4.5 mm, median leaflets 5–6 × 4–5 mm, distal leaflet 7–7.5 × 6–6.5 mm. Raceme 8–10 cm long, axillary, erect; peduncle 5–6 cm long, densely flowered; bracts 1.8–2 × 0.6–0.8 mm, triangular, sericeous, deciduous; pedicel 1.2–1.5 mm long, velutinous. Flowers 7–8 mm long; calyx campanulate, 5-laciniate, calyx tube 0.8–1.2 mm long; lacinia 2–3 × 0.5–0.6 mm, subequal, subulate to triangular; petals salmon to orange; standard petal 7–8 × 5–5.5 mm, glabrous, obovate, apex rounded and mucronate, base attenuate, claw 0.5–0.6 mm long; wing petals 7.8–8 × 2–2.5 mm, glabrous, obtrullate, apex cuneate to obtuse, base asymmetrically hastate, claw 0.6–0.7 mm long, adhered to the keel; keel petals 7.2–7.5 × 1.8–2 mm, glabrous, united along the external margin from the apex to the median region, with hollow spurs in the median region, obtrullate, apex cuneate to acute, base attenuate, claw 0.3–0.4 mm long; androecium diadelphous (9 stamens joined in a sheath and the vexillary one free), stamens 5–5.5 mm long, anthers ca. 1 × 0.5 mm, oblate, apiculate; ovary 4–4.3 × 1–1.2 mm, sessile, slightly curved at the apex, ciliate at the apex, 12-ovulate; style 1.2–1.5 mm long, curved, glabrous; stigma capitate, with a small terminal pore. Fruit and seeds are not observed.

Etymology: —The specific epithet is derived from the Latin “stolon” referring to the elongated branches produced by the plant, which grow parallel to the ground and give rise to new individuals.

Phenology: —The presence of flowers was observed in the month of October.

Distribution and habitat:— Indigofera stolonifera is known only one collection from Misiones province, northeastern Argentina ( Figure 3 ), in the Paranaense phytogeographic region ( Cabrera 1976). The new species grows in latosol-type soil, where grasses and herbaceous plants predominate ( Velazco et al. 2018).

Conservation status:— As the new species is known from only one locality, it was not possible to calculate its Extent of Occurrence (EOO) or Area of Occupancy (AOO) using the IUCN B criteria. Attempts to re-sample the species were unsuccessful due to the complete destruction of its habitat by human activities. As a result, it was not possible to estimate the population size, as the habitat had been altered and the natural vegetation removed, preventing the collection of the species. Although the species occurs near Iguazú National Park, the area is unprotected and subject to ecological pressures, including habitat degradation caused by logging, cattle grazing, the invasion of exotic species (pine trees), and yerba mate cultivation. Given the lack of data on population size and the threats to its habitat, we propose the category DD (Data Deficient) for this species.

Notes: — Indigofera stolonifera is the first South American species of the genus documented to possess stolons (e.g. Burkart 1942; Rodas 1991; Lievens 1992). Another distinctive feature is the juvenile appearance of leaves, that remain partially conduplicate, giving the impression of being incompletely expanded.

The new species is morphologically most similar to Indigofera campestris , sharing salmon to orange petals and inflorescences 8–10 cm long. However, I. stolonifera is distinguished by its stoloniferous habit, with remote, erect branches, compared to the prostrate or decumbent subshrub habit of I. campestris , which lacks stolons. The stipules of I. stolonifera are shorter (4–4.5 mm long) than those of I. campestris (7–7.5 mm long). The leaflets of I. stolonifera are densely covered with sericeous to velutinous indumentum, whereas those of I. campestris are pubescent. Additionally, I. stolonifera exhibits glabrous petals, a feature that contrasts with the strigose petals of I. campestris .

Indigofera stolonifera also shows resemblance to I. parodiana Burkart (1941: 57) in leaf size, with leaves 2–3 cm long and alternate leaflets. However, I. stolonifera is distinguished by its sericeous to velutinous branches and longer inflorescences (8–10 cm long) that exceed the length of the adjacent leaf. In contrast, I. parodiana is characterized by strigose branches and inflorescences 2–3 cm long, which are equal in length to the adjacent leaf. Other differences between the new species and the most similar species are presented in Table 1.

Indigofera stolonifera is further distinguished from other South American species of the genus by its larger anthers (ca. 1 mm long vs. 0.4–0.5 mm in other species). The only South American species with similarly large anthers is Indigofera blanchetiana Bentham (1859: 40 , native to the Caatinga biome in northeastern Brazil. However, I. blanchetiana is readily differentiated from I. stolonifera by its shrubby habit, reaching up to 1.5 m tall, and its opposite leaflets, which number 9 to 15 ( Lievens 1992).

Until now, nine species of Indigofera were recorded for Argentina (Burkart 1942), from which only four reported for the province of Misiones [ I. asperifolia Bong. ex Bentham (1839: 431) , I. bongardiana (Kuntze) Burkart (1942: 171) , I. latifolia Micheli (1883:13) , and I. suffruticosa )] (e.g., Zanotti et al. 2020). Even after an extensive review of herbarium collections, none of these species proved to be morphologically equivalent to the new species. Consequently, this study increases the number of Indigofera species recorded in Argentina to 10 and raises the number of species in Misiones to five.

Figures

FIGURE 1. Indigofera stolonifera R.C. São Paulo & L.P. Queiroz.A. Flowering branch. B. Bract C. Calyx. D. Standard petal. E. Wing petal. F. Keel petals. G. Androecium. H. Gynoecium. Drawn by K. A. Soares.

FIGURE 2. Indigofera stolonifera R.C. São Paulo & L.P. Queiroz.A. Environment where the plant is found. B. Branch. C. Habit and the arrow indicates the stolon. D. Inflorescences. Photographs: A. C. L. Ribeiro e B–D, by K. H. Alejandro.

FIGURE 3. Geographical distribution of Indigofera stolonifera in the province of Misiones, Argentina.