Plantago pretoana ( Rahn 1964: 51–53 ) Hassemer 2015

Hassemer, Gustavo, Trevisan, Rafael, Meudt, Heidi M. & Rønsted, Nina, 2015, Taxonomic novelties in Plantago section Virginica (Plantaginaceae) and an updated identification key, Phytotaxa 221 (3), pp. 226-246 : 232

Plantago pretoana ( Rahn 1964: 51–53) Hassemer , comb. et stat. nov.

≡ P. australis subsp. pretoana Rahn (1964: 51–53) . Type:— BRAZIL. MINAS GERAIS: Itatiaia, an Tijuca près de la source du Rio Preto, 20 November 1876, A.F.M. Glaziou 8897 (holotype C!, isotypes LE and R, photographs!).

Rosette herbs, 10–58 cm tall, perennial, becoming black, or almost so, on drying. Taproot absent; caudex a rhizome, 1–10 × 0.5–1.8 cm, usually with brownish orange trichomes. Leaves narrowly-elliptic or narrowly-ovate, 7–40 × 0.6–3.0 cm, 3- to 7-veined, membranaceous; petiole scarcely distinct; lamina quite glabrous on both faces or rarely with scattered, patent, type G trichomes, 0.2 mm long; margin with usually inconspicuous teeth, glabrous or rarely with short cilia 0.1 mm long; apex acuminate. Inflorescence 14–58 cm long. Scape 10–44 cm long, cylindrical, generally with longitudinal grooves and trichomes 0.8–1.3 mm long, type G, sparsely-distributed, appressed and antrorse. Spike 4–14 cm long, shorter to subequal to the length of the scape, cylindrical, multi-flowered, with flowers densely packed above, less densely crowded below. Bracts ovate to narrowly ovate, 1.7–2.0 × 0.3–1.8 mm, glabrous to glabrescent. Anterior sepals elliptic, 1.9–3.5 × 0.8–1.4 mm, wholly glabrous; apex acute. Posterior sepals ovate, 2.0–3.0 × 1.1–1.5 mm, wholly glabrous; apex acute. Corolla actinomorphic, glabrous; lobes ovate, 1.9–2.5 × 1.2–1.6 mm, shorter than the sepals, patent, glabrous; apex obtuse to acuminate. Stamens 4. Ovary with 3 ovules, sometimes malformed and with only 1–2 ovules; pyxidium 2.5–3.0 × 1.4–1.7 mm, 3-seeded, sometimes bearing only one malformed seed. Seeds ovoid, flattened to slightly concave ventrally, convex dorsally, 1.5–2.0 × 1.0– 1.3 mm; surface reticulate, black.

Illustration: — Figure 2 .

Phenology: —Flowering June–March, fruiting December–March.

Habitat and distribution: —Known only from two very restricted, considerably disjunct areas: high-elevation rocky bogs at 2100–2500 m asl in Serra do Itatiaia, southeastern Brazil, and wet grasslands around Lagoa Dourada, 790–840 m asl, in Parque Estadual de Vila Velha, Ponta Grossa, Paraná state, southern Brazil ( Figure 3 ).

Conservation status: —Endangered (EN–B2a,b[iii]). Plantago pretoana is a very rare and restricted species, being known from only two markedly disjunct areas. The only two collections of this species from Lagoa Dourada are from 1914 and 1978; recent (January 2015) collection efforts around Lagoa Dourada by GH were unsuccessful. It is possible that the population of P. pretoana around Lagoa Dourada may be in decline due to habitat loss, as the grasslands there are gradually being substituted by shrubby vegetation, notably by the advance of Mimosa pigra von Linné (1755: 13–14) ( Fabaceae ), a notoriously problematic invasive plant species ( Braithwaite et al. 1989). The protection of southern Brazil grasslands is an urgent matter that needs to be discussed widely among scientists and Brazilian politicians, due to the increasing loss of biodiversity in these habitats.

Discussion: — Plantago pretoana was described by Rahn (1964) as a subspecies of P. australis , together with other species and subspecies in section Virginica with wide, antrorse trichomes on the scape. Later, in his treatise on the section Virginica, Rahn (1974) adopted a narrower circumscription for P. australis , including only plants without a taproot, which resulted in his acceptance of P. buchtienii Pilger (1913: 251–252) , P. dielsiana Pilger (1928: 107–108) , P. orbignyana Steinheil ex Decaisne (1852: 704) (with 4 subspecies), P. pachyneura von Steudel (1849: 406) , P. subnuda Pilger (1912: 260) and P. truncata von Chamisso & von Schlechtendal (1826: 170–171) as distinct species. Therefore, Rahn kept P. pretoana as a subspecies of P. australis , as it doesn’t have a taproot. In his new definition ( Rahn 1974), P. australis was to have many secondary fibrous roots but not a taproot, and almost always a short and rather inconspicuous caudex, but seldom, although always in P. australis subsp. pretoana , a long and thickened (to 11 × 3 cm) rhizome.

Although Rahn (1964, 1974) described P. australis subsp. pretoana as having 1-seeded pyxidia, he admitted that he had probably not seen well-formed seeds. Indeed, in the material we observed, we found that plants of this species are normally 3-seeded, and 1-seeded pyxidia, although not rare, do not seem to contain a well-formed seed. It is important to note that the specimen illustrated in the Figure 36 in Rahn (1974) [L.B. Smith et al. 7712, HBR] is not P. pretoana ( Hassemer et al. 2015a) ; the identity of this specimen is still unknown, it might belong to an undescribed species, but more material is necessary to resolve this question. Contrary to Rahn (1974), we found that P. pretoana does not occur in Rio Grande do Sul and Santa Catarina states, as the specimens from there attributed to this species [B. Rambo 34589, S and B. Rambo 51492, HBR] were shown to be P. australis subsp. australis , except for L.B. Smith et al. 7712 [HBR] (see above). Our revision of the material of P. pretoana (actually most of these specimens, originating from Serra do Itatiaia, were previously identified as P. dielsiana ; see Hassemer et al. 2015a) confirms that these specimens constitute a distinct species, forming a morphologically, geographically, and ecologically well-defined group.

Figures

FIGURE 2. Plantago pretoana. A. Habit. B. Detail of scape. C. Detail of a trichome from scape. D. Bract, dorsal face. E. Anterior sepal, dorsal face. F. Posterior sepal, dorsal face. G. Flower. H. Fruit. I. Seed, dorsal side. J. Seed, ventral side. K. Seed, transversal section. From J.M. Silva & J. Cordeiro 7554 (MBM), illustrations by Marina Clasen Baumann.

FIGURE 3. Distribution of Plantago australis subsp. angustifolia (stars), P. napiformis (dots) and P. pretoana (triangles). Refer to the legend of the identification key for the abbreviations of the territories in the map.