Plantago napiformis ( Rahn 1964: 56–57 ) 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 : 230

Plantago napiformis ( Rahn 1964: 56–57) Hassemer , comb. et stat. nov.

≡ P. paralias subsp. napiformis Rahn (1964: 56–57) ; ≡ P. tomentosa subsp. napiformis ( Rahn 1964: 56–57) Rahn (1974: 139–141) . Type:— ARGENTINA. CORRIENTES: Empedrado: Estancia Las Tres Marías, dry grassland on the top of the bank of Río Paraná, soil black earth, 22 November 1962, T.M. Pedersen 6650 (holotype C!).

Rosette herbs, 5–58 cm tall, perennial, often darkening slightly on drying. Taproot usually thickened and napiform above; caudex 0.3–2.0 × 0.4–1.9 cm, with sparsely-distributed brownish orange hairs. Leaves 4.1–21.0 × 1.0– 3.7 cm, 4- to 7-veined, chartaceous; petiole rather distinct; lamina elliptic to obovate, with trichomes 0.7–2.8 mm long, type G, sparsely-distributed and variously-directed, but much more densely pilose along the veins of the abaxial surface; margin weakly to strongly toothed, ciliate; apex acute to obtuse. Inflorescence 6–58 cm long. Scape 3–38 cm long, cylindrical, generally with longitudinal grooves; trichomes 1.5–3.0 mm long, type G, densely-distributed, patent. Spike 3–20 cm long, usually subequal to the length of the scape, cylindrical, multi-flowered, with flowers densely packed above, less densely crowded below. Bracts narrowly triangular, rarely triangular, 1.7–3.0 × 0.7–1.0 mm, dorsal face pilose, margin ciliate. Anterior sepals narrowly elliptic to almost oblanceolate, 2.1–2.6 × 0.7–1.0 mm; keel pilose; margin glabrescent; apex mucronulate. Posterior sepals oval to elliptic, 2.2–2.9 × 0.9–1.6 mm; keel pilose; margin glabrescent; apex acute or mucronulate. Corolla actinomorphic, glabrous; lobes ovate, 2.0– 3.1 mm long, shorter than the sepals, patent or erect; apex acuminate. Stamens 4. Ovary with 3 ovules; pyxidium 2.4–3.3 × 1.3–1.6 mm, 3- seeded. Seeds narrowly ellipsoid to ovoid, slightly convex ventrally, convex dorsally, 1.4–2.2 × 0.7–1.2 mm; surface reticulate, light to dark brown.

Illustrations: — Figure 1 ; also Figure 78 in Rahn (1974).

Phenology: —Flowering August–January, fruiting September–February.

Habitat and distribution: —Occurs in rather dry grasslands in southern Paraguay, northeastern Argentina (Chaco, Corrientes, Formosa, Misiones and Santa Fe) and southern Brazil (Rio Grande do Sul) ( Figure 3 ).

Conservation status: —Near Threatened (NT). This species has a rather restricted distribution, and it is not very frequent. Furthermore, it does not appear to thrive in disturbed habitats, as the known collections of this species are from natural grasslands. Although probably not currently threatened with extinction, the destruction of the natural grasslands in Corrientes, Argentina and in southern Paraguay would certainly endanger the survival of this species. It may already be regionally threatened in Brazil, as it is known from only two localities there (Giruá and Santa Maria), and has not been collected there since 1975. We recommend further studies of the populations of this species to allow for better understanding of its distribution, conservation status and intraspecific variation.

Discussion: — Plantago napiformis , previously classified as a subspecies of P. tomentosa de Lamarck (1791: 340) , is however morphologically more similar to P. catharinea Decaisne (1852: 726) than to P. tomentosa ; P. napiformis can be distinguished from these two species by its roots, caudex, leaves and seeds ( Table 2), and by ecology. The distribution of P. napiformis and P. catharinea do not overlap, as the latter is restricted to coastal vegetation (“restingas”) in southern Brazil.

As previously treated ( Rahn 1964, 1974, 1995), the circumscription of P. tomentosa included plants with both rugose and reticulate seeds, and with both slender and wide trichomes. This situation made it impossible to correctly identify specimens of P. napiformis using identification keys such as those in Rahn (1966) and Hefler et al. (2011). The rugose seeds and the unusually slender type G trichomes are defining of P. tomentosa , as no other species in section Virginica have either of these characteristics; in contrast, P. napiformis has reticulate seeds and stiff and wide type G trichomes, as do many other representatives of section Virginica . Based on its morphology, and also on environmental differences, we consider that P. napiformis warrants species rank.

Figures

FIGURE 1. Plantago napiformis. 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 K. Hagelund 5690 (ICN), 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.