Pseudotrimezia nana Lovo & Mello-Silva, 2015

Lovo, Juliana & Mello-Silva, Renato, 2015, Two new species of Pseudotrimezia (Iridaceae) endemic to Diamantina Plateau, Minas Gerais, Brazil, Phytotaxa 195 (2), pp. 145-153 : 146-149

Pseudotrimezia nana Lovo & Mello-Silva , sp. nov. ( Figs. 1A–D & 2A–E )

Species quam maxime affinis P. pumilae habitu caespitoso humilique, quae tamem bracteis rami floriferi 2 imbricatis et pedunculo papilloso differt.

Type:— BRAZIL. Minas Gerais, Gouveia: Contagem, fazenda Galheiros , de Júlio Caetano Rodrigues (vulgo Júlio Barbalho), ca. 3 km em estrada vicinal a leste da rodovia Gouveia-Curvelo ( BR 259 ), ao sul da fazenda Contagem, e 8, 8 km ao sul do Córrego do Tigre , Sopés da extremidade norte da Serra do Indaial , base de inselberg próximo ao Ribeirão da Contagem , elev. 1130 m, 18°36’01.9”S 43°52’55.5”W, 8 December 2012 (fl, fr), J. Lovo, S. F. Alcantara & L. H. M. Fonseca 418 (holotype, SPF!; isotypes, K!, NY!, RB!) .

Perennial herbs often caespitose, less frequent solitary, 3.5–10 cm total length, underground stem conical, 2.3–5.5 × 2.4–5 mm, storage absent, enclosed by light brown, fibrous, lustrous, spirally arranged persistent leaf sheaths forming an ovoid corm 1.5–2.4 × 0.4–0.7 cm. Living leaves 4 to 13 at anthesis, 1.5–6.5 × 0.1 cm, cylindrical, linear, filiform, light green, straight, slightly curved, apex attenuate. Flowering stem 3.5–5 × 0.1 cm, simple, erect, round in cross section, purplish to green, with two imbricated bracts present more or less in the middle; portion below the bracts 3–4 cm long, sparsely papillose, portion above bracts (inflorescence peduncle) 0.5–1 cm long, densely papillose. Bracts of the flowering stem lanceolate, outer ones 5–13 × 2–3 mm, inner ones 5–6 × 2 mm. Bracts of the inflorescence (rhipidial spathes) two, imbricate, lanceolate, outer ones 4–6 × 2–3 mm, inner ones 5 × 2–2.5 mm, apex acuminate, enclosing (2–)3 flowers. Pedicel 3.5–4 × 0.4 mm. Flowers erect, hypanthium 1.0–1.5 × 0.8 mm, perigone yellow, pale yellow towards the proximal region and with vinaceous pigmentation on the basis, spread out; tepals patent, plane, apex with non-glandular multicellular trichomes; outer tepals obovate, 6.1–7 × 3 mm, apex emarginated, inner tepals narrower, oblanceolate, 6.4–6.8 × 2.2–2.4 mm, apex acuminate; filaments flat, free, 2 × 1.8–2 yellow; anthers narrowly oblong, 1.8–2 × 0.5–0.7 mm, yellow, adpressed to the style; style yellow, entire up to ca. 2.5–3 mm long, then divided with three free branches, filiform, ca. 0.9 mm long, apex entire, fimbriate, with an apical pore-like, slightly lineate stigmatic zone. Capsule loculicidal, subglobular, 3-lobed, light brown to slightly gold in mature state, 1.4–2.4 × 1.5–3 mm.

Leaf anatomy:—Leaf unifacial, squared in cross section. Stomata randomly distributed. Epidermis uniseriate. Papillae absent. Strands of epidermal sclerified cells present in the outermost part of the leaf. Four vascular bundles, one in each corner of the leaf, the xylem poles oriented towards the centre and the phloem generally not entirely enclosed by fibres. Central parenchyma with large cells, merging with the mesophyll with rounded smaller cells ( Fig. 3A ).

Distribution and habitat:— Pseudotrimezia nana is endemic to Galheiros farm, in Gouveia municipality, Minas Gerais State, Brazil ( Fig. 4 ), where it grows on rocky and sandy wet soil, on the base of an “inselberg”, near to populations of P. synandra Ravenna (1965: 320) . Despite they both seem to be endemic to this small area of the Diamantina Plateau , and occupy the same niche, the two species were not found in co-occurrence.

Conservation status:—Only one population of this species has been found so far, outside a conservation unit and with a very small extent of occurrence. Besides, the population is located in the nearby of human occupancy, including a region of mineral extraction. Therefore, according to IUCN criteria (2014), P. nana should be classified as Critically Endangered (CR, B1ab(i, ii, iii)+2ab(i, ii, iii)).

Phenology:— Pseudotrimezia nana flowers in December, the anthesis beginning at 2 p. m. It has been found with dried, opened fruits, in January.

Etymology:—The specific epithet is a reference to the overall size of this species, which is among the smallest within the genus, second only to P. pumila .

Taxonomic relationships:— Pseudotrimezia nana is easily recognized by the very small, caespitose habit, with various slender leaves. The flowering stem densely covered with papillae ( Fig. 1C , 2D ), especially in the distal portion, is unique within the genus. Pseudotrimezia nana is similar to P. pumila Ravenna (2000: 8) and they share resembling habits. They both occur very closely in Diamantina Plateau. Pseudotrimezia pumila is only known from the type material and could not be found afterwards. They are the smallest species of Pseudotrimezia , being highly distinct from the other species of the genus ( Table 1). Despite all their similarities, P. nana is slender and more delicate, although taller, than P. pumila , and has two imbricated bracts in the median part of the flowering stem, which are absent in P. pumila . Furthermore, the presence of papillae in the peduncle of P. nana is also distinctive of these two species. The leaves of P. nana are longer and thinner than the leaves of P. pumila , they have four vascular bundles, and the epidermis in the region between them is flat, thus resulting in a square shape in transversal section ( Fig. 3A ), whereas in P. pumila there are six vascular bundles, and the epidermis between them is depressed, thus resulting in a rounded shape in transversal section ( Fig. 3D ). Finally, the central parenchyma in leaves of P. nana is solid, while it is fragmented and formed by aerenchyma in P. pumila . Although growing very close to Pseudotrimezia nana , P. synandra Ravenna (1965: 320) , is quite different from the previous one. This later is much larger and robust, lacks bracts on the flowering stem and, flowers a month latter, in January, and the anthesis takes place latter afternoon, at 5 p. m.

Additional specimen examined (paratypes):— BRAZIL. Minas Gerais: Gouveia: Contagem, fazenda Galheiros, de Júlio Caetano Rodrigues (vulgo Júlio Barbalho), ca. 3 km em estrada vicinal a leste da rodovia Gouveia-Curvelo (BR 259), ao sul da fazenda Contagem, e 8, 8 km ao sul do Córrego do Tigre. Sopés da extremidade norte da Serra do Indaial, base de inselberg próximo ao Ribeirão da Contagem, elev. 1135 m, 18°35’58.2”S 43°52’54.4”W, 24 January 2012 (fr), J. Lovo, S.F. Alcantara, R. Mello-Silva, F.P.B. Lima, K.D. Pinto, L.F. Nascimento & Y.K.S. Sanches 313 (NY!, SP!, SPF!).

Figures

FIGURE 1. Pseudotrimezia nana (from the holotype). A. Habit; B. Rhipidium with mature fruits; C. Flowering stem (peduncle) with papillae; D. Underground system (corm) in longitudinal section; Pseudotrimezia striata (from the holotype); E. Habit; F. Flower; G. Rhipidium with mature fruits; H. Underground system in longitudinal section.

FIGURE 2. Pseudotrimezia nana (from the holotype). A–B. Habit; C. Flower; D. Flowering stem (peduncle) in detail, with papillae; E. Longitudinal section of underground system (corm); Pseudotrimezia striata (from the holotype). F. Habit; G. Flower; H. Leaf in longitudinal section showing diaphragms or trabeculae (arrow); I. Underground system (corm) in longitudinal section.

FIGURE 3. A. Pseudotrimezia nana, cross section of middle region of leaf (Lovo 313); P. striata (Lovo 297); B. Cross section of the proximal region of the leaf, showing unfused margins and the flowering stem in the centre; C. Cross section of a distal portion of the leaf; D. P. pumila, cross section of middle region of leaf (Hatschbach 49677); E. P. planifolia, cross section of middle region of leaf (Lovo 147); F. P. synandra, cross section of middle region of leaf (Lovo 74).

FIGURE 4. Geographic distribution of Pseudotrimezia nana and P. striata in Diamantina Plateau, Minas Gerais State.