Pseudotrimezia striata 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 : 149-152

Pseudotrimezia striata Lovo & Mello-Silva , sp. nov. ( Figs. 1E–H & 2F–I )

Ab omnibus speciebus generis foliis striatis glaucisque etiam vaginis et basibus foliorum basim ramorum floriferorum amplectentibus optime distincta.

TYPE: — Brazil. Minas Gerais, Diamantina: Estrada para Conselheiro Mata , a 31, 9 km do entroncamento com a estrada Diamantina-Gouveia ( BR 367 ), elev. 1119 m, 18°18’36.1’’S 43°55’06.7’’W, 18 January 2012 (fl, fr), J. Lovo, S. F. Alcantara, R. Mello-Silva, F. P. B. Lima, K. D. Pinto, L. F. Nascimento & Y. K. S. Sanches 297 (holotype, SPF!; isotypes, K!, RB!) .

Evergreen perennial herbs 20–40 cm total length; mostly solitary, sometimes slightly caespitose; underground stem conical, 1.2–1.7 × 0.7–2.5 cm with reddish to light yellow storage, enclosed by persistent brown, fibrous, spirally arranged leaf sheaths forming a depressed-ovoid corm 4–9 × 1.5–4.5 cm. Living leaf one, present during anthesis, cylindrical, 23–40 × 0.25–0.5 cm, linear, glaucous, straight, apex attenuate, conspicuously parallel-striate; leaf sheath dorsiventral with unfused margins extending up to 7–16 cm long, folded, wrapping the proximal portion of the flowering stem, then margins fused and lamina unifacial. Flowering stem 3.4–12 × 0.15–0.2 cm, simple, erect, round in cross section, light green, partially enclosed by the leaf, free portion 1.5–3.5 cm. Bracts of the inflorescence (rhipidial spathes) two, imbricate, lanceolate, outer ones 25–42 × 6 mm, inner ones 28–38 × 7 mm, apex acuminate, enclosing 2–3 flowers. Pedicel 15–25 × 0.5 mm. Flowers erect, hypanthium clavate, 3.5–3.8 × 2.3 mm, perigone golden yellow, proximal region slightly spotted with vinaceous dots, spreading; tepals patent, plane, apex with non-glandular multicellular trichomes; outer tepals obovate, 12.5–17 × 5.3–7.2 mm, apex acute; inner tepals narrower, oblanceolate, 10–13.5 × 2.5–3.5 mm, apex acuminate; filaments flat, free, 1.8–2.5 × 0.4, light yellow; anthers narrowly oblong, 6.1–8 × 1.2 mm, dark yellow, addressed to the style; style light yellow, connate near the base, ca. 5.5 mm long, free style branches filiform, ca. 2.5 mm long, apex entire, fimbriate, with an apical pore-like, slightly lineate stigmatic zone. Capsule spheroid, loculicidal, 3-lobed, brown in maturity, 8–19 × 5–6 mm.

Leaf anatomy:—Blade round in cross section. Leaf sheathing bifacial, with unfused margins. Blade of the leaf unifacial. Papillae present on the surface of ridges. Depressions smooth, present between vascular bundles, with stomata distributed through those areas. One large vascular bundle opposite to each ridge, with phloem poles towards epidermis, entirely encircled by fibres. Smaller vascular bundles generally opposed to the larger ones, and a few alternating or randomly disposed and oriented. Mesophyll with rounded cells, slightly palisade-like between vascular bundles. Conspicuous longitudinal aerenchyma alternating with diaphragms (trabeculae) present in the centre of the leaf ( Figs. 2H , 3B, C ).

Distribution and habitat:— Pseudotrimezia striata is endemic to “Campo Rupestre” vegetation in Diamantina Plateau , Minas Gerais State, Brazil ( Fig. 4 ), where it grows on sandy soil, among open herbaceous vegetation.

Conservation status:— Pseudotrimezia striata has been found in three distinct areas along the Diamantina-Conselheiro Mata road, in the Diamantina Plateau. It is difficult to evaluate the actual extension of its populations, but it might be that its absence from the collections is due to insufficient sampling effort in the region ( Rapini et al. 2008). Nevertheless, all the known populations are limited to a small extent of occurrence and not located inside any conservation unit. Moreover, the region is subject to habitat fragmentation by the development and extension of settlements and agriculture. Thus, according to IUCN Red List criteria ( IUCN 2014), the species should be considered Endangered (EN, B1ab(i, ii)+2ab(i, ii)).

Phenology:— Pseudotrimezia striata flowers in January, the anthesis beginning at ca. 5 p. m. It has been found with fruits in March.

Etymology:—The epithet “ striata ” is a reference to the conspicuous striation of the leaves, given by its several longitudinal ridges.

Taxonomic relationships:— Pseudotrimezia striata can be easily recognized by peculiar characteristics. The wide, glaucous, sharply striated leaves, with papillae restricted to the ridges, and the unfused foliar margins extending from the sheath and enclosing the flowering stem, which lacks bracts, constitute a combination of features not found elsewhere within the genus and the tribe Trimezieae . Pseudotrimezia striata resembles P. planifolia Ravenna (1988: 51) in the habit, in the presence of just one leaf with similar wide shape during the flowering period, and in the underground system, with reddish to yellow storage. They differ in leaf cross-section form, rounded in P. striata versus narrowly elliptic in P. planifolia , in the extended dorsiventral sheath, present only in P. striata , in the deep leaf furrows, present only in P. planifolia , in the papillae, conspicuous and restricted to the ridges in P. striata and inconspicuous and restricted to the furrows in P. planifolia , and in the leaf fibres, limited to the vascular bundles in P. striata , while forming girders in P. planifolia . Pseudotrimezia striata also resembles P. synandra Ravenna (1965: 320) . Both share the aphyllous flowering stem, unusual in the genus, but enclosed by the leaf in P. striata . The ovoid corm of P. synandra is quite distinct, accumulating just a few amount of light yellow storage, whereas the corms of P. striata are conical, more robust and show a reddish storage. Furthermore, P. synandra has no papillae, furrows or depressions in the leaves. Main characters distinguishing P. striata from its putative closer two relatives species are in table 2. One population of P. striata was observed growing in sympatry with P. sublateralis Ravenna (1988: 22) . These two are highly distinct, mainly by the leaf, which encloses the flowering stem in P. striata and is absent during flowering period in P. sublateralis . This latter species also flowers earlier than P. striata , in August and September.

Additional specimen examined (paratypes):— BRAZIL. Minas Gerais: Diamantina. Estrada para Conselheiro Mata, a 31, 9 km do entroncamento com a estrada Diamantina-Gouveia ( BR 367 ), elev. 1119 m, 18º18’36.1”S 43º55’06.7”W, 21 November 2012 (fr), J. Lovo & S. F. Alcantara 362 ( MO!, SPF!) ; Galheiros, 5, 1 km da estrada Diamantina-Conselheiro Mata ( MG 220 ), entrada a 13, 9 km da rodovia Diamantina-Datas ( BR 367 ), elev. 1307 m, 18°15’21.7”S 43°48’29.5”W, 14 January 2014 (fl, fr) J. Lovo, M. M. T. Cota & R. Mello-Silva 462 ( NY!, SP!, SPF!) ; estrada Diamantina-Conselheiro Mata ( MG 220 ), 21 km da estrada Diamantina-Datas ( BR 367 ), grande “inselberg” quartzítico com campo limpo na base, próximo à estrada, elev. 1221 m, 18°17’41.9”S 43°50’49.2”W, 15 January 2014 (fl, fr) J. Lovo, M. M. T. Cota & R. Mello-Silva 466 ( NY!, 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.