Paepalanthus echinoides Trovó, 2015

Trovó, Marcelo, Silva, Arthur De Lima & Coan, Alessandra Ike, 2015, Paepalanthus echinoides (Eriocaulaceae), a new species from central Brazil with notes on leaf and scape anatomy, Phytotaxa 231 (1), pp. 81-88 : 82-86

Paepalanthus echinoides Trovó , sp. nov. Figs. 1 , 2

Paepalanthus echinoides differs from P. sphaerocephalus and P. exiguus mainly by its smaller leaves arranged in a rosette, the capillaceous and more numerous scapes, the smaller capitula, and the adpressed, dark brown spathes.

Type:— BRAZIL. Goiás: Alto Paraíso de Goiás, encontrada na beira da estrada para Fazenda Água Fria , no entroncamento com a rodovia GO-118, -14.070870, -47.507052, 12 March 2015, M. L. O. Trovó & A. L. Silva 647 (holotype, RB!; isotypes B!, NY!, SPF!) .

Herbs, usually solitary or forming small clumps, 6.0−11.0 cm tall; rhizome present, inconspicuous, aerial stem short ca. 0.5 cm long. Leaves persistent or rarely lacking in old individuals, chartaceous, linear, 1-veined, recurved, tufted to rosulate, 4.0−10 × 0.5−1 mm, apex acute, glabrous to sometimes sparsely pilose, margins glabrous to sometimes sparsely pilose. Spathes adpressed, equaling the leaves length, 5.0− 9.5 mm long, dark brown, glabrous, apex acute to sometimes truncate. Scapes ca. 35−160, arranged in a terminal cohort, 4.0−9.0 cm long, with most glabrous to rarely with sparse, adpressed trichomes. Capitula 1.2−2.0 mm diam., spherical, white; involucral bracts in 1 series, dark brown, obovate to obdeltoid, flat, ca. 1.5 mm long, glabrous, margin glabrescent, acuminate to mucronate; receptacle hemispherical to sub-cylindrical. Flowers dimerous, ca. 70 per capitulum, ca. 40 staminate and 30 pistillate; floral bracts resembling the involucral ones, just wider, hyaline, obdeltoid, ca. 2.0 mm long, glabrous, margin glabrescent, apex acuminate to mucronate. Staminate flowers ca. 1.0 mm long; pedicel ca. 0.3 mm long; sepals fused at the base, navicular, hyaline, ca. 0.8 mm long, glabrous, margin ciliate toward the apex to glabrescent, apex obtuse; anthophore fleshy, elongated; corolla fused in a tube, hyaline, membranaceous, ca. 0.8 mm long; stamens ca. 0.8 mm long; pistillodes 2, papillose. Pistillate flower ca. 1.0 mm long, sessile to shortly pedicellate; sepals not fused at the base, obcordate, hyaline, ca. 1 mm long, glabrous, margin ciliate toward the apex to glabrescent, apex emarginate; petals elliptic, hyaline, ca. 1mm (sometimes inconspicuous), margin glabrous, apex obtuse; gynoecium ca. 0.75 mm long, stigmatic branches bifid at the apex, 4 × longer than the nectariferous branches. Fruits a loculicidal capsule. Seeds elliptic, brown to reddish.

Etymology: —The epithet “ echinoides ” refers to the habit of the species and scapes arrangement, resembling a sea urchin.

Distribution, Habitat, and Conservation: — Paepalanthus echinoides has a very restrict distribution, known exclusively from the vicinities of the Chapada dos Veadeiros National Park in Alto Paraíso de Goiás ( Fig. 3 ). It occurs on dark, sandy soils, with abundant moisture and organic components. From the field observations and the map provided, the species has an area of occurrence (AOO) = 12 km ², occurring in locations under ecosystem degradation caused by roads and agriculture within and outside the boundaries of Chapada dos Veadeiros National Park. Considering the potential threats and the species restricted distribution, it is categorized as EN (endangered) - A3cd; B2ab (i,ii,iii,iv,v) ( Negrão 2015).

Additional specimens examined: — BRAZIL. Goiás: Alto Paraíso de Goiás, 24 April 1956, Dawson 14616 ( LL) ; 11 February 1966, Irwin et al. 12614 ( NY) ; 19 March 1969, Irwin et al. 24647 ( MO, NY) ; 20 February 1975, Hatschbach 36337 ( NY) ; 25 May 1975, Hatschbach 36867 ( LL) ; 09 May 1987, Menezes 1219 ( SPF) ; 25 July 1987, Romaniuc-Neto & Sajo 312a ( SPF) ; 08 May 2000, Munhoz et al. 1271 ( SPF) ; 10 March 2001, Munhoz et al. 2603 ( SPF) ; 27 March 2001, Munhoz et al. 2664 ( RB, SPF) .

Comments:— Paepalanthus echinoides is placed within P. sect. Conodiscus due to its dimerous flowers, small linear leaves, spherical capitula, and hemispherical to sub-cylindrical receptacle. In many herbaria, the specimens belonging to this new species have been erroneously identified as P. eriocauloides , which will be a synonym of P. sphaerocephalus (P.T. Sano, unpublished data). Paepalanthus echinoides may be distinguished within P. sect. Conodiscus by its smaller leaves arranged in a rosette, the capillaceous and more numerous scapes, the smaller capitula, and the adpressed, dark brown spathes.

Paepalanthus echinoides shares the very delicate habit, the capillaceous scapes and the relatively small capitula with Paepalanthus exiguus . The former can be easily distinguished from P. exiguus by the short aerial stem restricted to the rosette, the chartaceous leaves, the dark brown spathes, the numerous scapes per individual, and the dark brown involucral bracts ( Table 1). Furthermore, the two species are allopatric, with P. exiguus being restricted to the states of Minas Gerais and Bahia, distributed mainly in the Espinhaço Range ( Ruhland 1903).

The morphologically most similar species to Paepalanthus echinoides is P. sphaerocephalus , which is widely distributed in Brazil and sympatric with the new species in Goiás. Both are solitary and rosulate herbs, sometimes forming small clumps, growing in humid sandy soils. However, Paepalanthus echinoides is a more gracile plant, with many more scapes per individual. The new species can be also distinct by its most glabrous scape, spathes equaling the leaf length, capitula of ca. 2 mm diam., and staminate flowers pedicellate ( Table 1).

Anatomical Notes:— Leaves of P. echinoides have a single-layered epidermis (e) with very thin cuticle and sparsely distributed trichomes (tr) with small basal cells ( Fig. 4A–B ). In cross section, epidermal cells are rounded, thick-walled, and are smaller on the abaxial surface ( Fig. 4A ). In frontal view, they are narrow and longitudinally elongated ( Fig. 4B ). Paracytic stomata (st) are located on both surfaces and slightly above the other epidermal cells ( Fig. 4A–B ). The mesophyll comprises two regions of compact chlorenchyma (*) ( Fig. 4A, C ). Three vascular bundles are also present ( Fig. 4A ), being collateral and surrounded by a double sheath of slightly thick-walled cells; cells of the outer sheath (os) are larger than those of the inner one (is) ( Fig. 4A, C ). Bundle sheath extensions (se) display rounded, slightly thick-walled cells that reach both surfaces in the central bundle ( Fig. 4A ), but only the abaxial surface in the two lateral bundles ( Fig. 4A, C ).

Scapes of P. echinoides are formed by epidermis, cortex and a central cylinder ( Fig. 4D ). The epidermis is composed of a single layer of small, isodiametric, thick-walled cells with a reduced lumen. Stomata (st) are found slightly above the other epidermal cells and are restricted to the regions of chlorenchyma. Tector trichomes (tr) also occur. The cortex has three regions of compact chlorenchyma (*), forming slightly protruding ribs, alternating with three regions of sclerenchyma (sc) ( Fig. 4D ). The endodermis is discontinuous (en), forming a cap of thin-walled cells on the outer bundles of the central cylinder ( Fig. 4D ). The pericycle (pe) is stellate, composed of thick-walled cells, completely surrounding the outer vascular bundles and partially covering the inner ones. Pith in the central cylinder is reduced ( Fig. 4D ).

Anatomical data of representatives of Paepalanthus sect. Conodiscus are absent, so we compare the results of P. echinoides with the information available for other possibly closely related taxa of Paepalanthus with dimerous flowers, as P. sect. Diphyomene Ruhland (1903: 184) and P. subg. Thelxinoe Ruhland (1903: 199). Leaves of P. echinoides are anatomically similar to those of P. scleranthus Ruhland (1903: 199) (P. subg. Thelxinoe), due to the presence of trichomes on the epidermis, absence of hypodermis, narrow mesophyll, and a reduced number of vascular bundles ( Castro & Menezes 1995, Scatena et al. 2005). Scapes of P. echinoides show great similarity to the tricostate scapes of P. flaccidus ( Bongard 1831: 636) Kunth (1841: 511) (P. sect. Diphyomene) ( Trovó et al. 2010, Alves et al. 2013). Paepalanthus subg. Thelxinoe is characterized by the absence of scapes, thus the anatomical comparison of this organ was not possible. The presence of leaves with stomata on both surfaces and scapes with protruding ribs formed by both chlorenchyma and sclerenchyma are important anatomical characteristics to distinguish P. echinoides from the other dimerous taxa of Paepalanthus , contributing to the delimitation of P. sect. Conodiscus.

Figures

FIGURE 1. Paepalanthus echinoides. A. Habit. B. Capitulum detail. C. Receptacle detail. D. Involucral bract, abaxial surface. E. Floral bract, abaxial surface. F. Pistillate flower. G. Gynoecium. H. Staminate flower. I. Staminate flower with sepals removed and corolla opened. (M.L.O. Trovó & A.L. Silva 647 – RB).

FIGURE 2. Habitat and habit of Paepalanthus echinoides. A. Overview of the occurrence area in Alto Paraíso de Goiás (GO). B. Habit detail. C, D. Population detail. (Scale bars: B= 2cm; C= 4cm; D= 3cm).

FIGURE 3. Distribution map of Paepalanthus echinoides provided by CNCFlora following the standards described in Martinelli & Moraes (2013).

FIGURE 4. Anatomical sections of leaves and scapes of Paepalanthus echinoides (M.L.O. Trovó & A.L. Silva 647 – RB). A. Cross section of basal leaf. B. Paradermal view of epidermis of the abaxial surface. C. Leaf margin detail. D. Cross section of scape. (Scale bars:A= 100 μm; B= 50 μm; C–D= 25 μm).