Paepalanthus conjunctus Trovó, 2014

Trovó, Marcelo & Sano, Paulo Takeo, 2014, Paepalanthus conjunctus, a new species of Paepalanthus sect. Diphyomene (Eriocaulaceae) from Central Brazil, Phytotaxa 178 (1), pp. 53-56 : 53-55

Paepalanthus conjunctus Trovó , sp. nov. (Fig. 1)

Differs from the remaining species of Paepalanthus sect. Diphyomene by its cespitose habit forming clumps of a few individuals, linear leaves, short reproductive axis, hairy scapes, and shortened corolla tubes.

Type: — BRAZIL. Distrito Federal: Recanto das Emas, Núcleo Rural Monjolo , 11 August 2009, A. E . Ramos, F. P. R . Jesus, G. C . Reis, G . Cota, M . Oliveira 1878 (holotype HEPH!) .

Figure 1. Paepalanthus conjunctus Trovó.A. Habit. B. Involucral bract abaxial surface. C. Floral bract abaxial surface. D. Pistillate flower (juvenile). E. Staminate flower with sepals removed. F. Staminate flower (Ramos 1878, HEPH).

Herbs forming clumps of a few individuals, 31−43 cm tall; rhizome present, aerial stem ca. 3.0 cm long. Leaves persistent, linear, flat, erect, 9.0−21.5 × 0.1−0.3 cm, apex acute, pubescent to glabrescent, younger ones with margin ciliate. Reproductive axis erect, 1.5−3.5 cm long, 0.3 cm diameter, glabrous; all axis bracts with similar shape, amplexicaul, chartaceous, linear, erect to sub-erect, 5−6.5 × 0.2−0.3 cm, apex acute, glabrescent, younger ones with margin ciliate. Spathes 3.5−5.5 cm long, glabrous, apex acute. Scapes ca. 5−20 per plant, arranged in an obconic umbel, 20−40 cm long, pubescent. Capitula 6−9 mm diameter, hemispheric to spherical when old, white; involucral bracts in 3 to 4 series, brown, linear to rarely lanceolate, flat, ca. 3 mm long, glabrous or abaxially pubescent, margin ciliate toward the apex, apex acute; receptacle semi-spherical, pubescent. Flowers dimerous, ca. 75 per capitulum, ca. 70 staminate and 5 pistillate; floral bracts linear, brown to golden, flat, ca. 3 mm long, abaxially pubescent to glabrous, margin ciliate toward the apex, apex acute. Staminate flowers ca. 3 mm long; pedicel ca. 0.5 mm long, with long trichomes; sepals navicular, brown to golden, ca. 3 mm long, abaxially pubescent to glabrous, margin ciliate toward the apex, apex mucronate; fleshy anthophore elongated; corolla fused, bilobate, shortened, hyaline, membranaceous, ca. 0.5 mm long; stamens ca. 1.5 mm long; pistillodes 2, papillose. Pistillate flower (juvenile) ca. 2 mm long, sessile; sepals navicular to dolabriform, brown to golden, ca. 2 mm long, abaxially pubescent to glabrous, margin ciliate toward the apex, apex mucronate; petals obovate, hyaline, ca. 0.4 mm long, abaxially pubescent, margin ciliate toward the apex, apex rounded; gynoecium ca. 1 mm long, stigmatic branches bifid, as long as the nectariferous branches, staminodes completely reduced. Fruits and seeds not seen.

Etymology: —The epithet “ conjunctus ” refers to the tufted habit of the species, forming small clumps of individuals.

Distribution, Habitat, and Conservation: —A single flowering population is known from the vicinity of Brasilia, Distrito Federal. The species grows in open humid fields intermixed with grasses. Paepalanthus conjunctus is classified as endangered according to criteria B1, B2a i, and B2a of the IUCN (2011).

Additional specimens examined: — BRAZIL. Distrito Federal: Recanto das Emas, Núcleo Monjolo , 10 May 2010, Ramos A . E . et al. 1959 ( HEPH); 10 May 2010, Ramos A . E . et al. 1963 ( HEPH); 10 May 2010, Ramos A . E . et al. 1969 (HEPH).

Comments: — Paepalanthus conjunctus has a combination of rare features (described in the diagnosis) that clearly distinguishes it from the other species in Paepalanthus sect. Diphyomene . It has linear leaves erectly disposed along the short stem. This feature is shared with Paepalanthus linearis Trovó (2013a: 327) , a species possessing a much longer reproductive axis (31−40 cm vs. 1.5−3.5 cm), restricted to the north of the Espinhaço Range in Minas Gerais. Hairy scapes are only found in Paepalanthus sericiscapus Trovó (2013a: 329) , Paepalanthus arcuatus Trovó (2013a: 325) , and Paepalanthus decussus Koern (1863: 318) . These species are all easily segregated from P. conjunctus by their lanceolate leaves. Additionally, they are restricted to Minas Gerais. The growing habit forming clumps attached by the rhizome is also found in Paepalanthus polycladus Silveira (1928: 189) . Paepalanthus polycladus can be differentiated from P. conjunctus by its longer reproductive axis (30−80 cm vs. 1.5−3.5 cm) and its short lanceolate leaves.

Herbarium specimens of Paepalanthus conjunctus may be misidentified as Paepalanthus elongatus (Bongard 1831:630) Koern. (1863: 312) due to their linear leaves and linear involucral bracts with acute apex. Paepalanthus elongatus belongs, however, to Paepalanthus ser. Dimeri Ruhland (1903: 166) , a group of species without reproductive axes. Although some old capitula of Paepalanthus conjunctus were examined, only a few juvenile pistillate flowers were found. The low frequency of pistillate flowers could be a sampling artifact or may be indicative of low allocation of resources for sexual reproduction, explaining also the tufted habit of the individuals. Further investigations are required for an assertive answer to this question.