Actinocephalus delicatus Sano, 2011

Echternacht, Livia, Trovó, Marcelo & Sano, Paulo Takeo, 2011, Two new species of Actinocephalus (Eriocaulaceae) from Minas Gerais, Brazil, Phytotaxa 27, pp. 26-36 : 27-31

Actinocephalus delicatus Sano , sp. nov. ( Figs. 1 , 2 )

Ab Actinocephalo brachypo habitu rhizomatoso, foliis glabris, scapis pilosis, bracteis paracladiorum intus glabris, bracteis florum apicibus et sepalorum apicibus obtusis, bracteis involucralibus hialine usque ad brunnea et floribus pistillatis pedicellatis differt.

Type:— BRAZIL. Minas Gerais: Felício dos Santos, APA Felício dos Santos, Cachoeira do Sumidouro , 1350 m, 18 o 13’S, 43 o 15’W. 19 June 2006, P. L . Viana, F. S. F . Leite, L. E . Lopes & M . Ferreira 2512 (holotype SPF, isotype BHCB) .

Perennial herbs, 10–18 cm tall, with a rhizome producing basal rosettes, and paraclades axillary to the rosette leaves with an umbel of inflorescences at its apex. Rhizome 1–6 cm long. Leaves rosulate, flat, patent, linear, 3.0–6.5 × 0.1–0.2 cm, glabrous, apex acute, margin glabrous. Paraclades 1–5 per rosette, unramified, 6.5–16.5 × 0.3 cm, hirsute; paracladial bracts distributed along the paraclade and subtending the umbel of capitules, erect, linear, 1.0–2.5 × 0.1–0.2 cm, adaxial surface glabrous, abaxial surface glabrescent, apex acute, margins glabrescent, base semiamplexicaul. Spathes 0.3–0.5 cm long, glabrous, apex acute. Scapes 18–35 per paraclade, 1.5–2.0 cm long, tomentose with simple trichomes; capitula 2–4 mm in diameter, hemispheric; involucral bracts hyaline to light-brown, obovate, ca. 2 mm long, glabrous, apex obtuse, ciliate toward the apex; receptacle hemispheric, pubescent. Flowers 3-merous, ca. 14 per capitula: 10 staminates, 4 pistilates; floral bracts castaneous to golden-brown, oblong, concave, ca. 2 mm long, glabrous, apex obtuse, ciliate toward the apex. Staminate flowers ca. 2 mm; pedicel ca. 0.5 mm long, with long trichomes; sepals colored like floral bracts, fused at the base, obovate, concave, ca. 1 mm long, glabrous, apex obtuse, ciliate toward the apex; corolla tubular, membranaceous, hyaline, ca. 1.5 mm long, 3-lobed, glabrous; stamens ca. 2 mm long; pistillodes 3, papillose. Pistillate flowers ca. 2 mm; pedicel ca. 0.5 mm long, glabrous; sepals colored like floral bracts, obovate, concave, ca. 2 mm long, glabrous, apex obtuse, ciliate toward the apex; petals hyaline, oblong, ca. 1 mm long, glabrous, apex acute, ciliate toward the apex; gynoecium ca. 2 mm long, stigmatic branches completely fused, twice as long as the nectariferous branches; staminodes 3, scale-like. Fruit a loculicidal capsule.

Distribution and ecology:— Actinocephalus delicatus is terrestrial or rupicolous and occurs in open areas, growing over rocky to sandy soils of the northeastern Espinhaço Range in Minas Gerais, Brazil. The species is known to occur in two distinct localities ( Fig. 3 ): (1) in the Cachoeira do Sumidouro, in the Felício dos Santos municipality, a place predicted to be included in the Rio Preto State Park, where only a few individuals were found; and (2) in the Serra Negra State Park, in the Itamarandiba municipality, where a population of hundreds of individuals occurs throughout the Serra Negra. The individuals in the Cachoeira do Sumidouro were found in the riverbed, suggesting an aquatic habitat. These specimens were collected in June, in the dry season, so that it is unlikely that terrestrial individuals were flooded. However, we went to the area in the same season and, despite our intense search in the river edges and all around, we were unsuccessful to recover the species. As aquatic Actinocephalus are unknown, we suggest that the species is terrestrial, but some seeds germinated accidentally in the dry riverbed, where they were able to survive for a short while, without forming a perennial population. In addition, all the individuals in the Serra Negra are terrestrial or rupiculous, occurring in dry conditions, on sandy, free-draining soil.

IUCN Red List category:— Actinocephalus delicatus is considered endangered (E) according to criteria B2a (IUCN 2008).

Etymology:—The epithet refers to the delicate habit of the species, with its membranaceous leaves, and small and narrow paraclades.

Notes:— Actinocephalus delicatus matches morphological architectural pattern I (sensu Oriani et al. 2008) due to its paraclades arising directly from a short aerial stem. Of all species exhibiting this pattern, A. delicatus shares morphological similarities with A. brachypus (Bong.) Sano (2004: 101) and A. herzogii (Moldenke) Sano (2004: 103) . From the other Actinocephalus species it can be easily differentiated by its linear leaves, hirsute paraclades, hyaline to light-brown involucral bracts, and pedicelate pistillate flowers.

Actinocephalus brachypus is the species morphologically most similar to A. delicatus . It shows approximately the same size of leaves, paraclades, and paracladial bracts, spathes and scapes, as well as a similar capitulum diameter. These common features give them a similar general habit, however they are easily distinguished, particularly by indumentum characters. Actinocephalus delicatus is a rhizomatous herb (vs. rhizome absent), with glabrous leaves (vs. hispid and ciliate), hirsute paraclades (vs. glabrous), and glabrous adaxial surface of the paracladial bracts (vs. hispid). It exhibits floral bracts and sepals of both staminate and pistillate flowers with obtuse apex (vs. acute). These species are also distinguished by the hyaline to light-brown involucral bracts (vs. dark-brown) and pedicelate pistillate flower (vs. sessile) in A. delicatus . Actinocephalus brachypus occurs in campos rupestres on the Diamantina Plateau (Minas Gerais), on roadsides between Diamantina and Gouveia ( Sano 1999). Until now, both species were considered allopatric.

Actinocephalus herzogii is divided into two varieties, distinguished mainly by overall size ( Sano 1999). Individuals of Actinocephalus herzogii var. humilis (Sano) Sano (2004: 103) are distinctly smaller, and morphologically similar to A. delicatus . Both are rhizomatous herbs with linear leaves, hairy paraclades and scapes. They have approximately the same size of paraclades and spathes and pedicelate pistillate flowers, a very unusual characteristic in the genus. Actinocephalus delicatus is distinguished by its longer leaves (3.0– 6.5 cm vs. 2.0– 2.5 cm) with glabrous margins (vs. ciliate), linear erect paracladial bracts (vs. lanceolate patent), spathes with acute apices (vs. truncate), and glabrous sepals of the pistillate flowers (vs. hairy in abaxial surface base). Actinocephalus herzogii var. humilis occurs in campos rupestres on Chapada Diamantina (BA) , in the vicinity of Piatã ( Sano 1999), thus, these species occur allopatrically.

Paratypes:— BRAZIL. Minas Gerais: Itamarandiba. Parque Estadual da Serra Negra , 18 o 00’ 20.2’’S, 42 o 43’ 28.9’’W, 13 September 2006, R. C . Mota , A. P . Fontana & K. A . Brahin 3089 ( BHCB); Parque Estadual da Serra Negra , 18 o 00’ 31.7’’S, 42 o 43’ 46.7’’W, 1477 m, April 2010, L . Echternacht , T. V . Bastos , T. E . Almeida & A. M . de O. Santos 2140 ( BHCB, P, SPF) .

Figures

FIGURE 1. Actinocephalus delicatus. A. Habit. B. Young capitulum. C. Involucral bract abaxially. D. Floral bract of the staminate flower abaxially. E. Staminate flower immature. F. Staminate flower immature with sepals removed and corolla opened. G. Pistillate flower. H. Gynoecium. (Drawn from the holotype)

FIGURE 2. Photographs of Actinocephalus delicatus. A. Habit. B. Inflorescence and capitula. C. Habitat in the Serra Negra State Park. D. Population and habit, individuals with immature inflorescences (Photos: Claudio Nicoletti—A, B and D—and Livia Echternacht—C).

FIGURE 3. Distribution map of Actinocephalus delicatus (black squares) and Actinocephalus giuliettiae (black stars).