Paepalanthus sect. Diphyomene Ruhland, 1903

Trovó, Marcelo & Sano, Paulo Takeo, 2010, Taxonomic survey of Paepalanthus section Diphyomene (Eriocaulaceae), Phytotaxa 14, pp. 49-55 : 50-51

Paepalanthus sect. Diphyomene Ruhland in Engler, Pflanzenr. IV. 30 (Heft 13): 184 (1903).

Lectotype (here designated): Paepalanthus urbanianus Ruhland.

= Paepalanthus (Diphyomene) [unranked] Vestiti Ruhland in Engler, Pflanzenr. IV. 30 (Heft 13): 184 (1903). Lectotype (here designated): Paepalanthus acanthophyllus Ruhland , syn. nov.

= Paepalanthus (Diphyomene) [unranked] Foliosi Ruhland in Engler, Pflanzenr. IV. 30 (Heft 13): 184 (1903). Lectotype (here designated): Paepalanthus urbanianus Ruhland , syn. nov.

Herbs, 0.4– 3 m. Rhizome present, aerial stem 0.5–5.0 cm long. Rosette leaves persistent or deciduous when flowering, linear to lanceolate, flat, patent to contort, 1.5–35.0 × 0.1–3.0 cm, glabrous or hairy on both surfaces, margin entire, ciliate or glabrous, apex rounded to acuminate. Reproductive axis elongate, erect, 17– 295 cm long, 0.2–2.0 cm diam., glabrous; reproductive axis bracts linear to lanceolate, chartaceous, recurved to erect 1.5–15.0 × 0.3–2.0 cm, glabrous or hairy on both surfaces, apex round to acuminate, margin entire, ciliate or glabrous, base semi-amplexicaul to amplexicaul. Spathes 2.0– 8.5 cm long, glabrous, apex opening oblique, acute. Scapes 10–850, arranged in spherical to obconical umbels, 18–32 cm long, glabrous. Capitula 0.5–1.5 cm diam., discoid to semi-spherical; involucral bracts in 3 to 5 series, light-brown to dark-brown, obovate to ovate, concave, ca. 0.3 cm long., glabrous, margin ciliate or glabrous, apex obtuse to acute; receptacle semi-spherical, hairy. Flowers dimerous, 50 to 350 per capitulum; floral bracts linear, light-brown to dark-brown, concave, hairy or glabrous on the abaxial surface, ciliate or glabrous toward the apex, apex acute; staminate flowers ca. 0.3 cm long; pedicel ca. 0.1 cm long, with long hairs; sepals navicular, lightbrown to golden, hairy or glabrous on the abaxial surface, ciliate toward the apex, apex rounded to acute; anthophore carnose, elongated; corolla tubular, hyaline, membranaceous; stamens free; anthers dithecoustetrasporangiate, pistillodes 2, papillose; pistillate flowers disposed in concentric bands, ca. 0.3 cm, sessile; sepals dolabriform, light-brown to golden, hairy or glabrous on abaxial surface, ciliate toward the apex, apex obtuse; petals obovate, membranaceous to carnose, hyaline, hairy or glabrous on abaxial surface, ciliate or glabrous toward the apex, apex rounded to acute; gynoecium with bifid stigmatic branches and simple nectariferous branches; staminodes absent. Fruit a loculicidal capsule. Seeds with reticulate surface, red to brown.

Bongard (1831) described the first six Brazilian species of Eriocaulon L. as bearing dimerous flowers, three of them under the Staminibus duobus [unranked] taxon. Koernicke (1863) described Paepalanthus subgen. Dimeranthus Koernicke (1863: 312) to accommodate these species. Koernicke (1863) also described five new species, reduced to the status of synonym under those described earlier by Kunth (1841) and Steudel (1855), and constructed the first identification key for the species of this group. In this key, Koernicke (1863) distributed all into three groups: plants with short stems, plants with robust and elongated stems, and plants with gracile and elongated stems. The species belonging to Paepalanthus subgen. Dimeranthus were placed by Ruhland (1903) into three categories of his Paepalanthus subgen. Paepalocephalus Ruhland (1903: 122) (which should be correctly named Paepalanthus subgen. Paepalanthus , as it includes the type of Paepalanthus ): Paepalanthus sect. Conodiscus Ruhland (1903: 181) , Paepalanthus sect. Eriocaulopsis [unranked] Dimeri Ruhland (1903: 166), and P. sect. Diphyomene , the latter being subdivided into two categories: Paepalanthus [unranked] Vestiti Ruhland (1903: 184), with equal-sized leaves along the stem, and Paepalanthus [unranked] Foliosi Ruhland (1903: 184), with leaves of different sizes on both the stem and the basal rosette. Besides the supra-specific categories, Ruhland (1903) also described three new species and three new varieties.

Later, most taxonomic papers dealing with P. section Diphyomene were descriptions of new taxa. Herzog (1924) described Paepalanthus chiquitensis Herzog , from Bolivia, besides extending the distribution of the group. Silveira (1908, 1928) described four species and three varieties based on his own collections from Minas Gerais, Brazil. Moldenke (1952, 1964, 1971, 1974, 1978, 1983, 1987) described two species, seven varieties and two forms, the majority occurring in Brazilian savannas. Schultes (1954) described Paepalanthus moldenkeanus R.E.Schultes collected in Colombian savannas. Sano (2004) proposed a new name for the homonym Paepalanthus speciosus (Bong.) Koern. Finally, Trovó & Sano (2010) designated a lectotype for Paepalanthus neocaldensis Moldenke , and considered this name as synonymous of Paepalanthus flaccidus (Bong.) Kunth.

Trovó et al. (2010) when detailing the morphology and anatomy of inflorescences in P. sect. Diphyomene , concluded that there are two inflorescence types in this group, implying a further division. Species of the socalled group A correspond to those described by Koernicke (1863) as having robust, elongated stems, whereas those of group B correspond to the species having gracile, elongated stems ( Koernicke 1863). Trovó et al. (2010) also pointed out that group A species may be monocarpic and have leaves arranged in a basal rosette during the vegetative period, whereas group B species are always perennial and never present leaves in rosette form. Thus, with the morphological and life history evidence now available, the distinction proposed by Ruhland (1903) is of limited taxonomic value, only reflecting characters observed in herbarium reproductive collections.

Paepalanthus section Diphyomene comprises 10 species distributed throughout savannas and rocky outcrops in tropical South America. The center of species diversity is located in the savannas of the Brazilian state of Goiás. Most species are narrowly distributed and the limit of geographical distribution is given only by the distribution of Paepalanthus chiquitensis and Paepalanthus erectifolius Silveira.

In Paepalanthus section Diphyomene , inflorescences are spherical to obconical umbellate, arranged in a tribotryum with a terminal dibotryum, terminal basic unit and pherophylls (Trovó et al. 2010). The inflorescence structure in this group seems to be unique within Eriocaulaceae and represents a possible synapomorphy for this group. The following features are also important to distinguish this section from other groups in the Paepalanthus : dimerous flowers, pistillate flowers with dolabriform sepals, bifid stigmatic branches and absent staminodes, and staminate flower with an elongated anthophore. The necessary typifications and taxonomic changes are presented below.