Paepalanthus serpens, a new microendemic species of Eriocaulaceae from the Espinhaço Range, Minas Gerais, Brazil

Abstract We describe and illustrate Paepalanthus serpens, a microendemic species of Eriocaulaceae from the Espinhaço Range. The species is known from a single population growing in rocky areas of the Serra do Cipó, Minas Gerais. It is placed in Paepalanthus ser. Paepalanthus, and is easily distinguished from its congeneric species by its elongated, lignescent stem, thickened by the marcescent sheaths of the linear leaves, which are arranged in a rosette at the stem apex, scapes equalling the leaf height, and capitulae with straw-coloured involucral bracts. Comparisons with the morphologically similar species are provided, as well as comments on distribution, ecology, phenology and conservation status.


Introduction
Paepalanthus Mart. is the largest genus of Brazilian Angiosperms, comprising around 360 species in the country (Forzza et al. 2010). Th e genus is highly diversifi ed in the Espinhaço Range, in both of its subunits, in Bahia and Minas Gerais states. Elevated areas in Goiás state are a secondary center of diversity in Brazil Hensold 1991, Giulietti et al. 2012). As a large genus, have some authors subdivided Paepalanthus into many series, based mostly on rough external morphology (Koernicke 1863, Ruhland 1903). Paepalanthus ser. Paepalanthus (=Paepalanthus ser. Variabiles Ruhland) is the largest category, encompassing around 200 species (Ruhland 1903, Silveira 1908, 1928. Species placed in this series present trimerous fl owers and a particular architecture, usually consisting of a short, horizontal, and subterraneous stem, rarely lignose and elongated, with congest leaves at the apex, which are mostly arranged in rosettes (Ruhland 1903). Paepalanthus ser. Paepalanthus appears polyphyletic (Andrade et al. 2010, Giulietti et al. 2012), but further taxonomic and phylogenetic researches are necessary to enhance a stable classifi cation. Th erefore, assignments of species to it are possibly provisional. Recent fi eldwork and herbarium studies revealed that in spite of the large number of species in this series, there are still many others to be described (e.g. . Based on herbarium specimens and recent fi eld eff orts, we describe a remarkable new species of Paepalanthus, and place it within P. ser. Paepalanthus. Diagnosis. Paepalanthus serpens diff ers from the other species of the genus by its elongated, lignescent stem, thickened by the marcescent sheaths of the linear leaves, which are disposed in rosette at the stem apex, scapes equalling the leaf length and capitula with straw-coloured involucral bracts.
Conservation status. Th e species is considered critically endangered according to criteria B1a and B2a of the IUCN (2011). However, it occurs inside a conservation unit (RPPN Toucan Cipó) and is conserved ex situ at the Belo Horizonte Botanical Garden (Fundação Zoo-Botânica de Belo Horizonte, FZB-BH), factors that may attenuate its threatened status.
Etymology. Th e epithet serpens refers to the serpent-like habit of the perennial individuals, which have an unbranched, thick woody stem that slowly elongates and becomes creeping, with an erect apex.
Comments. Th e extremely reduced population and restricted occurrence range probably contributed to this species remaining undescribed. It occurs on high slopes with diffi cult access from the closest trails and roads.
Th e species architecture and trimerous fl owers place Paelanthus serpens within P. ser. Paepalanthus (Ruhland 1903), which is the largest of the genus, encompassing most of its morphological, taxonomic and phylogenetic complexity (Andrade et al. 2010, Giulietti et al. 2012. Usually species within this series are hard to identify (Andrino 2013), making the confi dent recognition of new species challenging. Paepalanthus serpens, however, is very diff erent from the other species of the series in several aspects. It can be easily distinguished by its robust habit, with an elongate, lignescent stem, thickened by marcescent leaf sheaths, bearing at the apex a rosette of linear and erect leaves, numerous scapes equalling the leaf height and capitula with straw-coloured involucre. Th is character set is unique within the genus. Other peculiar features are the scape spathes, which are quite short (up to 1 cm) and membranaceous, with lacerate margins, and short ferrugineous trichomes on the leaves and scapes. In addition, in some individuals, the trichomes on the bracts and fl owers become yellowish after drying, which is an unusual feature within the genus.
Th e species of Paepalanthus with similar overall morphology to P. serpens are P. caespititius Mart. ex Koern. and P. brunnescens Ruhland. Both have a similar size and linear leaves, but more delicate habit and short, non-lignescent stem. Th ese species are also not sympatric to P. serpens, as none of them are reported to the Serra do Cipó. Paepalanthus caespititius is morphologically the most similar species, with similar leaf width and short scapes, surpassing the leaves by no more than 5 cm. However, it shows dark involucral bracts and lanose stem with long ferrugineous hairs. Paepalanthus brunnescens resembles P. serpens by its straw-coloured capitulum involucre, but can be easily diff erentiated by its short, branched stem, scapes greatly surpassing the leaf height, larger leaves, and elliptic to lanceolate involucral bracts.