A new species of Sipapoantha ( Gentianaceae : Helieae ) from northern Brazil

A new species from Gentianaceae (tribe Helieae) is described from northern Brazil. Sipapoantha obtu­ sisepala sp. nov. is distinct from the previously single member of the genus, Sipapoantha ostrina, by having a woody and branched habit, sessile and ovate leaves with an acute apex, and a smaller calyx with circular lobes. Sipapoantha obtusisepala is based on somewhat incomplete material and tentatively placed in Sipapoantha based on the pres- ence of key generic characters such as coriaceous leaves with strongly revolute margins and blue corollas. It has only been recorded from one locality in the Brazilian-Guyana border area in the state of Roraima.


INTRODUCTION
The rare genus Sipapoantha Maguire & B.M.Boom is known from only a handful of herbarium specimens and until now has been considered a monotypic genus (Struwe et al. 1999).The type species, S. ostrina Maguire & B.M.Boom, is a perennial herb endemic to the Guayana Highlands region of Venezuela, and more specifically, it occurs only in the state of Amazonas on the tepui mountains (flat-topped mesas) of Cerro Sipapo, Cerro Cuao and Cerro Autana.
Sipapoantha obtusisepala, described here for the first time, is a woody shrub known from only a single herbarium specimen collected on a mountain in the Brazilian-Guyana border area in the Brazilian state of Roraima.It differs from S. ostrina in its woody and branched habit, sessile ovate leaves with an acute apex, and a smaller calyx with circular lobes, but the two taxa share coriaceous leaves with strongly revolute margins that are sulphur yellow in colour when dry and blue corollas.A new morphological description of Sipapoantha is provided due to its new circumscription, as well as a new generic key.
Sipapoantha is a member of the neotropical tribe Helieae (Gentianaceae; Struwe et al. 2002Struwe et al. , 2009)).The latest phylogeny, based on 127 morphological characters and DNA sequences (matK, trnL intron and ITS), placed Sipapoantha as part of a polytomy with the two major subclades, the Macrocarpaea clade and the Symbolanthus clade (note that this placement is tentative due to a lack of molecular data for Sipapoantha; Struwe et al. 2009).Sipapoantha obtusisepala has the typical Helieae characters of terminal compound cymes with a pair of scale-like bracts subtending each flower, calyx lobes rounded with a dorsal glandular area, medially dehiscing capsule with a woody pericarp, and numerous angular seeds (Struwe et al. 1999(Struwe et al. , 2002(Struwe et al. , 2009)).

MATERIALS AND METHODS
Morphological characters were collected from herbarium specimens from IAN, K, MO, NY, U and US.All measurements and sketches were taken from dried, pressed material.A ruler was used to measure peduncle length and leaf dimensions, while all other measurements were observed using an eyepiece scale of an Olympus dissecting scope at 10× or 50× magnification.The terminology used to describe structures follows Stearn (1999).The abbreviations for herbaria follow 'Index Herbariorum' (Holmgren & Holmgren 1998).Stamens included in corolla mouth; filaments flattened (when dry), of unequal length, 28 -39 mm long, inserted very close to base of corolla tube, widened and winged at the base; anthers lanceolate sagittate, 7-8 mm long, straight after anthesis, versatile, with a sterile apex; pollen in tetrads with pilate to verrucose exine (fide Nilsson 2002).Ovary sessile, with a glandular disk below ovary; style flattened in fruit (when dry, then also twisted), persistent or deciduous; stigma broadly bilamellate (corolla, stamen and pistil characters not known from S. obtusisepala).Capsule ellipsoid, 10-18 mm long, green when immature, brown at maturity, woody, dehiscing medially, horizontal to nodding.Seeds angular, roughly cubical or conical, 0.2-0.8mm diam, brown.Sipapo, Dept.Atures, summit of northern section, savanna type vegetation along a small stream, 1500 m, 5°N 67°30 ' W, 17 Feb. 1981, Steyermark et al. 124554 (MO, NY).Etymology.The name obtusisepala derives from the Latin 'obtusus' meaning rounded and 'sepalum' meaning sepal.This name was chosen to reflect the obtuse apices of the calyx lobes.
Distribution -Brazilian state of Roraima, in the Brazilian-Guyana border area.
Habitat & Ecology -Sipapoantha obtusisepala is known from only one specimen growing among rocks on the Sierra Baeta mountain.

DISCUSSION
The species described here has been tentatively placed within Sipapoantha based on shared macroscopic morphological characters.Table 1 provides a character comparison of S. ob tusisepala, S. ostrina and other Helieae taxa with which the newly described species share diagnostic characters.The coriaceous leaves of S. obtusisepala are similar to those of S. ostrina, Prepusa Mart., and Rogersonanthus Maguire & B.M.Boom.The revolute leaf margin is also a character found in Sipapoantha and Calolisianthus, as well as, in one species of Prepusa (P.montana Mart.) and Rogersonanthus (R. quelchii Maguire & B.M.Boom).Although there are similarities, it does not seem likely that the new species is part of Prepusa due to the 6-merous flowers and the chartaceous, showy and inflated calyx characteristics of that genus.Calolisianthus is another genus with vegetative similarities to S. obtusisepala, but with subcoriaceous leaves, this genus does not appear to be the best choice.In addition, Prepusa and Calolisianthus are endemics to the Brazilian Highlands, making the placement of the new species into these unlikely from a geographic standpoint.
Chelonanthus Gilg has many species found in the Guayana Highlands, but the vegetative morphology and habit fail to point Taxon (# of characters  Table 1 A comparison of five taxa with Sipapoantha obtusisepala using ten morphological characters.Characters in bold are those shared with the new Sipapoantha species.Numbers in parentheses below each taxon name represent the number of characters shared with S. obtusisepala.Note: Rogersonanthus in this circumscription does not include R. coccineus, which has been moved to Roraimaea (Struwe et al. 2008).
to this genus as the best choice.When comparing the generic characters, it is apparent that S. ostrina and Rogersonanthus share the most characters with the new species, S. obtusi sepala (Table 1).All three taxa have coriaceous leaves evenly dispersed along the stem, revolute leaf margins and 5-merous flowers with a coriaceous, green calyx.The characters that S. ostrina shares with the new species, and which exclude it from Rogersonanthus, are the sulphur yellow colour of the dried leaves and blue corollas.Rogersonanthus, on the other hand, shares with the new species a woody habit.Both genera occur in the Guayana Highlands region, making each a good candidate geographically.Considering there are a number of genera in Helieae that are composed of woody and herbaceous species (Macrocarpaea (Griseb.)Gilg, Neblinantha Maguire, Prepusa, Rogersonanthus and Symbolanthus G.Don), placement of the new species within Rogersonanthus based on that character seems inappropriate.Therefore, the most logical placement for the new species is in Sipapoantha, based on the colour and texture of its dried leaves and blue corollas.
In the circumscription presented here, Sipapoantha is a montane genus endemic to the Guayana Highlands, albeit strongly disjunct (Map 1).Sipapoantha ostrina is known from only a few herbarium specimens from tepuis in the western part of the mountain range, and S. obtusisepala is found on a mountain outlier in the southeast, c. 1000 km from S. ostrina.It is likely that additional collections in this understudied area of the Neotropics will find additional populations of Sipapoantha taxa.
Sipapoantha obtusisepala is unique in the genus in its woody, branching habit.It also differs in having sessile leaves that are smaller in size with an acute apex, as opposed to S. ostrina's petiolate leaves with an obtuse apex.The 6 -7 mm long calyx of S. obtusisepala is smaller than the 8 -10 mm long calyx of S. ostrina.Calyx lobe shape differs as well, with a circular shape found in S. obtusisepala and an ovate-oblong shape found in S. ostrina.
The collection site of the S. obtusisepala type specimen is not clearly stated on the herbarium label.The label reads "Roraima, Serra Baeta, perto de Suriname", which means "Serra Baeta, nearby Suriname".It is not clear from the label if the location is referring to Roraima, the state in Brazil, or Mt Roraima on the tri-border of Brazil, Guyana and Venezuela.In addition, neither the state nor the mountain is located near the Suriname border.
All efforts to locate Serra Baeta had been fruitless until a specimen of a different genus was found that was likely collected during the same expedition.This specimen A second map, 'The Guianas and Guyana' (International Travel Maps 2004) shows multiple peaks within the area as well as the area east of the New River in Guyana as under dispute and claimed by Suriname.This would explain Ribeira's description of "… perto de Suriname …" Map 1 illustrates all of the location evidence we currently have from these two collections.Searches through online databases of specimens at MO, NY and US have not revealed any other collections from Serra Baeta (Baieta).
The collection of A. cullmaniorum is also interesting because it reveals a highly disjunct population of this species.Aripuana was previously thought to be endemic to the lowland white sand areas of southeastern Amazonas in the border area of the states Rondônia, Mato Grosso and Pará (Struwe et al. 1997).
The new genus Roraimaea, also in the tribe Helieae, was recently described from white sand areas of Roraima (Struwe et al. 2008).Gentianaceae are not heavily collected in this state and we expect new and interesting populations, and possibly species, to be added to the scientific record in the future.
The generic placement of S. obtusisepala is tentative, but we are confident that our study has revealed a new species.When working with rare specimens it is often difficult to come across herbarium material suitable for DNA extraction and additional data is needed to have greater confidence in the generic placement presented here.It is apparent, however, that the new species is distinct.Considering the rarity of S. obtusisepala, we believe its documentation crucial.Making others aware of this unique taxon will aid in data collection and understanding.

Fig. 1
Fig. 1 Sipapoantha obtusisepala Lepis, Maas & Struwe.a. Flowering stem in the fruiting stage; b. leaves with prominent midvein and one pair of prominent, arcuate secondary veins; c. young capsule with persistent calyx, style and stigma and older capsule with apical portions of style and stigma missing; d. angular seeds with sunken sides and ridges (all Ribeiro 369, IAN).
of another Helieae gentian, Aripuana cullmaniorum Struwe, Maas & V.A.Albert, was collected from the same mountain, on the same day, by B.S. Pena (Pena 365, IAN).This second (and remarkable, see below) collection of A. cullmaniorum provided enough information to narrow down the location to several peaks on the border of the Brazilian states of Roraima and Pará with Guyana.The Aripuana label reads, "On Serra Baieta 200 km from Anauá, quadrat NA-21-Y-A, RADAM Project, Federal Territory of Roraima."We located the mentioned quadrant on the RADAM website (http://www.adimb.com.br/radam.htm)and were able to pinpoint the village Anauá on 'A Traveller's Reference Map of Amazon Basin', map # 421 (International Travel Maps 1998).

Map 1
Map illustrating the disjunct distribution of the genus Sipapoantha as well as the proposed collection site of the S. obtusisepala type.The smaller map inserted in the upper left corner of Brazil, Guyana and Venezuela, shows the type species, S. ostrina (symbol ■) found on the tepuis in the western part of the Guayana Highlands in Venezuela.The location of the newly described species, S. obtusisepala, is believed to have been collected in the grey area near the town of Anauá, on the border of Brazil and Guyana.The larger map shows the proposed collection area in greater detail (see discussion for details).The area in grey represents the RADAM Project quadrat NA-21-YA.The area outlined by ----represents a 200 km distance from the town of Anauá.The ▲ symbol represents mountain peaks.