Rapateaceae in the state of Pará , Brazil

Rapateaceae comprises approximately 19 genera and 131 species distributed in the Neotropics, with the exception of Maschalocephalus, which is endemic to West Africa. In Brazil, there are nine genera and 38 species. Th e present paper is based on a taxonomic study of the species of Rapateaceae that occur in the state of Pará. Botanical specimens from seven herbaria were analyzed and the occurrence of fi ve genera and eight species was confi rmed for the state. An identifi cation key to the genera and species, descriptions, illustrations and selected specimens are provided.


Introduction
Rapateaceae comprises approximately 19 genera and 131 species distributed in the Neotropics, with exception to the monotypic genus Maschalocephalus that is endemic to West Africa (Givnish et al. 2000).In Brazil, there are nine genera and 38 recorded species, which are distributed in every region except the South Region of the country (BFG 2015).
Th e fi rst publication about Rapateaceae was made by Aublet (1775), which introduced Rapatea paludosa Aubl.However, this species was not treated as a member of Rapateaceae until 54 years later when Dumortier (1829) characterized the family as having fl owers surrounded by large bivalvate spathes.Seubert (1847) published the fi rst taxonomic treatment of Rapateaceae, which comprises detailed descriptions of the family, three genera and six species, as well as an identifi cation key and illustrations.Following this, Körnicke (1873) published the fi rst large study about Rapateaceae that described nine new species.Maguire (1958;1962;1965;1979) refi ned the taxonomy of the family, and these studies remain the most important about the group.In addition, Givnish et al. (2000;2004) published the first phylogeny of the family, based on molecular data and morphological characters, which confi rmed the suprageneric taxa proposed by Maguire (1958;1962;1965;1979).
Although the richness of Rapateaceae is well-documented for Brazil, there are few taxonomic studies about the family for the country (Maguire 1958;Forzza & Costa 2005;Rodrigues & Flores 2010;Romanini & Wanderley 2012;Monteiro 2016), and for some states, such as Pará (Poeppig & Endlicher 1838;Maguire 1958), the publications about this group are old.For this reason, taxonomic studies about Rapateaceae in Pará are needed to identify specimens in Amazonian herbaria and to improve what is known about the fl oras of Amazonia and Brazil.
Th us, the present work aims to carry out a taxonomic treatment of Rapateaceae species in the state of Pará, deposited in the main amazonian and extra-amazonian herbaria, and thus providing data to contribute to the knowledge expansion about this family in the Amazon.
All Rapateaceae specimens (from Pará) at the herbaria MG, IAN, INPA, RB, MO, NY and P were studied; images of specimens at MO, NY and P were studied online, and species determinations were made after consulting the literature (Maguire 1958;1962;1965;1979;Berry 2004;Forzza & Costa 2005) and websites that have protologues and images of types Tropicos (2015), WCSP (2015) and Ithaka (2015).Some characters mentioned in protologues were not observed in the examined exsiccatae.These characters are included below the main description of the taxon as a "complimentary description."The terminology used to define the species is based on Maguire (1958;1962;1965;1979) and Berry (2004).
The identification keys, detailed descriptions, illustrations of important aspects and information about the habitat of each species are based on the material deposited at the consulted herbaria.The descriptions of genera are based on the same material and the literature (Maguire 1958;1962;1965;1979;Berry 2004;Forzza & Costa 2005).Accepted synonyms are found in Maguire (1958;1962;1965;1979).Geographic distribution, phytogeographic domain and phenology data were obtained from specimens and the literature.

Results and discussion
Approximately 190 specimens of the family were analyzed and five genera and eight species were confirmed for Pará, including Cephalostemon, Duckea, Saxofridericia and Spathanthus, with one species each, and Rapatea with four species.Rapateaceae Dumort., Anal. Fam. Pl.: 60 (1829).
Identification key to the Rapateaceae genera in the State of Pará   Schomburgk (1845) described C. gracilis based on the grass-like, linear leaf blades and inflorescence spikelets with bracteoles that have acuminate basal and long-aristate apical, confirmed these characteristics in all materials analyzed.Cephalostemon gracilis is very similar to C. affinis.The characters used to distinguish them (form of the base and apex of the bracteoles) were highly variable in the exsiccatae examined, including the types, and it was not possible to separate them.However, before synonymizing C. affinis, a more detailed taxonomic analysis of both taxa needs to be made that includes additional fertile material.
The main character that distinguishes Rapatea elongata from the other species in the genus is the elongate inflorescence, which was easily observed in the specimens studied.
In Brazil, R. elongata occurs in the states of Amazonas, Pará and Roraima, in campinarana, várzea fields, igapó forests and várzea forests, where it grows on the swampy margins of rivers and waterways.This species also occurs in Colombia, where is grows on the margins of rivers.Rapatea elongata flowers from February to July.
Rapatea paludosa is common throughout Pará and is well represented in Brazilian herbaria.The morphology of the specimens of R. paludosa analyzed was highly variable, mainly in relation to the size of the leaf blades (50.0-102.0cm long).In addition, the spathes usually envelop all of the spikelets but in some specimens from Mosqueiro Island (in the district of Belém) the spikelets pass beyond the spathes (laterally).
In general, the description in this paper is in accordance with the description proposed by Aublet (1775).However, Aublet described the scapes of R. paludosa as glabrous, and in the samples analyzed in the present study the scapes were sparsely pubescent.
This species is widely distributed in the Neotropics.In Brazil, R. paludosa occurs in the states of Acre, Amapá, Amazonas, Bahia, Mato Grosso, Pará, Rondônia and Tocantins, in campinarana, terra firme forest, várzea forest and rain forest, where it grows on the margins of rivers and waterways, and inundated areas.This species also occurs in Panama, Colombia, Venezuela, Suriname, French Guiana and Peru, where it grows in inundated areas.Rapatea paludosa flowers from January to October.
Complementary description: Flowers with whitish corolla, lobes obovate; anthers lanceolate; ovaries rounded; styles trigonous, apically swollen; stigmas apically papillose (Seubert 1847; Körnicke 1873).Data about the filaments was not found in the literature.Characters that can be used to identify Rapatea pycnocephala are glomerulate inflorescences and bracteoles with brown spots.R. pycnocephala can be distinguished from other species of the genus by its non-persistent spathes, which are lost at in the maturity.In addition, this species also has very characteristic leaf blades compared to the other species; R. pycnocephala has narrower leaf blades that are rarely more than 2.7 cm wide.
This species is endemic to Brazil and occurs in the states of Bahia, Goiás, Maranhão, Mato Grosso, Mato Grosso do Sul, Pará, Piauí, Rondônia and Tocantins, as well as the Distrito Federal, where it is found in cerrado, at the headwaters of rivers and in inundated areas.Rapatea pycnocephala flowers from August to December.
Rapatea ulei resembles R. paludosa by the capituliform inflorescence and the bivalvate, persistent spathes, but differs by its leaf blades with deeply cordate, asymmetrical leaf bases, rugose surfaces, prominent lateral veins on one side and spikelets with homogeneous bracteoles.Rapatea paludosa has leaf blades with attenuate, symmetrical bases, inconspicuously rugose surfaces, prominent lateral veins and spikelets with heterogeneous bracteoles.
In Brazil, this species occurs in the states of Amapá, Amazonas, Mato Grosso and Pará, where it grows in streams near shady areas and in swamp forest along waterways.
Rapatea ulei flowers from January to August.
Spathanthus unilateralis is characterized by univalvate spathes and young leaves with dark visible spots (mostly on inferior parts).The latter characteristic is not mentioned in any description related to S. unilateralis, but was observed on specimens during the present study.
In Brazil, this species only occurs in the states of Amapá, Amazonas and Pará, in campinarana, várzea fields, igapó forest and terra firme forest, where it grows in wetlands and affluents of waterways, rocky soils in humid areas, and around waterfalls.The species also occurs in French Guiana, Venezuela and Suriname, in swamp forests.Spathanthus unilaterais flowers from June to October.