Identity of the Brazilian species Dioscorea pumilio Griseb . and its synonyms

1. Instituto de Botánica Darwinion, Labardén 200, Casilla de Correo 22, San Isidro, Buenos Aires, Argentina 2. Instituto de Botânica, Núcleo de Pesquisa Curadoria do Herbário SP, Av. Miguel Stéfano 3687, 04301-902, São Paulo, SP, Brasil 3. Autor para correspondência: mkirizawa@uol.com.br ABSTRACT (Identity of the Brazilian species Dioscorea pumilio Griseb. and its synonyms). Dioscorea pumilio, a dwarf species, was originally described by Grisebach in 1875 based on staminate material only, which was obtained from a few fl owered and fl oral bud collection made by A. Glaziou. The diagnosis and the drawings with the authorʼs handwriting in the exsiccates deposited at the Göttingen Herbarium (GOET), and the isotypes at the Herbaria of Paris (P), Copenhagen (C) and Berlin (B), are enough to elucidate the identity of the species. Two synonyms of Dioscorea pumilio, D. beyrichii and D. sphaeroidea, are proposed here. All three names were based upon type materials collected at the same site of the “Parque Nacional da Serra dos Órgãos”, Brazil. A brief comment about the systematic implications is also included.


Introduction
The detailed examination of types and the revision of valid names of Dioscoreaceae as part of the taxonomic research of Dioscoreaceae of the Brazil Flora Group -BFG (2015) allowed the identifi cation of some forgotten or misunderstood names.In the present study, we indicated the correct name of some taxa described from the same site located near or in the proximities of the summit of the "Parque Nacional da Serra dos Órgãos", Rio de Janeiro State, Brazil.Furthermore, we cited for the fi rst time additional material studied from "Parque Estadual do Desengano", Rio de Janeiro, Brazil.

Material and methods
The taxonomic analyses were based upon type materials of Dioscorea pumilio Griseb., D. beyrichii R. Knuth, and D. spharoidea R. Couto & M.A. Braga obtained from exsiccates with authorʼs handwriting deposited at the Goettingen Herbarium (GOET) and from the isotypes deposited at the Herbaria of Paris (P), Copenhaguen (C) and Berlin (B), besides studies on these species published by Grisebach (1842), Knuth (1917Knuth ( , 1924) ) and Couto et al. (2014).All these species of Dioscorea were collected in the same area of "Pedra do Sino", which currently belongs to "Parque Nacional da Serra dos Órgãos", a component of orographic system of Serra do Mar.

Results and Discussion
The analysis of protologues enabled the accurate identification of Dioscorea pumilio Griseb.Observations: although the type material of D. pumilio at Berlin only mentioned Rio de Janeiro, the isotype conserved at Paris referred ¨Sommet des Orgãos", 12-X-1869, male.On the other hand, in Beyrich 3 the collection site of D. beyrichii was annotated as "Partem Corco": Corco might be an apocope of the Portuguese word "corcova" that means hump, properly describing the top of the mountain at "Pedra do Sino", which means bell´s stone.
Finally, D. sphaeroidea was recognized as a dwarf plant with creeping branches, small discoid tubers, staminate flowers with three stamens and a flattened pistillode.
The main differences between the type materials of D. pumilio Griseb.and D. beyrichii R. Knuth is that the former plant stands strictly erect while the second is a dwarf plant with twinning stems.The condition was explained by Burkill (1960), for dwarf dioscoreas growing in grasslands, no taller -than the associated grasses; but if it chances to be where the soil is good enough to support a bush, it profits by the increased moisture and shade to be just tall enough to twine.On the other hand, Schubert (1966) in her publication mentioned the expected difficulties while studying species of Dioscorea.She commented the results based upon mixed collections for which specimens of both sexes were not available, and therefore the species were described from only specimens of one sex.At the time D. pumilio was described, the original material had not fruits.The first pistillate collection assigned to the species was Nadruz et al. 1782 (RB), published by Couto et al. (2014), which was considered by these authors as a new species, D. spharoidea.Due to the presence of a rounded fruit and a spherical wingless seed, these authors concluded that the infrageneric position of this species is uncertain and consequently, the assignment to a subgenus or a section was not possible.
The presence of wingless spherical seeds in a Dioscorea species is not a novelty.Burkill (1960) pointed out that dwarf plants of Dioscorea might lose the seed wings, giving examples and explanations.
The infrageneric subdivision of Dioscorea into subgenera is based on the characteristics of the seeds.The sectional delimitation was first provided by Grisebach (1842) and D. pumilio was included originally in the section Allactostemon Griseb.and it was subsequently transferred to Hemidematostemon Griseb., a section pertaining to the subgenus Dioscorea, whose members have rounded seeds.However, Burkill (1960) and Knuth (1924) considered that D. pumilio may belong to another section of the same subgenus, Polyneuron Uline.Uline (1897) assigned six species to this section, all of them from Mexico.The characterization of this section is adequate because two dwarf plants are included there, and because in the description of D. multinervis Benth.Uline annotated "semina globose".This datum comes from the original diagnosis of its synonym D. nana Schlechtendal (1844) non Poepp.that mentioned "fructus subglobosi, trianguli, ad angulos verrucose, 2 semina globose gerentibus".
Meantime, due to its wingless seeds, D. pumilio cannot be assigned to a proper section and thus should be considered as section incertae sedis in Dioscorea L. subg.Dioscorea.This study highlights the need for revaluation of the infrageneric classification of Dioscorea, particularly in the case of sectional assignment of D. pumilio.