DOI: 10.5061/dryad.h8p4p
title: Data from: Floral convergence in Oncidiinae (Cymbidieae; Orchidaceae): an expanded concept of Gomesa and a new genus Nohawilliamsia

description: BACKGROUND: Floral morphology, particularly the angle of lip attachment to
 the column, has historically been the fundamental character used in
 establishing generic limits in subtribe Oncidiinae (Orchidaceae), but it
 has also been long recognized that reliance on this character alone has
 produced a highly artificial set of genera. In essence, lip/column
 relationships reflect syndromes associated with pollinator preferences;
 most genera of Oncidiinae as previously defined have consisted of a single
 floral type. Here, the degree to which this has influenced generic
 delimitation in Brazilian members of the largest genus of Oncidiinae,
 Oncidium, which previous molecular (DNA) studies have demonstrated to be
 polyphyletic, is evaluated. METHODS: Phylogenetic analyses of the
 following multiple DNA regions were used: the plastid psbA-trnH intergenic
 spacer, matK exon and two regions of ycf1 exon and nuclear ribosomal DNA,
 comprised of the two internal transcribed spacers, ITS1 and ITS2, and the
 5·8S gene. Results from all regions analysed separately indicated highly
 similar relationships, so a combined matrix was analysed. KEY RESULTS:
 Nearly all species groups of Brazilian Oncidium are only distantly related
 to the type species of the genus, O. altissimum, from the Caribbean. There
 are two exceptions to this geographical rule: O. baueri is related to the
 type group and O. orthostates, an isolated species that lacks the defining
 tabula infrastigmata of Oncidium, is not exclusively related to any
 previously described genus in the subtribe. Several well-supported
 subclades can be observed in these results, but they do not correspond
 well to sections of Oncidium as previously circumscribed or to segregate
 genera as defined by several recent authors. In spite of their floral
 differences, these groups of Oncidium, formerly treated as O. sections
 Barbata, Concoloria pro parte, Crispa, Ranifera, Rhinocerotes, Rostrata
 (only O. venustum), Synsepala, Verrucituberculata pro parte and Waluewa,
 form a well-supported clade with Gomesa (including Rodrigueziella and
 Rodrigueziopsis) embedded in it. Two often recognized segregate genera,
 Baptistonia and Ornithophora, and the recently described Carriella are
 also embedded within the Brazilian clade. The level of variation within
 major subclades of the Gomesa clade is low and similar to that observed
 within other genera of Oncidiinae. CONCLUSIONS: Convergence on a
 stereotypical syndrome of floral traits associated with pollination by
 oil-collecting bees has resulted in these characters not being reliable
 for producing monophyletic taxa, and the genus Oncidium, defined by these
 characters, is grossly polyphyletic. Vegetative and a few
 floral/inflorescence characters link these taxa with a mainly Brazilian
 distribution, and they were all transferred to Gomesa on this basis rather
 than separated from Gomesa based on their floral differences, which we
 hypothesize to be simple shifts in pollination strategies. Other authors
 have described a large number of new genera for these former members of
 Oncidium, but most of these are not supported by the results presented
 here (i.e. they are not monophyletic). A new genus, Nohawilliamsia, is
 described for O. orthostates because it does not fit in any currently
 recognized genus and is only distantly related to any other member of
 Oncidiinae.
description: Gomesa
 3'ycf1Nexus matrix of
 3'ycf1 sequences of various Oncidiinae
 (Orchidaceae)Gomesa
 5'ycf1Nexus matrix of
 5'ycf1 sequences of various Oncidiinae
 (Orchidaceae).Gomesa
 ITSNexus matrix of nrITS
 sequences of various Oncidiinae (Orchidaceae).Gomesa
 matKNexus file of matK
 sequences of various Oncidiinae (Orchidaceae).Gomesa
 psbA-trnHNexus matrix of
 psbA-trnH sequences of various Oncidiinae
 (Orchidaceae).