Phylogenetics, ancestral state reconstruction, and a new infrafamilial classification of the pantropical Ochnaceae (Medusagynaceae, Ochnaceae s.str., Quiinaceae) based on five DNA regions.

Ochnaceae s.str. (Malpighiales) are a pantropical family of about 500 species and 27 genera of almost exclusively woody plants. Infrafamilial classification and relationships have been controversial partially due to the lack of a robust phylogenetic framework. Including all genera except Indosinia and Perissocarpa and DNA sequence data for five DNA regions (ITS, matK, ndhF, rbcL, trnL-F), we provide for the first time a nearly complete molecular phylogenetic analysis of Ochnaceae s.l. resolving most of the phylogenetic backbone of the family. Based on this, we present a new classification of Ochnaceae s.l., with Medusagynoideae and Quiinoideae included as subfamilies and the former subfamilies Ochnoideae and Sauvagesioideae recognized at the rank of tribe. Our data support a monophyletic Ochneae, but Sauvagesieae in the traditional circumscription is paraphyletic because Testulea emerges as sister to the rest of Ochnoideae, and the next clade shows Luxemburgia+Philacra as sister group to the remaining Ochnoideae. To avoid paraphyly, we classify Luxemburgieae and Testuleeae as new tribes. The African genus Lophira, which has switched between subfamilies (here tribes) in past classifications, emerges as sister to all other Ochneae. Thus, endosperm-free seeds and ovules with partly to completely united integuments (resulting in an apparently single integument) are characters that unite all members of that tribe. The relationships within its largest clade, Ochnineae (former Ochneae), are poorly resolved, but former Ochninae (Brackenridgea, Ochna) are polyphyletic. Within Sauvagesieae, the genus Sauvagesia in its broad circumscription is polyphyletic as Sauvagesia serrata is sister to a clade of Adenarake, Sauvagesia spp., and three other genera. Within Quiinoideae, in contrast to former phylogenetic hypotheses, Lacunaria and Touroulia form a clade that is sister to Quiina. Bayesian ancestral state reconstructions showed that zygomorphic flowers with adaptations to buzz-pollination (poricidal anthers), a syncarpous gynoecium (a near-apocarpous gynoecium evolved independently in Quiinoideae and Ochninae), numerous ovules, septicidal capsules, and winged seeds with endosperm are the ancestral condition in Ochnoideae. Although in some lineages poricidal anthers were lost secondarily, the evolution of poricidal superstructures secured the maintenance of buzz-pollination in some of these genera, indicating a strong selective pressure on keeping that specialized pollination system.

Floral convergence in Oncidiinae (Cymbidieae; Orchidaceae): an expanded concept of Gomesa and a new genus Nohawilliamsia.

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.

Molecular phylogeny of the neotropical genus Christensonella (Orchidaceae, Maxillariinae): species delimitation and insights into chromosome evolution.

BACKGROUND AND AIMS: Species' boundaries applied within Christensonella have varied due to the continuous pattern of variation and mosaic distribution of diagnostic characters. The main goals of this study were to revise the species' delimitation and propose a more stable classification for this genus. In order to achieve these aims phylogenetic relationships were inferred using DNA sequence data and cytological diversity within Christensonella was examined based on chromosome counts and heterochromatin patterns. The results presented describe sets of diagnostic morphological characters that can be used for species' identification. METHODS: Phylogenetic studies were based on sequence data of nuclear and plastid regions, analysed using maximum parsimony and maximum likelihood criteria. Cytogenetic observations of mitotic cells were conducted using CMA and DAPI fluorochromes. KEY RESULTS: Six of 21 currently accepted species were recovered. The results also support recognition of the 'C. pumila' clade as a single species. Molecular phylogenetic relationships within the 'C. acicularis-C. madida' and 'C. ferdinandiana-C. neowiedii' species' complexes were not resolved and require further study. Deeper relationships were incongruent between plastid and nuclear trees, but with no strong bootstrap support for either, except for the position of C. vernicosa. Cytogenetic data indicated chromosome numbers of 2n = 36, 38 and 76, and with substantial variation in the presence and location of CMA/DAPI heterochromatin bands. CONCLUSIONS: The recognition of ten species of Christensonella is proposed according to the molecular and cytogenetic patterns observed. In addition, diagnostic morphological characters are presented for each recognized species. Banding patterns and chromosome counts suggest the occurrence of centric fusion/fission events, especially for C. ferdinandiana. The results suggest that 2n = 36 karyotypes evolved from 2n = 38 through descendent dysploidy. Patterns of heterochromatin distribution and other karyotypic data proved to be a valuable source of information to understand evolutionary patterns within Maxillariinae orchids.

Byrsonic acid--the clue to floral mimicry involving oil-producing flowers and oil-collecting bees.

Tetrapedia diversipes and other Apidae (Anthophoridae) may be deceived by floral similarities between Malpighiaceae and Orchidaceae of the Oncidiinae subtribe. The latter do not usually exudate floral oils. Thus, visitors may pollinate the flowers in a deceit/food/pollination syndrome. We studied the chemical compositions of Byrsonima intermedia (Malpighiaceae) floral oil and T. diversipes (Anthophoridae) cell provisions. From B. intermedia floral oil, we isolated a novel fatty acid (3R, 7R)-3,7-diacetoxy-docosanoic acid, here named byrsonic acid, and from T diversipes cell provisions we isolated two novel fatty acid derivatives 3,7-dihydroxy-eicosanoic acid and 3,7-dihydroxy-docosanoic acid, here named tetrapedic acids A and B, respectively. The three fatty acid derivatives have common features: possess long chains (20 or 22 carbon atoms) with no double bond and either hydroxy or acetoxy groups at carbons 3 and 7. This characteristic was also encountered in the fatty acid moiety of oncidinol (2S, 3'R, 7'R)-l-acetyl-2-[3', 7'-diacetoxyeicosanyl)-glycerol, a major floral oil constituent of several Oncidiinae species (Orchidaceae). Thus, both tetrapedic A (C20) and B (C22) could be the biotransformation products of oncidinol and byrsonic acid by T. diversipes hydrolases. These are the chemical clues for bee visitation and oil collecting from both plant species. The results indicate that the deceit/pollination syndrome should not be applied to all Oncidiinae flowers.

Pollination by sexual mimicry in Mormolyca ringens: a floral chemistry that remarkably matches the pheromones of virgin queens of Scaptotrigona sp.

The chemical composition of some volatile (2-heptanol) and nonvolatile constituents (a homologous 9-alkene/alkane series) of Mormolyca ringens flowers and Scaptotrigona sp. queen waxes (homologous 9-alkene/alkane series) and cephalic extracts (homologous series of 2-alkanols, including 2-heptanol) involved with the pseudocopulation or sexual mimicry in Orchidaceae pollination is compared. The similarity in chemical composition of flowers and insects is assigned to the chemically induced copulatory activity in Scaptotrigona males.

The chemistry of pollination in selected Brazilian Maxillariinae orchids: floral rewards and fragrance.

We report the chemical composition of the floral rewards and the fragrance of 10 Maxillariinae (Orchidaceae) species. The species that offer rewards (labellar secretions) are usually scentless, the rewards being collected by bees. Chemical analyses revealed that the major chemical class of compounds present in the labellar secretions are triterpenoids. The rewardless Maxillariinae flowers were usually scented, and chemical analyses of their volatiles revealed that they were composed of mono and sesquiterpenoids.

Steroids and triterpenes from Eleocharis acutangula and E. sellowiana (Cyperaceae).

From the hexane extract of the underground parts of Eleocharis acutangula (Roxb.) Schult., lup-20(29)-ene-3beta,16beta-diol and a mixture of campesterol, stigmasterol and sitosterol were isolated. The hexane extracts of aerial and underground parts of E. sellowiana Kunth furnished two new substances, namely neohop-13(18)-en-3alpha-ol and stigmast-22-en-3beta,6beta,9alpha-triol, together with a mixture of steroids, betulinic acid, stigmast-4-en-6beta-ol-3-one and fern-9(11)-en-3alpha-ol. The molecular structures were determined by spectral analysis (1D- and 2D-NMR experiments and MS) and comparison with literature data.

Sexual mimicry in Mormolyca ringens (Lindl.) Schltr. (Orchidaceae: Maxillariinae).

BACKGROUND AND AIMS: Pollination through sexual mimicry, also known as pseudocopulation, has been suggested to occur in some genera of the Neotropical orchid subtribe Maxillariinae. However, it has been demonstrated so far only for Trigonidium obtusum. This study reports and illustrates pollination through sexual mimicry in Mormolyca ringens. METHODS: A total of 70 h were dedicated to the observation of flowers and pollinator behaviour, which was photographically recorded. Flower features involved in pollinator attraction were studied using a stereomicroscope and by SEM analyses. Preliminary observations on the plant breeding system were made by manually self-pollinating flowers. The chemical composition of the fragrance volatiles was determined by GC/MS analysis. KEY RESULTS: The flower features of M. ringens parallel those of other pseudocopulatory flowers. The labellum shape and indument are reminiscent of an insect. Sexually excited drones of Nannotrigona testaceicornis and Scaptotrigona sp. (both in the Apidae: Meliponini) attempt copulation with the labellum and pollinate the flower in the process. In both bee species, the pollinarium is attached to the scutellum. Pollinator behaviour may promote some degree of self-pollination, but preliminary observations indicate that M. ringens flowers are self-incompatible. Flowers are produced all the year round, which ties in with the production of bee males several times a year. The phylogenetic relationships of M. ringens are discussed and a number of morphological and phenological features supporting them are reported. CONCLUSIONS: It is expected that further research could bring to light whether other Maxillariinae species are also pollinated through sexual mimicry. When a definitive and robust phylogeny of this subtribe is available, it should be possible to determine how many times pseudocopulation evolved and its possible evolutionary history.

Floral resin of Tovomitopsis saldanhae (Guttiferae) and 7-epi-nemorosone: structural revision.

The floral resin of Tovomitopsis saldanhae (Guttiferae) is composed of poliisoprenylated benzophenone and the major constituent is 7-epi-nemorosone which has now been revised.