Resupinate Flowers Research Articles

Incomplete resupination during floral development leads to pollination failure in a slipper orchid.

In many families, plants undergo floral resupination by twisting through approximately 180° during floral development so that the flower is effectively positioned upside down. In most orchids, resupination results in the median petal (i.e., the labellum) becoming lowermost, which plays a crucial role in pollination by serving as a landing platform or as a trapping device, or both. Incomplete resupination is predicted to lead to reduced pollination, although tests of this assumption are still lacking. We investigated the effect of resupination using Phragmipedium vittatum, a rare lady's slipper orchid whose specialized labellum forms a trapping device. First, we surveyed the natural occurrence of incomplete resupination. Then we manipulated flowers into non- (≈0°), half- (≈90°), and fully resupinate (≈180°) positions to test the effect of orientation on pollen smear removal and deposition by pollinators (female hoverflies). We found that ca. 10% of flowers in the natural population were not fully resupinate, being either non- (upward, 0-60°) or half-resupinate (sideward, 60-120°). The change in orientation prevented the effectiveness of pollination by hoverflies since no pollen smear removal or deposition were found in flowers from non- and half-resupinate treatments. Although these flowers still attracted hoverflies, they were not trapped effectively. As this orchid is incapable of autonomous self-pollination, flowers that do not resupinate fail to set fruits. These results highlight the importance of correct floral orientation provided by resupination to ensure pollination in orchids and other resupinate flowers.

A new species of Triphora (Orchidaceae: Triphoreae, Triphorinae) from Mexico

Triphora gallegosii, a new species of geophyte orchid known so far from central, western, and northwestern Mexico, is described and illustrated. This species is morphologically similar to T. gentianioides and T. wagneri, with whom it shares the presence of scale-like leaves, three longitudinal verrucose lines on the lip, and floral parts of similar sizes, but differs from both by its lip lines that vanish towards the middle of the central lobe, having 1–4 resupinate flowers, and flowering between August and September. It also differs from T. wagneri by having a constricted central lobe and lateral lobes with acute apex, and from T. gentianoides by having entire margins on the lateral lobes, column with a magenta apex and whitish towards the middle portion with a green base, magenta anther, smaller leaves, and solitary growth. A preliminary analysis of the conservation status and a dichotomous key to the species of the genus in Mexico are provided.

Epidendrum alejandrinae (Orchidaceae: Laeliinae), a new species from the high Andean forests of central Peru

The high Andean forests harbor great and unique biodiversity. Here, we report a new species of Epidendrum from Peru. Epidendrum alejandrinae is described, illustrated and compared with the morphologically similar Epidendrum ochoae, Epidendrum pachydiscum and Epidendrum aida-alvareziae. We performed a systematic review of herbarium information on the species reported for the Region of Huancavelica and compared the morphological features of the closest species to rule out possible matches. The new species is characterized by a short, foliate aggregate stems, an apical pendulous inflorescence formed from the stem, green resupinate flowers opening in succession, the petals and sepals semi-extended, a 3-lobed lip, lateral lobes obliquely ovoid, median lobe broadly cuneate, bicallose, and four, obovoid, laterally compressed pollinia. The novelty represents an important record for the flora associated with the high Andean forest dominated by Polylepis and Gynoxys in central Peru.

Duplication and expression patterns of CYCLOIDEA-like genes in Campanulaceae

BackgroundCYCLOIDEA (CYC)-like transcription factors pattern floral symmetry in most angiosperms. In core eudicots, two duplications led to three clades of CYC-like genes: CYC1, CYC2, and CYC3, with orthologs of the CYC2 clade restricting expression dorsally in bilaterally symmetrical flowers. Limited data from CYC3 suggest that they also play a role in flower symmetry in some asterids. We examine the evolution of these genes in Campanulaceae, a group that contains broad transitions between radial and bilateral floral symmetry and 180° resupination (turning upside-down by twisting pedicle).ResultsWe identify here all three paralogous CYC-like clades across Campanulaceae. Similar to other core eudicots, we show that CamCYC2 duplicated near the time of the divergence of the bilaterally symmetrical and resupinate Lobelioideae. However, in non-resupinate, bilaterally symmetrical Cyphioideae, CamCYC2 appears to have been lost and CamCYC3 duplicated, suggesting a novel genetic basis for bilateral symmetry in Cyphioideae. We additionally, utilized qRT-PCR to examine the correlation between CYC-like gene expression and shifts in flower morphology in four species of Lobelioideae. As expected, CamCYC2 gene expression was dorsoventrally restricted in bilateral symmetrical flowers. However, because Lobelioideae have resupinate flowers, both CamCYC2A and CamCYC2B are highly expressed in the finally positioned ventral petal lobes, corresponding to the adaxial side of the flower relative to meristem orientation.ConclusionsOur sequences across Campanulaceae of all three of these paralogous groups suggests that radially symmetrical Campanuloideae duplicated CYC1, Lobelioideae duplicated CYC2 and lost CYC3 early in their divergence, and that Cyphioideae lost CYC2 and duplicated CYC3. This suggests a dynamic pattern of duplication and loss of major floral patterning genes in this group and highlights the first case of a loss of CYC2 in a bilaterally symmetrical group. We illustrate here that CYC expression is conserved along the dorsoventral axis of the flower even as it turns upside-down, suggesting that at least late CYC expression is not regulated by extrinsic factors such as gravity. We additionally show that while the pattern of dorsoventral expression of each paralog remains the same, CamCYC2A is more dominant in species with shorter relative finally positioned dorsal lobes, and CamCYC2B is more dominant in species with long dorsal lobes.

Systematics of Lobelioideae (Campanulaceae): review, phylogenetic and biogeographic analyses.

Lobelioideae, the largest subfamily within Campanulaceae, includes 33 genera and approximately1200 species. It is characterized by resupinate flowers with zygomorphic corollas and connate anthers and is widely distributed across the world. The systematics of Lobelioideae has been quite challenging over the years, with different scholars postulating varying theories. To outline major progress and highlight the existing systematic problems in Lobelioideae, we conducted a literature review on this subfamily. Additionally, we conducted phylogenetic and biogeographic analyses for Lobelioideae using plastids and internal transcribed spacer regions. We found that former studies have reached agreement on the southern African origin of Lobelioideae, herbaceous habit and Asian origin of giant lobelioids, the convergent evolution of giant rosette lobelioids, and lastly, the multiple cosmopolitan and independent radiation of lobelioids in Africa, Pacific Basin, and the Hawaiian Islands. Also, Apetahia Baill., Sclerotheca A.DC., and Cyanea Gaudich. are paraphyletic, while Lobelia L., Pratia Gaudich., Centropogon C.Presl, Siphocampylus Pohl, and Isotoma Lindl. are polyphyletic. The taxonomy of these genera, especially Lobelia, is particularly quite frustrating. This calls for further reappraisals using both morphological and molecular data.

Crocodeilanthe chachapoyensis (Orchidaceae: Pleurothallidinae), a New Species from Amazonas, Peru

Crocodeilanthe chachapoyensis Damian sp. nova (Orchidaceae: Pleurothallidinae), a new species from Amazonas, Peru, is proposed. It is similar in overall morphology to the Ecuadorian C. molleturoi. However, C. chachapoyensis is distinguished by its shorter ramicauls, larger resupinate flowers and 3-lobed, callose-free lip with a pair of cavities above the base. A line drawing and habitat information are provided as well as a comparison with morphologically similar species.

Senyumiagranitica (Gesneriaceae) from Johor, Malaysia, the second species of Senyumia.

The genus Senyumia was previously known from a single species, S.minutiflora (Ridl.) Kiew, A.Weber & B.L.Burtt, from a limestone karst, Gunung Senyum, in Pahang, Malaysia. Senyumiagranitica Kiew, here described and illustrated, is the second species of the genus. It differs from S.minutiflora, not only in its habitat, but also in its shorter leaves, larger, non-resupinate or only partially resupinate flowers and smaller seeds. It is known from a small, fragmented population from a low range of hills. Therefore, under the IUCN Red List Categories & Criteria, it is assessed as Critically Endangered.

Centrosema sericiflorum (Leguminosae, Papilionoideae), a New Species Endemic to the Caatinga of Bahia, Brazil, and a Key to the Bahian Species of the Genus

Centrosema is a genus of the papilionoid legume tribe Phaseoleae (subtribe Clitoriinae) including about 35 species from the Neotropical region, characterized by the resupinate flowers and the standard petal provided with a spur on the outer surface. During a survey of the species from eastern Brazil, in the state of Bahia, a new species was found and is here described and illustrated. Centrosema sericiflorum differs from other species of the genus mainly by the sericeous indumentum of the outer surface of the calyx and the standard petal (vs. puberulous, pubescent, or villous). The new species occurs in semideciduous forests of the Chapada Diamantina mountain range and is only known from a restricted area in Central Bahia. It was informally assessed as Endangered following IUCN criteria because of its restricted range and occurrence in areas cleared for coffee plantation.

Aphyllorchis maliauensis (Orchidaceae), a new species from the Maliau Basin, Sabah, Borneo

Aphyllorchis Blume (1825: 16) comprises approximately 30 species distributed from Sri Lanka, the western Himalayas, and China through Indochina, Malaysia, Indonesia, Taiwan and the Philippines eastward to New Guinea and Australia (Hsieh et al. 2013, Tian et al. 2013). Aphyllorchis species are leafless and mycoheterotrophic, with erect, unbranched stems, racemose inflorescences, multiple resupinate flowers, petals similar to sepals but shorter and narrower and lips divided into hypochile and epichile (Tian et al. 2013). As in most other mycoheterotrophs (Suetsugu 2017, Suetsugu & Nishioka 2017, Suetsugu et al. 2017), the diversity of Aphyllorchis species could be underestimated since the short flowering season and inconspicuous habit make them easily overlooked in the wild (Hsieh et al. 2013).

Description and phylogenetic position of a new species of Nematanthus (Gesneriaceae) from Bahia, Brazil

Abstract Chautems, A. & M. Perret (2017). Description and phylogenetic position of a new species of Nematanthus (Gesneriaceae) from Bahia, Brazil. Candollea 72: 351–359. In English, English abstract. DOI: http://dx.doi.org/10.15553/c2017v722a13 Nematanthus exsertus Chautems, a new species of Gesneriaceae from the state of Bahia in Brazil, is described. It is easily distinguished from other Nematanthus Schrad. species by its pendent resupinate flowers with funnel-shaped and laterally compressed corolla combined with striking exserted stamens and style. According to the phylogenetic analyses based on nuclear and plastid DNA sequences, this species belongs to a clade including the morphologically distinct Nematanthus monanthos (Vell.) Chautems and four other species with a similar flower morphology but lacking exserted stamen and style. Field photographs accompany the description. The new species is known from one locality in the municipality of Wenceslau Guimaraes in the southern part of Bahia state within ...

Transcriptome-Wide Identification and Expression Analysis of DIVARICATA- and RADIALIS-Like Genes of the Mediterranean Orchid Orchis italica.

Bilateral symmetry of flowers is a relevant novelty that has occurred many times throughout the evolution of flowering plants. In Antirrhinum majus, establishment of flower dorso-ventral asymmetry is mainly due to interaction of TCP (CYC and DICH) and MYB (DIV, RAD, and DRIF) transcription factors. In the present study, we characterized 8 DIV-, 4 RAD-, and 2 DRIF-like genes from the transcriptome of Orchis italica, an orchid species with bilaterally symmetric and resupinate flowers. We found a similar number of DIV- and RAD-like genes within the genomes of Phalaenopsis equestris and Dendrobium catenatum orchids. Orchid DIV- and RAD-like proteins share conserved motifs whose distribution reflects their phylogeny and analysis of the genomic organization revealed a single intron containing many traces of transposable elements. Evolutionary analysis has shown that purifying selection acts on the DIV- and RAD-like coding regions in orchids, with relaxation of selective constraints in a branch of the DIV-like genes. Analysis of the expression patterns of DIV- and RAD-like genes in O. italica revealed possible redundant functions for some of them. In the perianth of O. italica, the ortholog of DIV and DRIF of A. majus are expressed in all tissues, whereas RAD is mainly expressed in the outer tepals and lip. These data allow for proposal of an evolutionary conserved model in which the expression of the orthologs of the DIV, RAD, and DRIF genes might be related to establishment of flower bilateral symmetry in the nonmodel orchid species O. italica.

Resupinate Dimorphy, a novel pollination strategy in two-lipped flowers of Eplingiella (Lamiaceae)

This work provides a summary of the typical floral structure of subtribe Hyptidinae (Lamiaceae), in which both style and stamens are declinate within or near the concave anterior corolla lobe. Cross-pollination is facilitated by protandry, acting in conjunction with the explosive release of the stamens and pollen. In contrast, we report that in the three species of the genus Eplingiella we found individuals with either resupinate or non-resupinate flowers, which represents a novel floral dimorphism. In these species of Eplingiella, the style occupies a position towards the posterior corolla lip and opposes the declinate stamens. Thus, in non-resupinate flowers the pollinating bee receives pollen on its ventral side and makes contact with the style on its dorsal side, whereas in resupinate flowers, the bee receives pollen on its dorsal side, and contacts the style on its ventral side. Both floral morphs seem to be required to achieve cross-pollination. In the two populations studied, each of the two morphs is present and in similar proportions, providing a novel means of promoting cross-pollination and reducing selfing. The situation in Eplingiella is compared to some other examples of floral polymorphism, but appears to be a unique pollination strategy, here termed Resupinate Dimorphy.

The phylogeny of Heliconia (Heliconiaceae) and the evolution of floral presentation

Heliconia (Heliconiaceae, order Zingiberales) is among the showiest plants of the Neotropical rainforest and represent a spectacular co-evolutionary radiation with hummingbirds. Despite the attractiveness and ecological importance of many Heliconia, the genus has been the subject of limited molecular phylogenetic studies. We sample seven markers from the plastid and nuclear genomes for 202 samples of Heliconia. This represents ca. 75% of accepted species and includes coverage of all taxonomic subgenera and sections. We date this phylogeny using fossils associated with other families in the Zingiberales; in particular we review and evaluate the Eocene fossil Ensete oregonense. We use this dated phylogenetic framework to evaluate the evolution of two components of flower orientation that are hypothesized to be important for modulating pollinator discrimination and pollen placement: resupination and erect versus pendant inflorescence habit. Our phylogenetic results suggest that the monophyletic Melanesian subgenus Heliconiopsis and a small clade of Ecuadorian species are together the sister group to the rest of Heliconia. Extant diversity of Heliconia originated in the Late Eocene (39Ma) with rapid diversification through the Early Miocene, making it the oldest known clade of hummingbird-pollinated plants. Most described subgenera and sections are not monophyletic, though closely related groups of species, often defined by shared geography, mirror earlier morphological cladistic analyses. Evaluation of changes in resupination and inflorescence habit suggests that these characters are more homoplasious than expected, and this largely explains the non-monophyly of previously circumscribed subgenera, which were based on these characters. We also find strong evidence for the correlated evolution of resupination and inflorescence habit. The correlated model suggests that the most recent common ancestor of all extant Heliconia had resupinate flowers and erect inflorescences. Finally, we note our nearly complete species sampling and dated phylogeny allow for an assessment of taxonomic history in terms of phylogenetic diversity. We find approximately half of the currently recognized species, corresponding to half of the phylogenetic diversity, have been described since 1975, highlighting the continued importance of basic taxonomic research and conservation initiatives to preserve both described and undiscovered species of Heliconia.

Illustrations and studies in Neotropical Orchidaceae. 6. The <em>Lepanthes guatemalensis</em> group (Pleurothallidinae) in Costa Rica

We revise and characterize the group of species close to Lepanthes guatemalensis. The group comprises eight species in Costa Rica. Three new species are described and illustrated. Lepanthes durikaensis is distinguished by the non resupinate flowers, the lateral sepals ovate with the apical tails diverging, the lower lobe of petals lanceolate-subfalcate, up-curved and the pinkish column. Lepanthes leporina is recognized by the resupinate flowers with yellow sepals, faintly suffused with red, the petals violet, the lip orange, the bifid synsepal with the apices of the lateral sepals not forming tails, the lateral sepals subequal to the dorsal sepal, the petals markedly convex with the upper lobe elliptic-lanceolate and the lobes of the lip connivent at apex. Lepanthes sanctiorum is characterized by the small plants less than 1.1 cm tall, the short peduncle less than 10 mm long, the petals as wide as the lip length and the blades of the lip distinctly diverging at apex. All the species are described and illustrated on the basis of Costa Rican material. A key to the species of the group is provided.

Panisea panchaseensis sp. nov. (Orchidaceae) from central Nepal

Panisea panchaseensis Subedi sp. nov. (Orchidaceae) is described as a new species from Nepal. The distinguishing characters, a description, detailed illustrations and photographs are provided. The species is genetically compared to P. tricallosa, and a diagnostic key based on the morphology to all species of Panisea is provided. The genus Panisea (Lindl.) Lindl. (Orchidaceae, Epidendroideae, Coelogyninae) consists of 10 species (Lindley 1830, 1854, Chen 1980, Lund 1987, Gravendeel et al. 2005, Averyanov and Averyanova 2006). These species are distributed from the Indian subcontinent to southeast Asia. The genus is easily recognized by the pseudobulbs consisting of a single internode, convolute or duplicate leaves, terminal inflorescence often produced before growth of the pseudobulbs, resupinate flowers, lip with more or less sigmoidly curved base with completely absent or only small side lobes (this character is its main diagnostic feature within the Coelogyninae), a ‘petaloid’ apex of the column hooded over the anther, and entire stigma. In 2002, the first author came across an interesting specimen of Panisea which was collected from Panchase forest in central Nepal. This species was found in the same habitat zone where Panisea demissa Lindl. commonly occurs. The specimens looked very different in habit and flower morphology compared with P. demissa. However, due to limited flowering material, it was impossible to properly investigate their taxonomic identity. In 2007, additional explorations were carried out in the same area and more flowering specimens were located. A study of herbarium specimens of similar species of Panisea, a detailed literature review and DNA sequencing were carried out to investigate whether the specimens from Panchase forest represented an undescribed species.

Evolution of resupination in Malagasy species of Bulbophyllum (Orchidaceae)

Resupination is the orientation of zygomorphic flowers during development so that the median petal obtains the lowermost position in the mature flower. Despite its evolutionary and ecological significance, resupination has rarely been studied in a phylogenetic context. Ten types of resupination occur among the 210 species of the orchid genus Bulbophyllum on Madagascar. We investigated the evolution of resupination in a representative sample of these species by first reconstructing a combined nrITS and cpDNA phylogeny for a sectional reclassification and then plotting the different types of inflorescence development, which correlated well with main clades. Resupination by apical drooping of the rachis appears to have evolved from apical drooping of the peduncle. Erect inflorescences with resupinate flowers seem to have evolved several times into either erect inflorescences with (partly) non-resupinate flowers or pendulous inflorescences with resupinate flowers.

Phylogenetic relationships and generic boundaries in the Episcieae (Gesneriaceae) inferred from nuclear, chloroplast, and morphological data

AbstractEpiscieae is the most diverse tribe of Gesneriaceae, with 22 genera and over 700 species, or roughly 21% of all Gesneriaceae. The tribe is restricted to the Neotropics and is characterized by axillary flowers derived from a pair–flowered cyme inflorescence by reduction, a three–trace trilacunar node with split lateral bundles, superior ovaries, and with most members having a haploid chromosome number of n = 9 [n = 8 in Codonanthe and Nematanthus]. Most traditionally recognized genera in Episcieae are either known to be non–monophyletic or have not been represented adequately in phylogenetic analyses to test their monophyly. This paper presents phylogenetic analyses utilizing two molecular [the internal transcribed spacer region of 18S–26S nuclear ribosomal DNA (ITS) and the trnH–psbA intergenic spacer for 155 species] and one morphological (99 characters for 120 species) datasets, combined in a total evidence analysis. All traditionally recognized genera of Episcieae except for the monotypic genus Lampadaria are represented. Of the 21 sampled genera in Episcieae, 16 are represented by the generic type species. The genera Glossoloma and Crantzia are segregated from the genus Alloplectus as traditionally recognized. Other genera that are strongly supported as monophyletic include Alsobia, Columnea (with the inclusion of C. dielsii), Corytoplectus, and Episcia. Drymonia is weakly supported and is shown here to be morphologically diverse and in need of further evaluation. Evolution of fruit structure is examined in the context of the phylogenetic results presented here with two previously unreported features that are here referred to as capsules with tardily dehiscent and non–dehiscent endocarps. Three independent origins of resupinate flowers are inferred for Glossoloma, Nematanthus, and Crantzia. Strongly supported clades have centers of diversity in southeastern Brazil (Nematanthus, Codonanthe, Codonanthopsis, and Paradrymonia anisophylla), northern South America (Alloplectus, Drymonia, Columnea, Neomortonia), Central America (Alsobia, Oerstedina, Rufodorsia, Cobananthus), and two clades with diversity in the Guiana Shield [(Paradrymonia, Nautilocalyx, Chrysothemis) and (Lembocarpus, Cremersia, Rhoogeton)]. Neomortonia, a genus of three species, is poorly supported due to conflict among datasets.

A Preliminary Phylogeny of Alloplectus (Gesneriaceae): Implications for the Evolution of Flower Resupination

Monophyly of the neotropical plant genus Alloplectus (Gesneriaceae) was tested using maximum parsimony and maximum likelihood phylogenetic analyses of molecular sequence data from the nuclear ribosomal (nrDNA) internal transcribed spacer region (ITS). As currently circumscribed, Alloplectus is polyphyletic and includes taxa in three different clades. The clade that contains the type species is described as Alloplectus sensu stricto and is characterized by the presence of resupinate flowers. The Alloplectus s.s. clade is weakly supported as the sister-group to Columnea. A separate clade of non- resupinate ''Alloplectus'' species nests within a paraphyletic Drymonia. A third taxon, Alloplectus cristatus, endemic to the Lesser Antilles and northwestern South America, is also resupinate and unresolved in a basal polytomy, removed from the other species of Alloplectus. The fourth taxon, Alloplectus peruvianus, which was originally described as Columnea peruviana ,i s strongly supported as nesting within Columnea. Resupination of flowers is an important feature that has not been previously reported and should be recognized as a morphological synapomorphy for Alloplectus s.s. Within the tribe Episcieae, flower resupination is a convergent feature that is independently derived in the Alloplectus s.s. clade, Alloplectus cristatus, and a clade comprising some Nematanthus species.

Roles of synorganisation, zygomorphy and heterotopy in floral evolution: the gynostemium and labellum of orchids and other lilioid monocots.

A gynostemium, comprising stamen filaments adnate to a syncarpous style, occurs in only threc groups of monocots: the large family Orchidaceae (Asparagales) and two small genera Pauridia (Hypoxidaceae: Asparagales) and Corsia (Corsiaceae, probably in Liliales), all epigynous taxa. Pauridia has actinomorphic (polysymmetric) flowers, whereas those of Corsia and most orchids are strongly zygomorphic (monosymmetric) with a well-differentiated labellum. In Corsia the labellum is formed from the outer median tepal (sepal), whereas in orchids it is formed from the inner median tepal (petal) and is developmentally adaxial (but positionally abaxial in orchids with resupinate flowers). Furthermore, in orchids zygomorphy is also expressed in the stamen whorls, in contrast to Corsia. In Pauridia a complete stamen whorl is suppressed, but the 'lost' outer whorl is fused to the style. The evolution of adnation and zygomorphy are discussed in the context of the existing phylogenetic framework in monocotyledons. An arguably typological classification of floral terata is presented, focusing on three contrasting modes each of peloria and pseudopeloria. Dynamic evolutionary transitions in floral morphology are assigned to recently revised concepts of heterotopy (including homeosis) and heterochrony, seeking patterns that delimit developmental constraints and allow inferences regarding underlying genetic controls. Current evidence suggests that lateral heterotopy is more frequent than acropetal heterotopy, and that full basipetal heterotopy does not occur. Pseudopeloria is more likely to generate a radically altered yet functional perianth, but is also more likely to cause acropetal modification of the gynostemium. These comparisons indicate that there are at least two key genes or sets of genes controlling adnation, adaxial stamen suppression and labellum development in lilioid monocots; at least one is responsible for stamen adnation to the style (i.e. gynostemium formation), and another controls adaxial stamen suppression and adaxial labellum formation in orchids. Stamen adnation to the style may be a product of over-expression of the genes related to epigyny (i.e. a form of hyper-epigyny). If, as seems likely, stamen-style adnation preceded zygomorphy in orchid evolution, then the flowers of Pauridia may closely resemble those of the immediate ancestors of Orchidaceae, although existing molecular phylogenetic data indicate that a sister-group relationship is unlikely. The initial radiation in Orchidaceae can be attributed to the combination of hyper-epigyny, zygomorphy and resupination, but later radiations at lower taxonomic levels that generated the remarkable species richness of subfamilies Orchidoideae and Epidendroideae are more likely to reflect more subtle innovations that directly influence pollinator specificity, such as the development of stalked pollinaria and heavily marked and/or spur-bearing labella.

Evolution and Phylogeny of the Pelexia Alliance (Orchidaceae: Spiranthoideae: Spiranthinae)

The Pelexia alliance is distinguished by a blade-like, truncate rostellum, a viscidium with a sUrface that must be ruptured, and an apical extension on the anther covering the immature viscidium. Pelexia, Sarcoglottis, and Cyclopogon and their sections are treated cladistically. The unique position of the stylar canal entrance above the stigmatic surface in Pelexia and Sarcoglottis is considered specialized. Transfer of Pelexia sect. Potosia is confirmed. Various elements of the alliance appear specialized for different habitats and pollinators. The Pelexia alliance seems to have diverged early in the history of the subtribe. Pelexia Poit. ex Lindley is a member of Spiranthinae (Orchidaceae), a largely terrestrial group characterized by a dorsal erect anther, fascicled roots, inconspicuous staminodia, and resupinate flowers. In Schlechter's (1920) revision of the subtribe, characteristics of the column apex, such as the rostellum and viscidium, were used to segregate the various members into four complexes; these are termed the Spiranthes, Brachystele, Pelexia, and Stenorrhynchos alliances (Balogh 1982). As redefined by Balogh (1982), the Brachystele alliance has a very reduced rostellum that is usually inseparable from the apical viscidium portion; the Pelexia alliance has an elongate, broad, laminar rostellum with an apical viscidium portion; the Spiranthes alliance has a broad laminar rostellum with a centrally located viscidium portion; and the Stenorrhynchos alliance has a subulate, bristlelike rostellum that is ensheathed by the viscidium portion. As distinguished by Schlechter (1920), the Pelexia alliance contained Pelexia, Sarcoglottis Presl, Cyclopogon Presl, Deiregyne Schltr., Gamosepalum Schltr., Schiedeella Schltr., and Eurystyles Wawra. In Balogh (1982) Deiregyne and Gamosepalum were combined and transferred to a separate alliance, Eurystyles was transferred to a separate alliance, and Schiedeella was transferred to the Stenorrhynchos alliance. Evidence cited below favors combining the remaining elements into three genera, Pelexia, Sarcoglottis, and Cyclopogon (including Beadlea Small and Manniella americana C. Schweinf. & Garay). The distinctive rostellum that remains more or less intact after removal of the viscidium portion has proven to be correlated with other character states such as the rupturable viscidium and the presence of an apical extension on the anther that protects the immature viscidium. These structural specializations along with others discussed below provide sufficient basis for an attempt to analyze the group cladistically. MATERIALS AND METHODS Materials used in this study were taken from fluid-preserved flowers on deposit at AMO and in the personal collection of Burns-Balogh. It is important in a study based on column structure to use fluid-preserved or fresh flowers because pressing and drying causes loss in detail of the column structures. For an outgroup, the Pelexia alliance is compared with the typical element of the subtribe, the Spiranthes alliance, as represented by Spiranthes Rich., a genus common in temperate North America and comparatively unspecialized or plesiomorphic in many significant character states. Polarity of characters was based on outgroup comparison (Watrous and Wheeler 1981) in which more general character states are plesiomorphic. The cladogram (fig. 1) was constructed in the most parsimonious manner attempting to minimize the amount of homoplasy. During the present study, the various character states have been found to follow along the generic lines established by Balogh (1982) confirming results that were based on traditional taxonomic methods. In Balogh (1982) no attempt was made to go into detail of each genus or alliance or the evolution of each group. The purpose of this paper is to apply cladistic methods to the Pelexia alliance in order to understand the evolution of the group.