Tribe Orchideae Research Articles

Phylogenetic position and plastid genome structure of Vietorchis, a mycoheterotrophic genus of Orchidaceae (subtribe Orchidinae) endemic to Vietnam

The orchid genus Vietorchis comprises three species, all discovered in the 21 century. Each of these species is achlorophyllous, mycoheterotrophic and is known to be endemic to Vietnam. The type species of the genus, V. aurea, occurs in a single location in northern Vietnam within a lowland limestone karstic area. Vietorchis furcata and V. proboscidea, in contrast, are confined to mountains of southern Vietnam, far away from any limestone formations. Taxonomic placement of Vietorchis remained uncertain for the reason of inconclusive morphological affinities. At the same time, the genus has never been included into molecular phylogenetic studies. We investigate the phylogenetic relationships of two species of Vietorchis (V. aurea and V. furcata) based on three DNA datasets: (1) a dataset comprising two nuclear regions, (2) a dataset comprising two plastid regions, and (3) a dataset employing data on the entire plastid genomes. Our phylogenetic reconstructions support the placement of Vietorchis into the subtribe Orchidinae (tribe Orchideae, subfamily Orchidoideae). This leads to a conclusion that the previously highlighted similarities in the rhizome morphology between Vietorchis and certain mycoheterotrophic genera of the subfamilies Epidendroideae and Vanilloideae are examples of a convergence. Vietorchis is deeply nested within Orchidinae, and therefore the subtribe Vietorchidinae is to be treated as a synonym of Orchidinae. In the obtained phylogenetic reconstructions, Vietorchis is sister to the photosynthetic genus Sirindhornia. Sirindhornia is restricted to limestone mountains, which allows to speculate that association with limestone karst is plesiomorphic for Vietorchis. Flower morphology is concordant with the molecular data in placing Vietorchis into Orchidinae and strongly supports the assignment of the genus to one of the two major clades within this subtribe. Within this clade, however, Vietorchis shows no close structural similarity with any of its genera; in particular, the proximity between Vietorchis and Sirindhornia has never been proposed. Finally, we assembled the plastid genome of V. furcata, which is 65969 bp long and contains 45 unique genes, being one of the most reduced plastomes in the subfamily Orchidoideae. The plastome of Vietorchis lacks any rearrangements in comparison with the closest studied autotrophic species, and possesses substantially contracted inverted repeats. No signs of positive selection acting on the protein-coding plastid sequences were detected.

Notes on an endemic genus <i>Odisha</i> (Orchidaceae) and its two subspecies from Odisha, India

The present communication reinstate the genus Odisha S. Misra and the subspecies Odisha cleistantha subsp. cleistantha (Subtribe Odishinae: tribe Orchideae: Orchidaceae). An in-depth discussion of the typical characters (which is observed as constant in series of biotypes) of the genus Odisha has also been provided here to counter for its erroneous merger in the genus Habenaria Willd. based on characters of secondary importance. Comparative illustrations have also been provided in support of our finding revealed from study of a large number of biotypes from Odisha state, India. A key to both the subspecies of Odisha cleistantha i.e., Odisha cleistantha subsp. cleistantha and subsp. flabellata has been also given here.

The complete chloroplast genome sequence of Dactylorhiza majalis (Rchb.) P.F. Hunt et Summerh. (Orchidaceae)

The complete chloroplast genome of Dactylorhiza majalis (Rchb.) P.F. Hunt et Summerh. (Orchidaceae:Orchidoideae) was assembled and characterized using next-generation sequencing data. The plastome (154,108 bp) possesses the typical circular structure consisting of a large single-copy region (LSC; 83,196 bp), a small single-copy region (SSC; 26,580 bp), and two copies of inverted repeats (17,752 bp each). Its overall GC content is 36.99% and the plastome encodes 134 genes. Reconstruction of phylogenetic relationships using complete plastome sequences of Orchidaceae representatives showed that D. majalis was nested within the Orchidoideae tribe Orchideae. The complete plastome comprises a valuable tool in elucidating taxonomic uncertainties within the genus Dactylorhiza.

Spontaneous caudicle reconfiguration in Dactylorhiza fuchsii: A new self-pollination mechanism for Orchideae

Deceptive plants represent a strategy that promotes outcrossing and protects against facilitated selfing. However, deception does not eliminate the possibility of autonomous self-pollination when pollinators are scarce or absent. Spontaneous autogamy is widespread in Orchidaceae, but the scale, mechanism, time of appearance and effectiveness remain underestimated. Using field and laboratory observations and experiments, for the first time, we documented the possibility of autonomous self-pollination in the deceptive orchid Dactylorhiza fuchsii, which might occur through the previously unspecified mechanism in the tribe Orchideae of caudicle reconfiguration. Self-pollination occurred through the pollinarium twisting to the side and downwards, which was different than caudicle bending forward on the body of pollinators. Caudicle reconfiguration was continuously distributed during anthesis and was common in the studied populations. This mechanism was independent on the flower position in the inflorescence, but was sensitive to pollinator activity. (The frequency of caudicle reconfiguration increased when more pollinaria in the inflorescence were untouched.) This process was effective (self-pollination leading to autogamous fruits and seeds) only when a full caudicle rotation occurred and the pollinium touched the stigma. However, most caudicle reconfigurations were completed before the stigma was reached, resulting in less than 1% of autogamous pollination in the studied populations.

The complete plastome sequence of the endangered orchid Habenaria radiata (Orchidaceae)

In this study, we determined the complete chloroplast sequence of Habenaria radiata (Thunb.) Spreng. (Orchidaceae) (NCBI acc. no. KX871237), an endangered plant species protected by the national law of Korea. The gene order and gene content of the H. radiata plastome are similar to those of typical angiosperm plastomes. The 11 ndh genes, which are usually lost in orchid plastomes, are intact in the H. radiata plastome. The complete plastome is 155,353 bp in length and consists of a large single copy of 84,833 bp and a small single copy of 17,718 bp, separated by two inverted repeats of 26,401 bp. The plastome contains 113 genes, of which 79 are protein-coding genes, 30 are tRNA genes, and four are rRNA genes. Sixteen genes contain one intron and two genes (clpP, ycf3) have two introns. A total of 76 simple sequence repeat (SSR) loci, which consist of 58 mono-SSR, 17 di-SSR, and 1 tri-SSR, are scattered along the H. radiata plastome. Some of these plastome SSR and high sequence divergent regions may be useful for development of genetic markers for the populations of H. radiata and other congeneric species. Phylogenetic analysis identified the sister relationship between H. radiata and H. pantlingiana within the tribe Orchideae.

Phylogenetics of tribe Orchideae (Orchidaceae: Orchidoideae) based on combined DNA matrices: inferences regarding timing of diversification and evolution of pollination syndromes

Tribe Orchideae (Orchidaceae: Orchidoideae) comprises around 62 mostly terrestrial genera, which are well represented in the Northern Temperate Zone and less frequently in tropical areas of both the Old and New Worlds. Phylogenetic relationships within this tribe have been studied previously using only nuclear ribosomal DNA (nuclear ribosomal internal transcribed spacer, nrITS). However, different parts of the phylogenetic tree in these analyses were weakly supported, and integrating information from different plant genomes is clearly necessary in orchids, where reticulate evolution events are putatively common. The aims of this study were to: (1) obtain a well-supported and dated phylogenetic hypothesis for tribe Orchideae, (ii) assess appropriateness of recent nomenclatural changes in this tribe in the last decade, (3) detect possible examples of reticulate evolution and (4) analyse in a temporal context evolutionary trends for subtribe Orchidinae with special emphasis on pollination systems. The analyses included 118 samples, belonging to 103 species and 25 genera, for three DNA regions (nrITS, mitochondrial cox1 intron and plastid rpl16 intron). Bayesian and maximum-parsimony methods were used to construct a well-supported and dated tree. Evolutionary trends in the subtribe were analysed using Bayesian and maximum-likelihood methods of character evolution. The dated phylogenetic tree strongly supported the recently recircumscribed generic concepts of Bateman and collaborators. Moreover, it was found that Orchidinae have diversified in the Mediterranean basin during the last 15 million years, and one potential example of reticulate evolution in the subtribe was identified. In Orchidinae, pollination systems have shifted on numerous occasions during the last 23 million years. The results indicate that ancestral Orchidinae were hymenopteran-pollinated, food-deceptive plants and that these traits have been dominant throughout the evolutionary history of the subtribe in the Mediterranean. Evidence was also obtained that the onset of sexual deception might be linked to an increase in labellum size, and the possibility is discussed that diversification in Orchidinae developed in parallel with diversification of bees and wasps from the Miocene onwards.

Contribution of mitochondrial cox1 intron sequences to the phylogenetics of tribe Orchideae (Orchidaceae): Do the distribution and sequence of this intron in orchids also tell us something about its evolution?

AbstractIn this paper, we use the mitochondrial region cox1 to assess the usefulness of this marker in addressing evolutionary relationships within the tribe Orchideae. Despite the low overall variation uncovered in this region, one good phylogenetic marker was identified. A large group I intron was shared across subtribe Orchidinae and some species of Habenariinae sensu Dressler. The clades identified in the cox1 tree were weakly supported, but consistent with previous studies based on nuclear ribosomal spacers (nrITS). Moreover, the phylogenetic analysis of the combined cox1/ITS data matrix allowed us to highly improve the resolution of the ITS‐only analysis and confirm several previously controversial relationships. A second purpose of this study was to analyse the evolution of the group I cox1 intron in Orchideae. This intron has a patchy distribution in angiosperms that has been claimed to be mostly due to horizontal transfer events. Our results suggest that, despite the differences observed in the co‐conversion tracts in the tribe, vertical transfer is more consistent with the observed phylogenetic trees.

The gynostemium of Hemipiliopsis purpureopunctata and Senghasiella glaucifolia, two taxonomically disputed species of Habenariinae (Orchidaceae)

The gynostemium structure and ontogeny of two taxonomically disputed orchids, Hemipiliopsis (= Habenaria) purpureopunctata and Senghasiella (= Habenaria) glaucifolia, are described and illustrated by scanning electron micrographs. The early gynostemium ontogeny of Hemipiliopsis purpureopunctata is shown to be fundamentally similar to that of the species of the tribe Orchideae that have been previously studied. This includes the initiation sequence of sepals, petals and lip, form and orientation of anthers, three-lobed condition of median carpel apex, and presence of auricles and basal bulges. During the later developmental stages some differences occur. The stigma processes of Senghasiella glaucifolia are united into a tongue-shaped organ, and the lateral rostellum lobes of Hemipiliopsis purpureopunctata protrude forwards with their viscidia positioned above the spur-mouth. Based on gynostemium characters, the generic rank of Hemipiliopsis was confirmed, but that of Senghasiella was not supported. © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society, 2005, 147, 191‐196. ADDITIONAL KEYWORDS: generic rank ‐ Habenaria ‐ ontogeny ‐ Orchideae.

Cytological studies on some representative species of the tribe Orchideae (Orchidaceae) from China

Cytological studies were carried out on 14 taxa belonging to Amitostigma, Chusua, Galearis, Habenaria, Hemipilia, Hemipiliopsis, Herminium, Peristylus and Ponerochis, collected mostly from the south-eastern part of the Hengduan Mountain Region, south-west China. Cytological data on 11 of the taxa are reported for the first time. The interphase nuclei were either of the simple chromocentre type or intermediate between simple and complex chromocentre types. The nuclear morphology of Hemipiliopsis at interphase supports the conclusion that it is related more closely to Chusua and Ponerochis than to Habenaria. At the whole tribe level, however, the results did not indicate a clear correlation between morphological features of the interphase nuclei and phylogeny. The somatic chromosome numbers were 2n = 42 in ten species and 2n = 32, 38, 40, 64 and 72 in four species. The chromosome counts of 2n = 32 and 64 in Habenaria aitchsonii are rare in the genus. It is proposed that the repeated change of chromosome number from x = 7 to x = 8 has played an important role in the evolution of the tribe Orchideae. This change has occurred mainly in the European subtribe Orchidinae, but also in the Asian subtribe Habenariinae. © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society, 2004, 145, 231–238.

Molecular phylogenetics and evolution of Orchidinae and selected Habenariinae (Orchidaceae)

Internal transcribed spacer (ITS nuclear rDNA) data have been obtained from 190 terrestrial orchid species, encompassing all genera and the great majority of the widely recognized species of Orchidinae, a heterogeneous selection of species of Habenariinae, and single species of Satyriinae and Disinae (the latter serving as outgroup). The resulting parsimony-based phylogeny reveals 12 well-resolved clades within the Orchidinae, based on Anacamptis s.l., Serapias, Ophrys, Steveniella–Himantoglossum s.l. (including ‘Comperia’ and ‘Barlia’, most species being 2n = 36), Neotinea s.l., Traunsteinera–Chamorchis, Orchis s.s., Pseudorchis–Amerorchis–Galearis–Neolindleya–Platanthera s.l. (most 2n = 42), Dactylorhiza s.l., Gymnadenia s.l. (most 2n = 40, 80), Ponerorchis s.l.–Hemipilia s.l.–Amitostigma–Neottianthe, and Brachycorythis (most 2n = 42). Relationships are less clearly resolved among these 12 clades, as are those within Habenariinae; the subtribe appears either weakly supported as monophyletic or as paraphyletic under maximum parsimony, and the species-rich genus Habenaria is clearly highly polyphyletic. The triphyly of Orchis as previously delimited is confirmed, and the improved sampling allows further generic transfers to Anacamptis s.l. and Neotinea s.l. In addition, justifications are given for: (1) establishing Steveniella as the basally divergent member of an appreciably expanded Himantoglossum that incorporates the former genera ‘Barlia’ and ‘Comperia’, (2) reuniting ‘Piperia’ with a broadly defined Platanthera as section Piperia, necessitating ten new combinations, (3) broadening Ponerorchis to include Chusua, and Hemipilia to include single ‘orphan’ species of Ponerorchis and Habenaria, and (4) recognizing ‘Gymnadenia’camtschatica as the monotypic Neolindleya camtschatica within the Pseudorchis∼Platanthera clade. Few further generic transfers are likely in Orchidinae s.s., but they are anticipated among habenariid genera, on acquisition of additional morphological and molecular evidence; one probable outcome is expansion of Herminium. Species-level relationships are also satisfactorily resolved within most of the major clades of Orchidinae, with the notable exceptions of Serapias, the derived sections of Ophrys, Himantoglossum s.s., some sections within Dactylorhiza, the former genus ‘Nigritella’ (now tentatively placed within Gymnadenia s.l.), Hemipilia s.l., and possibly Ponerorchis s.s. Relationships among the 12 major clades broadly accord with bona fide records of intergeneric hybridization. Current evidence supports the recently recognized 2n = 36 clade; it also indicates a 2n = 40 clade that is further diagnosed by digitate root-tubers, and is derived relative to the recently recognized clade of exclusively Asian genera (Ponerorchis s.l.–Hemipilia s.l.–Amitostigma–Neottianthe). This in turn appears derived relative to the Afro-Asiatic Brachycorythis group; together, these two clades identify the plesiomorphic chromosome number as 2n = 42. If the African genus Stenogolottis is correctly placed as basally divergent within a monophyletic Habenariinae, the tribe Orchideae and subtribes Orchidinae and Habenariinae could all have originated in Africa, though in contrast the Asiatic focus of the basally divergent members of most major clades of Orchidinae suggests an Asiatic radiation of the subtribe. Morphological characters informally ‘mapped’ across the molecular phylogeny and showing appreciable levels of homoplasy include floral and vegetative pigmentation, flower shape, leaf posture, gynostemium features, and various pollinator attractants. Qualitative comparison of, and reciprocal illumination between, degrees of sequence and morphological divergence suggests a nested set of radiations of progressively decreasing phenotypic magnitude. Brief scenarios, both adaptive and non-adaptive, are outlined for specific evolutionary transitions. Recommendations are made for further species sampling, concentrating on Asian Orchidinae (together with the Afro-Asiatic Brachycorythis group) and both Asian and Southern Hemisphere Habenariinae, and adding plastid sequence data. Taxonomic changes listed are: Anacamptis robusta (T.Stephenson) R.M.Bateman, comb. nov., A. fragrans (Pollini) R.M.Bateman, comb. nov., A. picta (Loiseleur) R.M.Bateman, comb. nov., Neotinea commutata (Todari) R.M.Bateman, comb. nov., N. conica (Willdenow) R.M.Bateman, comb. nov., Platanthera elegans Lindley ssp. maritima (Rydberg) R.M.Bateman, comb. nov., P. elegans Lindley ssp. decurtata (R.Morgan & Glicenstein) R.M.Bateman, comb. nov., P. elongata (Rydberg) R.M.Bateman, comb. nov., P. michaelii (Greene) R.M.Bateman, comb. nov., P. leptopetala (Rydberg) R.M.Bateman, comb. nov., P. transversa (Suksdorf) R.M.Bateman, comb. nov., P. cooperi (S.Watson) R.M.Bateman, comb. nov., P. colemanii (R.Morgan & Glicenstein) R.M.Bateman, comb. nov., P. candida (R.Morgan & Ackerman) R.M.Bateman, comb. nov. and P. yadonii (R.Morgan & Ackerman) R.M.Bateman, comb. nov. © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society, 2003, 142, 1–40.

NOTES RELATING TO THE FLORA OF BHUTAN: XLIV. TAXONOMICNOTES, NEW TAXA AND ADDITIONS TO THE ORCHIDACEAE OF BHUTAN AND SIKKIM (INDIA)

The terrestrial orchid genus Bhutanthera Renz (subfamily Orchidoideae, tribe Orchideae), comprising five species, three newly described here, is established. A new species, Herminium pygmaeum Renz, and three new varieties, Bulbophyllum cauliflorum Hook.f. var. sikkimense N. Pearce & P. J. Cribb, Cephalanthera erecta (Thunb.) Bl. var. oblanceolata N. Pearce & P. J. Cribb, and Gymnadenia orchidis Lindl. var. pantlingii Renz, are here newly described. Five new combinations and one new name are proposed. Four new sections of Bulbophyllum are also established and their relationships discussed.

Pollen morphology of the Diseae (Orchidoideae; Orchidaceae)

Abstract The pollen morphology of 8 species (TEM) and 85 species (SEM) of the tribe Diseae (Disinae, Satyriinae, Coryciinae), and its related tribe Orchideae, is described. It is shown that pollen tetrads are calymmate, but the massulae and pollinia are acalymmate. Pollen cohesion is also established by means of tectal bridges. Three layers of the pollen wall were observed: ektexine, exintine and endintine. Pollen characters were analysed using cladistic methods and assessed in relation to the present phylogeny of the group. Pollen data served to resolve taxa at the subtribal level and provided evidence of relationship for taxonomically problematic taxa. The Coryciinae sensu stricto are palynologically defined by a suite of synapomorphies, including a secondarily tectate exine structure, fasciculate massulae and elongated tetrads with linear microspore configuration. The Disinae can be weakly grouped on the basis of rugose or verrucose pollen surfaces. Results suggest that Brownleea is incorrectly grouped...

Floral morphology of southern African Orchideae. II. Habenariinae

The floral morphology of the southern African genera of Orchideae‐Habenariinae (Bonatea, Cynorkis, Habenaria, Platycoryne, Stenoglottis, Centrostigma and Roe‐perocharis) is surveyed paying special attention to the gynostemium. Ontogenetic data are provided for the species from which adequate material was available. It is shown that the floral architecture is essentially an elaboration and complication of that found in the better known Orchidinae. The structural similarities are particularly evident in the early ontogeny. Although the tribe Orchideae is commonly said to have gynostemia with erect anthers, a few Habenariinae are reported here to have reflexed anthers. In most cases both ‘auricles’ (filament excrescences) and ‘basal bulges’ (staminodes) are united to form the lateral gynostemium appendages. The primordia of both structures are clearly recognizable in the early ontogeny in all species studied. In Habenaria dregeana the basal bulges are only basally fused to the auricles, but in their main portion become adnate to the lip and petal bases: the auricles then solely form the lateral gynostemium appendages. It is suspected that this occurs also in other species not studied here. Systematic and phylogenetic aspects of the southern African representatives of the Habenariinae are discussed: the generic separation of Bonatea, Platycoryne and Centrostigma from Habenaria does not appear justified. Cynorkis, Roeperocharis and Stenoglottis are morphologically dissimilar to Habenaria. Based on the findings in the southern African taxa the status of the Habenariinae, Orchidinae, Orchideae and Diseae is discussed: there is no clear distinction between Habenariinae and Orchidinae; while the Diseae seem to represent a monophyletic group, the Orchideae are possibly polyphyletic.

Floral morphology and ontogeny in Orchidaceae subtribe Disinae

Floral morphology and ontogeny in Orchidaceae subtribe Disinae. The flower structure and development of 24 species of the orchid subtribe Disinae are described and illustrated by drawings and scanning electron micrographs with special attention being paid to the gynostemium. The morphogenesis of this subtribe is fundamentally similar to that of the closely related tribe Orchideae. This includes the initiation of the auricles on the anther base in a dorsolateral position, and hence their interpretation as being mere appendages of the filament. The keel connecting the petals and the gynostemium plus its protrusion is considered homologous to the inner lateral staminodeS. Presumed vestiges of the adaxial staminodes were detected in one specieS. A peculiarity of the Disinae is that the entire apex of the median carpel develops into the rostellum, whereas its stigmatic portion emerges from the median carpel below the rostellum in later stages. The main diagnostic feature of the group is the reflexed position of the mature anther. However, it is shown here that this anther movement occurs in the later stages and that the initial anther is erect.

Developmental studies in orchid flowers II: Orchidoid species

The floral development of 11 species of Orchidoideae (sensu Rasmussen 1985) was studied by means of SEM, paying special attention to the early development of the gynostemium and its appendages. In contrast to the staminodes found in epidendroid and vandoid orchids, the ‘auricles’ of the tribe Orchideae are developed on the dorsal side of the fertile anther and therefore are not interpreted as staminodes. Presumed vestiges of the staminodes corresponding to those of the Epidendroideae and Vandoideae are differentiated in early developmental stages, but remain inconspicuous structures later on. The three‐lobed rostellum originates entirely from the median carpel. The outstanding systematic position of the tribe Orchideae is briefly discussed.

The Development and Mobilisation of Seed Reserves in Some African Orchids

The development, final appearance and digestion (during germination) of seed reserves in a number of genera of the Orchidaceae (tribe Orchideae) has been studied comprehensively, using ultrastructural and histochemical techniques complemented by gas chromatographic analysis of free sugars. Mature seeds of Disa, Disperis and Huttonaea contain substantial reserves of lipid and protein in the embryo. The protodermal cells of Disperis also contain protein-carbohydrate bodies. Free sugars are present but starch occurs only in immature seeds. Glyoxysomes are absent and lipolysis does not occur in seeds incubated without an external source of sucrose, and although a little starch is formed it is apparently synthesised from endogenous sucrose reserves. In the presence of exogenous sucrose, however, proteins are hydrolysed and glyoxysomes appear. Substantial quantities of starch are formed in such seeds. From these observations it is apparent that orchid seeds are unable to utilise endogenous reserves of lipid unless simple sugars are supplied to the medium but can utilise the free sugars present in the embryo. Resultant conclusions on the role of mycorrhizae in the germination of orchid seeds are discussed.

African Orchids: XXXII

During the preparation of the first part of the Orchidaceae for the 'Flora of Tropical East Africa', that dealing with the tribe Orchideae only, it was decided to include a conspectus of the larger genera such as Habenaria. This necessitated a considerable amount of investigation at sectional level and much of this has already been published by V. S. Summerhayes in this series of papers on African Orchids in the 'Kew Bulletin' and elsewhere. The following notes will complete the picture as far as East African Habenaria is concerned, but it must be emphasized that work on a world-wide monographic scale would almost certainly alter the names of some of the sections known to occur in Africa.