Relationships and evolution of matK in a group of leafless orchids (Corallorhiza and Corallorhizinae; Orchidaceae: Epidendroideae)

Corallorhizinae are a small group of Old and New World temperate orchids of which a core monophyletic group comprises Govenia, Cremastra, Aplectrum, Oreorchis and the leafless Corallorhiza, and which according to phylogenetic analysis of nuclear ITS and plastid matK sequences, are related in this way: (Govenia (Cremastra (Aplectrum (Oreorchis (Corallorhiza))))). This hypothesis is consistent with the progressive deletion of the trnK intron and matK ORF. Frameshift-resulting indels yield a predicted loss of translation for the critical "domain X" region of matK and are evidence that matK is a probable pseudogene in Aplectrum, Oreorchis, and Corallorhiza. Within Corallorhiza, a previous hypothesis based on plastid DNA restriction site analysis is confirmed, with the thickened-labellum C. striata group being sister to the thin-labellum remainder of the genus, within which the circumboreal C. trifida is sister to the remainder, which then comprise two further sister groups: C. maculata + C. bulbosa + C. mertensiana and C. odontorhiza + C. wisteriana. A close relationship between C. striata and the recently described Appalachian C. bentleyi is shown; in particular, C. bentleyi is more closely allied to a southern Mexican population of C. striata than it is to northern North American C. striata populations, suggesting that two lineages, each with Mexican and northern North American populations, exist within the C. striata group.     

The plastid genome of the mycoheterotrophic Corallorhiza striata (Orchidaceae) is in the relatively early stages of degradation

? Premise of the study: Plastid genomes of nonphotosynthetic, mycoheterotrophic plants represent apt systems in which to study effects of relaxed evolutionary constraints. The few mycoheterotrophic angiosperm plastomes sequenced to date display drastic patterns of degradation/reduction relative to those of photosynthetic relatives. The goal of this study was to focus on a mycoheterotrophic orchid hypothesized to be in the "early" stages of plastome degradation, to provide perspective on this process. ? Methods: Short-read sequencing was used to generate a complete plastome sequence for Corallorhiza striata var. vreelandii, a mycoheterotrophic orchid, to investigate the extent of plastome degradation. Patterns of nonsynonymous/synonymous mutations were also assessed, and comparisons were made between Corallorhiza and other heterotrophic plant lineages. ? Key results: Corallorhiza yielded a plastome of 137505 bp, with several photosynthesis-related genes either lost or pseudogenized. Members of all major photosynthesis complexes, except ATP-synthase genes, were affected. "Housekeeping" genes were intact, despite the loss of a single tRNA. Intact photosynthesis genes (excluding atp genes) together displayed elevated nonsynonymous changes, while housekeeping genes did not. ? Conclusions: The Corallorhiza plastome is not drastically reduced in overall size (～6% reduction relative to that of photosynthetic Oncidium), but displays a pattern congruent with a loss of photosynthetic function. Comparing Corallorhiza with other heterotrophs allows some emergent evolutionary patterns to be inferred, but these remain as hypotheses to be tested, especially at lower taxonomic levels, and in lineages illustrating transitions from autotrophy to heterotrophy. The independent, unique processes of plastome modification among mycoheterotrophic lineages illustrate the urgency of their conservation.     

Rangewide analysis of fungal associations in the fully mycoheterotrophic Corallorhiza striata complex (Orchidaceae) reveals extreme specificity on ectomycorrhizal Tomentella (Thelephoraceae) across North America

Fully mycoheterotrophic plants offer a fascinating system for studying phylogenetic associations and dynamics of symbiotic specificity between hosts and parasites. These plants frequently parasitize mutualistic mycorrhizal symbioses between fungi and trees. Corallorhiza striata is a fully mycoheterotrophic, North American orchid distributed from Mexico to Canada, but the full extent of its fungal associations and specificity is unknown. Plastid DNA (orchids) and ITS (fungi) were sequenced for 107 individuals from 42 populations across North America to identify C. striata mycobionts and test hypotheses on fungal host specificity. Four largely allopatric orchid plastid clades were recovered, and all fungal sequences were most similar to ectomycorrhizal Tomentella (Thelephoraceae), nearly all to T. fuscocinerea. Orchid-fungal gene trees were incongruent but nonindependent; orchid clades associated with divergent sets of fungi, with a clade of Californian orchids subspecialized toward a narrow Tomentella fuscocinerea clade. Both geography and orchid clades were important determinants of fungal association, following a geographic mosaic model of specificity on Tomentella fungi. These findings corroborate patterns described in other fully mycoheterotrophic orchids and monotropes, represent one of the most extensive plant-fungal genetic investigations of fully mycoheterotrophic plants, and have conservation implications for the >400 plant species engaging in this trophic strategy worldwide.     

Genome size and karyotype evolution in the slipper orchids (Cypripedioideae: Orchidaceae)

Nuclear DNA contents (4C) were estimated by Feulgen microdensitometry in 27 species of slipper orchids. These data and recent information concerning the molecular systematics of Cypripedioideae allow an interesting re-evaluation of karyotype and genome size variation among slipper orchids in a phylogenetic context. DNA amounts differed 5.7-fold, from 24.4 pg in Phragmipedium longifolium to 138.1 pg in Paphiopedilum wardii. The most derived clades of the conduplicate-leaved slipper orchids have undergone a radical process of genome fragmentation that is most parsimoniously explained by Robertsonian changes involving centric fission. This process seems to have occurred independently of genome size variation. However, it may reflect environmental or selective pressures favoring higher numbers of linkage groups in the karyotype.     

High mycorrhizal specificity in a widespread mycoheterotrophic plant, Eulophia zollingeri (Orchidaceae)

Because mycoheterotrophic plants fully depend on their mycorrhizal partner for their carbon supply, the major limiting factor for the geographic distribution of these plants may be the presence of their mycorrhizal partner. Although this factor may seem to be a disadvantage for increasing geographic distribution, widespread mycoheterotrophic species nonetheless exist. The mechanism causing the wide distribution of some mycoheterotrophic species is, however, seldom discussed. We identified the mycorrhizal partner of a widespread mycoheterotrophic orchid, Eulophia zollingeri, using 12 individuals from seven populations in Japan, Myanmar, and Taiwan by DNA-based methods. All fungal ITS sequences from the roots closely related to those of Psathyrella candolleana (Coprinaceae) from GenBank accessions and herbarium specimens. These results indicate that E. zollingeri is exclusively associated with the P. candolleana species group. Further, the molecular data support the wide distribution and wide-ranging habitat of this fungal partner. Our data provide evidence that a mycoheterotrophic plant can achieve a wide distribution, even though it has a high mycorrhizal specificity, if its fungal partner is widely distributed.     

Phylogenetics and biogeography of Mascarene angraecoid orchids (Vandeae, Orchidaceae)

The large angraecoid orchid clade (subtribe Angraecinae sensu lato) has undergone extensive radiation in the western Indian Ocean, which includes Africa, Madagascar, and a number of Indian Ocean islands, such as the Mascarene Archipelago. To investigate systematics and biogeography of these Mascarene orchids, phylogenetic relationships were inferred from four plastid DNA regions, trnL intron, trnL-F intergenic spacer, matK gene, and rps16 intron. Parsimony and Bayesian analyses provided identical sets of relationships within the subtribe; the large genus Angraecum as currently circumscribed does not form an exclusive clade. Bonniera, an endemic genus to Reunion, is shown to be embedded in part of Angraecum. Evidence from our research supports the main origin of Mascarene Angraecinae from Madagascar, and although there were many independent colonizations, only a few of the lineages radiated within the Mascarene Archipelago.     

Mycorrhizal specificity in the fully mycoheterotrophic Hexalectris Raf. (Orchidaceae: Epidendroideae)

Mycoheterotrophic species have abandoned an autotrophic lifestyle and obtain carbon exclusively from mycorrhizal fungi. Although these species have evolved independently in many plant families, such events have occurred most often in the Orchidaceae, resulting in the highest concentration of these species in the tracheophytes. Studies of mycoheterotrophic species' mycobionts have generally revealed extreme levels of mycorrhizal specialization, suggesting that this system is ideal for studying the evolution of mycorrhizal associations. However, these studies have often investigated single or few, often unrelated, species without consideration of their phylogenetic relationships. Herein, we present the first investigation of the mycorrhizal associates of all species of a well-characterized orchid genus comprised exclusively of mycoheterotrophic species. With the employment of molecular phylogenetic methods, we identify the fungal associates of each of nine Hexalectris species from 134 individuals and 42 populations. We report that Hexalectris warnockii associates exclusively with members of the Thelephoraceae, H. brevicaulis and H. grandiflora associate with members of the Russulaceae and Sebacinaceae subgroup A, while each member of the H. spicata species complex associates primarily with unique sets of Sebacinaceae subgroup A clades. These results are consistent with other studies of mycorrhizal specificity within mycoheterotrophic plants in that they suggest strong selection within divergent lineages for unique associations with narrow clades of mycorrhizal fungi. Our results also suggest that mycorrhizal associations are a rapidly evolving characteristic in the H. spicata complex.     

Non-functional flowers in Cat as e turn orchids (Gatasetinae, Orchidaceae)

ROMERO, G. A., 1992. Non-functional flowers in Catasetum orchids (Catasetinae, Orchidaceae). Plants of the genus Catasetum generally produce unisexual, dimorphic flowers but occasionally bear intermediate, polymorphic flowers. Staminate (male) flowers are commonly produced both in cultivation and in nature. Within the genus, the morphology, texture, resupination, and colour of male flowers are extremely variable. Pistillate (female) flowers, in contrast, are rarely produced in cultivation and in nature and have relatively constant morphology, texture, resupination and colour. Intermediate, polymorphic flowers are extremely rare, ranging in morphology from male-like to female-like, often combining characters of both. Some are bilaterally half male and half female. Intermediate flowers have previously been regarded as functionally hermaphroditic but evidence presented here shows that in Catasetum male and female functions appear to be mutually exclusive. Intermediate flowers that approach the morphology of female flowers may bear seeds but do not have functional pollinaria; those that approach male flower morphology do not have functional stigmas and seldom have functional pollinaria. The vast majority of Catasetum intermediate flowers are sterile. The absence of truly hermaphroditic flowers in Catasetum is important in the interpretation of evidence for gender choice in this genus, as flowers and/or plants can be unequivocally scored as either functionally male or female.     

Molecular phylogenetics of Vandeae (Orchidaceae) and the evolution of leaflessness

Members of tribe Vandeae (Orchidaceae) form a large, pantropical clade of horticulturally important epiphytes. Monopodial leafless members of Vandeae have undergone extreme reduction in habit and represent a novel adaptation to the canopy environment in tropical Africa, Asia, and America. To study the evolution of monopodial leaflessness, molecular and structural evidence was used to generate phylogenetic hypotheses for Vandeae. Molecular analyses used sequence data from ITS nrDNA, trnL-F plastid DNA, and matK plastid DNA. Maximum parsimony analyses of these three DNA regions each supported two subtribes within monopodial Vandeae: Aeridinae and a combined Angraecinae + Aerangidinae. Adding structural characters to sequence data resulted in trees with more homoplasy, but gave fewer trees each with more well-supported clades than either data set alone. Two techniques for examining character evolution were compared: (1) mapping vegetative characters onto a molecular topology and (2) tracing vegetative characters onto a combined structural and molecular topology. In both cases, structural synapomorphies supporting monopodial Vandeae were nearly identical. A change in leaf morphology (usually reduced to a nonphotosynthetic scale), monopodial growth habit, and aeration complexes for gas exchange in photosynthetic roots seem to be the most important characters in making the evolutionary transition to leaflessness.     

Sibling species of fragrant orchids (Gymnadenia: Orchidaceae, Magnoliophyta) in Russia

Recent molecular phylogenetic studies of the genus Gymnadenia have demonstrated that it contains sibling taxa, i.e., species that are hardly distinguishable according to morphological traits, yet are phylogenetically rather distant and distinctly distinguishable by molecular methods, which is a rare phenomenon for angiosperms. By sequencing the ITS1-5.8S rDNA-ITS2 fragment the presence of G. densiflora was confirmed for Russia. Our data supported a high degree of genetic differentiation between G. conopsea s. str. and G. densiflora, which confirms their taxonomic rank of species. Morphological analysis has shown that the features that are best for the discrimination between these two species in Northwestern Russia are the length of the lower bract, length of the mid-lobe of the lip, and width of leaves. The ecological and phenological differentiation between G. conopsea s. str. and G. densiflora is briefly reviewed. The ITS sequence variation in these species has been analyzed; the molecular genetic differences of the G. conopsea individuals from the eastern part of the distribution area have been discovered for the first time. Different taxonomic interpretations of Gymnadenia phylogenetic tree topology taking into account the presence of sibling species are discussed in general.     

Phylogenetics of the slipper orchids (Cypripedioideae, Orchidaceae): Nuclear rDNA ITS sequences

Cypripedioideae (Orchidaceae) have been the subject of numerous taxonomic treatments with conflicting interpretations of relationships among the five genera and the 150–170 species. We have produced nuclear ribosomal ITS nucleotide sequences for nearly 100 slipper orchid species and used parsimony analysis to investigate their relationships. Our results demonstrate that each genus, as currently circumscribed, is monophyletic (Mexipedium andSelenipedium being represented by a single taxon). LikerbcL data, ITS sequences placeMexipedium sister toPhragmipedium. Relationships at the sectional level inPaphiopedilum are largely as described byCribb. However, the division ofPaphiopedilum into subgg.Brachypetalum andPaphiopedilum is not supported; subg.Brachypetalum is paraphyletic to subg.Paphiopedilum. Phragmipedium species are divided into the same three major clades as in the taxonomic scheme ofMcCook. The plicate-leaved genera,Cypripedium andSelenipedium, are successive sister groups to the rest of the subfamily, confirming generally held opinions that they display plesiomorphic characters compared to the conduplicate-leaved genera. A survey of karyotypes in the context of the ITS tree reveals a general trend toward increased chromosome number, probably brought about by centric fission. These data also accord with a previously suggested biogeographic hypothesis of a widespread Northern Hemisphere distribution, followed by range fragmentation due to Miocene cooling.     

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.     

Patterns of polyploid evolution in Greek marsh orchids (Dactylorhiza; Orchidaceae) as revealed by allozymes, AFLPs, and plastid DNA data

Polyploidy is common in higher plants, and speciation in polyploid complexes is usually the result of reticulate evolution. We examined variation in nuclear AFLP fingerprints, nuclear isozymes, and hypervariable plastid DNA loci to describe speciation patterns and species relationships in the Dactylorhiza incarnata/maculata polyploid complex (marsh orchids; Orchidaceae) in Greece. Several endemic taxa with restricted distribution have been described from this area, and to propose meaningful conservation priorities, detailed relationships need to be known. We identified four independently derived allopolyploid lineages, which is a pattern poorly correlated with prevailing taxonomy. Three lineages were composed of populations restricted to small areas and may be of recent origins from extant parental lineages. One lineage with wide distribution in northern Greece was characterized by several unique plastid haplotypes that were phylogenetically related and evidently older. The D. incarnata/maculata polyploid complex in Greece has high levels of genetic diversity at the polyploid level. This diversity has accumulated over a long time and may include genetic variants originating from now extinct parental populations. Our data also indicate that the Balkans may have constituted an important refuge from which northern European Dactylorhiza were recruited after the Weichselian ice age.     

Karyomorphology, heterochromatin patterns and evolution in the genus Ophrys (Orchidaceae)

Karyotype structures and heterochromatin distribution in representative taxa of the genus Ophrys are compared, based on Feulgen-stained and banded somatic metaphase chromosomes. The karyotypes of Ophrys iricolor , O. lupercalis , O. caesiella , O. lutea , O. lunulata , O. x. tardans , O. apifera , O. praecox , O. lacaitae and O. insectifera are described for the first time. The karyological analyses indicate the relationships among the species with respect to asymmetry indices and heterochromatin content. Chromosomal differences have been helpful in clarifying the taxonomic position of Ophrys species that do not have clear affinities. The representative species of Araniferae , Fuciflorae and Ophrys sections exhibited the most asymmetrical karyotypes, while chromosome complements of the O. fusca–O. lutea group, of O. tenthredinifera and of O. bombyliflora proved to be less asymmetrical. Weakly heterochromatic chromosomes, with heterochromatin present mostly in thin centromeric bands, characterize Ophrys C-banded karyotypes. Chromomycin A₃ (CMA) staining revealed that the analysed species exhibit a weak pattern of CMA⁺ bands at centromeric, intercalary or telomeric regions. No DAPI bright blocks were observed. The significance of the karyological data is discussed with regard to the relationships between the analysed species. © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 148 , 87–99.     

Molecular evolution of the OrcPI locus in natural populations of Mediterranean orchids

The evolutionary analysis of OrcPI, the orchid homologue to the PISTILLATA/GLOBOSA gene, was conducted on some Mediterranean orchid species, measuring mean pairwise Ka/Ks ratios and nucleotide variability. Evidence for positive selection was tested using a maximum likelihood approach implemented in PAML, and neutrality tests were conducted to assess deviation from neutral evolution. Data were also examined partitioning the coding region into four regions, corresponding to different functional domains of the protein. The results show that OrcPI is subjected to different evolutionary forces: diffuse purifying selection, localized positive selection or selective sweep, and different partitions of selective constraints.     

The consequences of rewardlessness in orchids: reward-supplementation experiments with Anacamptis morio (Orchidaceae)

Pollinators are expected to respond to low reward availability in an inflorescence by visiting fewer flowers before departure, thus potentially causing reduced visitation, but also reduced geitonogamous selfing. I tested this hypothesis using Anacamptis morio, an orchid that does not reward its pollinators. Supplementation of inflorescences with artificial nectar did not result in an increase in fruit set on supplemented inflorescences compared to control inflorescences and tended to reduce pollinia removal. Supplementation resulted in reduced fruit quality, but there was no evidence that this was as a result of inbreeding depression. Behavioral experiments showed that pollinating bumble bees, as predicted, visited more flowers on supplemented inflorescences. Bumble bees also deposited more self-pollen on supplemented inflorescences, but this was marginally significant. Bumble bee queens removed significantly more pollinia from control inflorescences, while Bombus terrestris and B. lucorum workers did not. I conclude that while pollinators behaved as predicted, there was weak evidence that pollinia removal, pollen deposition, and fruit set followed the predictions of the hypothesis. I argue that this was probably because some pollinators were more efficient at removing and depositing pollen on control inflorescences, while others were not.     

Morphological and genomic evidence for a new species of Corallorhiza (Orchidaceae: Epidendroideae) from SW China

Corallorhiza sinensis, a new species of mycoheterotrophic orchid from western Sichuan, China, is described and illustrated based on molecular and morphological evidence. It is morphologically similar to Corallorhiza trifida, but can be distinguished by bigger flowers, both sepals and petals with 3 veins, and longer lateral lobes of lip. To distinguish the new Corallorhiza species and explore its phylogenetic position within subtribe Calypsoinae, this study employed sequences of the nuclear ribosomal DNA (nrDNA) and whole plastome assembled from the genome skimming approach. The plastome is 148,124 bp in length, including a pair of inverted repeats (IRs) of 26,165 bp, a large single-copy region (LSC) of 82,207 bp, and a small single-copy region (SSC) of 13,587 bp. Further, phylogenetic analyses were performed using nrDNA sequence and 79 coding sequences (CDSs) from 26 complete plastomes of subtribe Calypsoinae. The phylogenetic tree based on nrDNA sequence suggested that Corallorhiza is a monophyletic group, and strongly support C. sinensis as sister to the rest species of Corallorhiza. The plastid tree showed that 10 Corallorhiza species grouped into two clades and C. sinensis is most closely related to the North American C. striata and C. bentleyi instead of Oreorchis foliosa and O.angustata in the same clade. The plastid tree and nrDNA tree indicate Oreorchis is a paraphyletic. Although the topological conflicts are displayed between plastome and nrDNA phylogenies of C. sinensis, it is still the most closely related to Corallorhiza. Comparative analysis showed that C. sinensis populations are characteristic of the intermediate morphological traits between Corallorhiza and Oreorchis. The finding of this new species from China shed new light on the phylogeny of Oreorchis and Corallorhiza.