Identification of high-copy number long terminal repeat retrotransposons and their expansion in Phalaenopsis orchids

BACKGROUND

Transposable elements (TEs) are fragments of DNA that can insert into new chromosomal locations. They represent a great proportion of eukaryotic genomes. The identification and characterization of TEs facilitates understanding the transpositional activity of TEs with their effects on the orchid genome structure.

RESULTS

We combined the draft whole-genome sequences of Phalaenopsis equestris with BAC end sequences, Roche 454, and Illumina/Solexa, and identified long terminal repeat (LTR) retrotransposons in these genome sequences by using LTRfinder and classified by using Gepard software. Among the 10 families Gypsy-like retrotransposons, three families Gypsy1, Gypsy2, and Gypsy3, contained the most copies among these predicted elements. In addition, six high-copy retrotransposons were identified according to their reads in the sequenced raw data. The 12-kb Orchid-rt1 contains 18,000 copies representing 220 Mbp of the P. equestris genome. Southern blot and slot blot assays showed that these four retrotransposons Gypsy1, Gypsy2, Gypsy3, and Orchid-rt1 contained high copies in the large-genome-size/large-chromosome species P. violacea and P. bellina. Both Orchid-rt1 and Gypsy1 displayed various ratios of copy number for the LTR sequences versus coding sequences among four Phalaenopsis species, including P. violacea and P. bellina and small-genome-size/small-chromosome P. equestris and P. ahprodite subsp. formosana, which suggests that Orchid-rt1 and Gypsy1 have been through various mutations and homologous recombination events. FISH results showed amplification of Orchid-rt1 in the euchromatin regions among the four Phalaenopsis species. The expression levels of Peq018599 encoding copper transporter 1 is highly upregulated with the insertion of Orchid-rt1, while it is down regulated for Peq009948 and Peq014239 encoding for a 26S proteasome non-ATP regulatory subunit 4 homolog and auxin-responsive factor AUX/IAA-related. In addition, insertion of Orchid-rt1 in these three genes are all in their intron regions.

CONCLUSION

Orchid-rt1 and Gypsy1-3 have amplified within Phalaenopsis orchids concomitant with the expanded genome sizes, and Orchid-rt1 and Gypsy1 may have gone through various mutations and homologous recombination events. Insertion of Orchid-rt1 is in the introns and affects gene expression levels.

Phylogenetic relationships amongst the African genera of subtribe Orchidinae s.l. (Orchidaceae; Orchideae): Implications for subtribal and generic delimitations

Phylogenetic relationships within the Orchideae sensu Pridgeon et al, remain one of the biggest unresolved issues in our understanding of the taxonomy of the orchids. Members of the Orchideae are numerous and widespread in Africa but remain poorly represented in phylogenetic research. In this study we included a broad sampling of African taxa for which we sequenced three plastid (rbcl, matK and trnL + trnL-F) and two nuclear regions (ITS and 18S). We used 368 sequences representing 278 species and 49 genera to infer relationships using the Bayesian Inference and Maximum Likelihood method. Our results show strong support for three clades, two of which almost entirely match the historical circumscription of Orchidinae and Habenariinae, and the third, Bartholininae, sister to the former two, includes the genera Holothrix and Bartholina. Stenoglottis should be assigned to Orchidinae and not to Habenariinae. Several genera such as Habenaria, Cynorkis and Benthamia are shown to be para- or polyphyletic: Bonatea, Centrostigma, Platycoryne and Roeperocharis are all embedded in Habenaria; Physoceras, Arnottia and part of Benthamia are embedded in Cynorkis. We propose a subdivision of Orchideae sensu lato into nine subtribes, but refrain from making generic re-arrangements until more extensive or more in-depth studies have been done.

Assessment of violet-blue color formation in Phalaenopsis orchids

BACKGROUND

Phalaenopsis represents an important cash crop worldwide. Abundant flower colors observed in Phalaenopsis orchids range from red-purple, purple, purple-violet, violet, and violet-blue. However, violet-blue orchids are less bred than are those of other colors. Anthocyanin, vacuolar pH and metal ions are three major factors influencing flower color. This study aimed to identify the factors causing the violet-blue color in Phalaenopsis flowers and to analyze whether delphinidin accumulation and blue pigmentation formation can be achieved by transient overexpression of heterologous F3'5'H in Phalaenopsis.

RESULTS

Cyanidin-based anthocyanin was highly accumulated in Phalaenopsis flowers with red-purple, purple, purple-violet, and violet to violet-blue color, but no true-blue color and no delphinidin was detected. Concomitantly, the expression of PeF3'H (Phalaenopsis equestrsis) was high, but that of PhF3'5'H (Phalaenopsis hybrid) was low or absent in various-colored Phalaenopsis flowers. Transient overexpression of DgF3'5'H (Delphinium grandiflorum) and PeMYB2 in a white Phalaenopsis cultivar resulted a 53.6% delphinidin accumulation and a novel blue color formation. In contrast, transient overexpression of both PhF3'5'H and PeMYB2 did not lead to delphinidin accumulation. Sequence analysis showed that the substrate recognition site 6 (SRS6) of PhF3'5'H was consistently different from DgF3'5'Hs at positions 5, 8 and 10. Prediction of molecular docking of the substrates showed a contrary binding direction of aromatic rings (B-ring) with the SRS6 domain of DgF3'5'H and PhF3'5'H. In addition, the pH values of violet-blue and purple Phalaenopsis flowers ranged from 5.33 to 5.54 and 4.77 to 5.04, respectively. Furthermore, the molar ratio of metal ions (including Al3+, Ca2+ and Fe3+) to anthocyanin in violet-blue color Phalaenopsis was 190-, 49-, and 51-fold higher, respectively, than those in purple-color Phalaenopsis.

CONCLUSION

Cyanidin-based anthocyanin was detected in violet-blue color Phalaenopsis and was concomitant with a high pH value and high molar ratio of Al3+, Ca2+ and Fe3+ to anthocyanin content. Enhanced expression of delphinidin is needed to produce true-blue Phalaenopsis.

Cytotoxic effect of selected wild orchids on two different human cancer cell lines

Majority of the orchid species are used in the traditional medicines for the treatment of several diseases. They are the sources of polysaccharides, phenanthrenes, bibenzyl derivatives, revesteral, stilbenoids and polyphenol compounds. This study explored the cytotoxic activity of seven wild orchid species and identification of medicinally active compounds. The extracts of orchid species were screened for cytotoxic effect on the human cervical cancer cells (HeLa) and human glioblastoma cells (U251) using an MTT assay. The medicinally active compounds of high cytotoxic extracts were identified by GC-MS resulting in many stilbenoids and phenolic derivatives. The extract of Dendrobium transparens (DTs) and Vanda cristata (VCw) showed high cytotoxic effect towards the HeLa and U251 cell lines (IC50 of DTs: 382.14 μg/ml and 75.84 μg/ml respectively and IC50 of VCw: 317.23 μg/ml and 163.66 μg/ml respectively). This study concludes that they could be used as cancer therapeutics.

Moscatilin, a bibenzyl derivative from the orchid Dendrobium loddigesii, induces apoptosis in melanoma cells

The use of orchids in herbal medicine has a very long history. Dendrobium species are known to produce a variety of secondary metabolites such as phenanthrens, bibenzyls, fluorenones and sesquiterpenes, and alkaloids and are responsible for their wide variety of medicinal properties. For decades, bibenzyls, which are the main bioactive components derived from Dendrobium species, have been subjected to extensive investigation as likely candidates for cancer treatment. The present study was undertaken to investigate the effect of moscatilin, a bibenzyl derivative from the orchid Dendrobium loddigesii on human melanoma cells. In A375 cells compound moscatilin showed a clear dose-response relationship in the range of 6.25-50 μM concentrations. In addition, we demonstrated an apoptotic response after treatment of cancer cells with this bibenzyl compound at 6.25 and 12.5 μM concentrations that probably involves PTEN activity, inhibition of Hsp70 expression and reactive oxygen species production. Alternatively, the inhibition of the caspase cascade at higher concentrations, 25 and 50 μM, correlated with additional reactive oxygen species increase, probably switched the mode of moscatilin-induced cell death from apoptosis to necrosis.

Towards a taxonomic revision of the genus Cyrtochilum (Orchidaceae) in Northwestern South America (Northern Peru, Ecuador, Colombia, Venezuela)

This article is a presentation of taxonomic diversity of the orchid genus Cyrtochilum in Northwestern South America. The morphological characteristics of over 90 species occurring in northern Peru, Ecuador, Colombia and Venezuela are presented together with illustrations of their floral segments. Information about the distribution of each taxon is provided. Ten morphologically consistent groups have been delineated to facilitate identification of Cyrtochilum representatives in the studied area. Keys for determination of species within each group are provided. Seven new species of Cyrtochilum are described and one new combination is proposed.

Heavy metal tolerance of orchid populations growing on abandoned mine tailings: A case study in Sardinia Island (Italy)

Understanding how environmental pollutants influence plant occurrence, growth, and development is key for effective management plans and potential bioremediation. Rare plants, such as orchids, may occur in modified habitats and on soils containing heavy metals, yet their ecological and physiological responses to heavy metals is poorly understood. We investigated the influence of heavy metal pollution on orchid growth rates and interactions with soil fungal mutualists by comparing a large population of the orchid Epipactis helleborine (L.) Crantz subsp. tremolsii (Pau) E. Klein that grows on mine tailings in south-west Sardinia (Italy) with a population that grows on non-contaminated soils in central Sardinia. Soils of the contaminated site had high levels of heavy metals and low organic matter and nutritive elements content. We performed a morphological analysis on twenty individuals that have been subjected to measurement of bioaccumulation and translocation of heavy metals. Fungi associated with the roots of plants from the contaminated and uncontaminated site were grown and identified by DNA barcoding approach. Plants from the contaminated site were smaller than the ones growing in the uncontaminated site and were found to be able to tolerate heavy metals from the soil and to accumulate and translocate them into their organs. Fungi belonging to the genus Ilyonectria (Ascomycota) were found both in contaminated and uncontaminated sites, while an unidentified fungus was isolated from roots in the contaminated site only. These results are discussed in terms of orchids' tolerance to heavy metals and its physiological and ecological mechanisms. The role of contaminated habitats in harbouring orchids and peculiar taxa is also discussed.

Implications of salep collection for the conservation of the Elder-flowered orchid (Dactylorhiza sambucina) in Epirus, Greece

Background

In Epirus, Greece, orchids have been traditionally harvested for the production of salep, a beverage made from their tubers. Over-collection of orchids for salep is believed to be a growing threat to wild species, yet very little research has concentrated on orchid populations in the wild. Here, we studied the impact of salep collection on population demographic parameters and uniformity of distribution patterns of the Elder-flowered orchid, Dactylorhiza sambucina, the most commonly collected orchid in northern Greece.

Methods

We carried out fieldwork in four meadows where salep harvesting occurs, and conducted interviews in villages close to these sites. Fieldwork focused on the demographic parameters of orchid populations and on the characteristics of their habitat (natural-anthropogenic). We also measured population size and distribution, extent and multi-scale density, comparing distributions to Poisson and fractal models.

Results

According to interviews, salep collection by the local community has decreased, contrary to collection by people outside the community, which is increasing. Interviewees did not believe that orchid abundance was higher in the past; they claim that it can be very variable. None of the participants seemed aware of the legislation to conserve orchids. Demographic parameters did not seem to be strongly dependent on whether it was a harvested and non-harvested sites and population density was greatest in the site of highest collection pressure.

Conclusions

Our findings show that salep collection is still ongoing in Epirus. Our interview results and our population study indicate that current levels of collection are not significantly affecting the abundance of the Elder-flowered orchid in Epirus subalpine meadows. However, the expanding commercial collection could reach levels that threaten the species. There is a need for a longer-term monitoring of these orchid populations, and a more effective modeling of the species’ response to different harvesting pressures.

Identification and expression profiling of selected MADS-box family genes in Dendrobium officinale

Dendrobium officinale, a herb with highly medicinal and ornamental value, is widely distributed in China. MADS-box genes encode transcription factors that regulate various growth and developmental processes in plants, particular in flowering. However, the MADS-box genes in D. officinale are largely unknown. In our study, expression profiling analyses of selected MADS-box genes in D. officinale were performed. In total, 16 DnMADS-box genes with full-length ORF were identified and named according to their phylogenetic relationships with model plants. The transient expression of eight selected MADS-box genes in the epidermal cells of tobacco leaves showed that these DnMADS-box proteins localized to the nucleus. Tissue-specific expression analysis pointed out eight flower-specific expressed MADS-box genes in D. officinale. Furthermore, expression patterns of DnMADS-box genes were investigated during the floral transition process. DnMADS3, DnMADS8 and DnMADS22 were significantly up-regulated in the reproductive phase compared with the vegetative phase, suggesting putative roles of these DnMADS-box genes in flowering. Our data showed that the expressions of MADS-box genes in D. officinale were controlled by diverse exogenous phytohormones. Together, these findings will facilitate further studies of MADS-box genes in Orchids and broaden our understanding of the genetics of flowering.

Aroma components of Cephalanthera orchids

The SPME-GC-MS analysis of the aroma components of Cephalanthera damasonium, Cephalanthera rubra, and Cephalanthera longifolia were reported. The main components found in C. damasonium were pentadecane, hexadecane, heptadecane and α-farnesene. The same compounds were found in the scent of C. rubra. Although C. damasonium and C. rubra have different pollination mechanisms, their spectrum of volatile compounds surprisingly does not differ significantly. In C. longifolia pentadecane and heptadecane were found together with cis-β-farnesene. As C. longifolia is allogamous, the differences in scent composition may play a role in pollinator attraction.

Gamma irradiation induced effects on in vitro shoot cultures and influence of monochromatic light regimes on irradiated shoot cultures of Dendrobium sonia orchid

•

Monochromatic light source affected growth of gamma irradiated in vitro cultures of Dendrobium

•

Yellow and red monochromatic lights significantly improved survival rate and growth of irradiated cultures.

•

Intra-somatic competition among mutated and non-mutated cultures can be managed by monochromatic light through better growth in vitro.

The effects of gamma radiation and monochromatic lights on growth of in vitro shoot cultures of orchid, Dendrobium sonia, were investigated. The gamma irradiated shoot cultures grown under white, blue, yellow and red monochromatic lights exhibited differential growth pattern. Shoot cultures gamma irradiated at 15–45 Gy showed reduced shoot length, fresh weight and leaf area. The monochromatic light significantly influenced survival rate and growth of irradiated shoots. The yellow and red light treatments positively influenced survival of gamma irradiated shoots with significant increase in fresh weight, shoot length and chlorophyll content. Yellow light was found to be most effective as leaf area was increased across the radiation dose range (15–100 Gy) compared to red light. The results demonstrated that the method of post-irradiation exposure could be useful to improve growth of gamma irradiated in vitro shoots, and help to recover orchid mutants with novel modifications.

Effect of Coelogyne cristata Lindley in alleviation of chronic fatigue syndrome in aged Wistar rats

BACKGROUND

Swarna Jibanti scientifically known as Coelogyne cristata Lindley (Orchidaceae), an orchid mentioned in Ayurvedic medicine is used to promote healthy life span.

OBJECTIVE(S)

The present work was planned to study the efficacy of hydro-alcoholic extract of pseudobulbs of C. cristata (CCE) to assess its role on chronic fatigue syndrome (CFS) induced behavioural and biochemical changes in aged Wistar rats compared to Panax ginseng (PG), a prototype anti-stress agent.

MATERIALS AND METHODS

CFS was induced by forced swimming for consecutive 21 days for fixed duration (15 min sessions). The criteria of CFS due to fatigue were counted using locomotor activity, depression and anxiety through automated photactometer, immobility time and plus maze activity respectively. Acute toxicity study of CCE (upto 2 g/kg, Limit test) was also performed. For CFS, animals were divided into five groups, naive control, control, CCE treated (25 mg/kg b.w., 250 mg/kg b.w.) and standard PG treated (100 mg/kg b.w.) groups. All drugs were given orally for consecutive 21 days along with CFS. After assessing behavioural parameters, all animals were sacrificed at day 21 and in vivo antioxidant potential of CCE was determined by lipid peroxides, nitrite, catalase (CAT) and superoxide dismutase (SOD) in brain tissue.

RESULTS

CCE was found to be non-toxic. CCE treated aged rats significantly improved (p < 0.001) the spontaneous locomotor movement with respect to control rats, while, decreased the mobility period or depression score. In CFS, CCE also enhanced the time spent (p < 0.001) in open arms while reducing the time spent in closed arm as compared to CFS control, indicating lowering anxiety score. Moreover, marked diminution in lipid peroxidation, nitrite and SOD level was exhibited after CCE treatment and significantly enhanced catalase level significantly (p < 0.01) with respect to CFS control. PG also showed similar actions.

CONCLUSION

The results confirmed the potential therapeutic actions of CCE against experimentally induced CFS in aged rats that might be due to its CNS mediatory antioxidant properties.

The use of chloroplast genome sequences to solve phylogenetic incongruences in Polystachya Hook (Orchidaceae Juss)

BACKGROUND

Current evidence suggests that for more robust estimates of species tree and divergence times, several unlinked genes are required. However, most phylogenetic trees for non-model organisms are based on single sequences or just a few regions, using traditional sequencing methods. Techniques for massive parallel sequencing or next generation sequencing (NGS) are an alternative to traditional methods that allow access to hundreds of DNA regions. Here we use this approach to resolve the phylogenetic incongruence found in Polystachya Hook. (Orchidaceae), a genus that stands out due to several interesting aspects, including cytological (polyploid and diploid species), evolutionary (reticulate evolution) and biogeographical (species widely distributed in the tropics and high endemism in Brazil). The genus has a notoriously complicated taxonomy, with several sections that are widely used but probably not monophyletic.

METHODS

We generated the complete plastid genome of 40 individuals from one clade within the genus. The method consisted in construction of genomic libraries, hybridization to RNA probes designed from available sequences of a related species, and subsequent sequencing of the product. We also tested how well a smaller sample of the plastid genome would perform in phylogenetic inference in two ways: by duplicating a fast region and analyzing multiple copies of this dataset, and by sampling without replacement from all non-coding regions in our alignment. We further examined the phylogenetic implications of non-coding sequences that appear to have undergone hairpin inversions (reverse complemented sequences associated with small loops).

RESULTS

We retrieved 131,214 bp, including coding and non-coding regions of the plastid genome. The phylogeny was able to fully resolve the relationships among all species in the targeted clade with high support values. The first divergent species are represented by African accessions and the most recent ones are among Neotropical species.

DISCUSSION

Our results indicate that using the entire plastid genome is a better option than screening highly variable markers, especially when the expected tree is likely to contain many short branches. The phylogeny inferred is consistent with the proposed origin of the genus, showing a probable origin in Africa, with later dispersal into the Neotropics, as evidenced by a clade containing all Neotropical individuals. The multiple positions of Polystachya concreta (Jacq.) Garay & Sweet in the phylogeny are explained by allotetraploidy. Polystachya estrellensis Rchb.f. can be considered a genetically distinct species from P. concreta and P. foliosa (Lindl.) Rchb.f., but the delimitation of P. concreta remains uncertain. Our study shows that NGS provides a powerful tool for inferring relationships at low taxonomic levels, even in taxonomically challenging groups with short branches and intricate morphology.

External and local controls on land-sea coupling assessed by stable isotopic signatures of mangrove producers in estuaries of Pacific Panama

Foliar stable isotopic signatures of nitrogen, carbon, and sulfur in mangrove vegetation from the Pacific coast of Panama were insensitive to inputs from watersheds with different area of forest land cover, and to seasonal, inter-annual, and global-scale-driven contrasts in rainfall and upwelling. N, C, and S content of mangrove vegetation were not affected by inputs from watersheds with different degrees of deforestation, but showed some influence of down-estuary transformations. While there was substantial variation that remained un-explained, isotopic signatures and nutrient contents were largely determined by species-specific features, and showed substantial small-scale variation reflecting local differences, within-estuary plant-sediment links. The ability of mangrove estuaries to erase effects of deforestation points out that conservation of these wetland ecosystems is important, because, at least in the sites we studied, transformations within mangrove estuaries were strong enough to protect water quality in receiving coastal waters.

Differences among Endophytic Fungal Communities Isolated from the Roots of Cephalanthera longibracteata Collected from Different Sites in Korea

Orchidaceous plants have symbiotic relationships with endophytic fungi, including mycorrhizal fungi, which play important roles in the seed germination and growth of the host plants. In this study, endophytic fungal communities isolated from the roots of Cephalanthera longibracteata collected from three different sites in Korea were analyzed, and it was determined whether fungal communities were preferentially correlated with the sites. The fungal isolates were identified by sequence analysis of the internal transcribed spacer regions of rDNA. In total, 30 species of endophytic fungi, including two species of mycorrhizal fungi belonging to the genus Tulasnella, were identified. Leptodontidium orchidicola showed the highest frequency and was isolated from all root samples. Species diversity and richness were not significantly different among sites. However, the community structure of the endophytic fungi significantly differed among sites, suggesting that the site characteristics affected the community composition of the endophytic fungi colonizing the roots of C. longibracteata. Our findings will aid in developing methods involving the use of symbiotic fungi for orchid conservation and restoration in native habitats.

Bioactive Secondary Metabolites from Orchids (Orchidaceae)

The Orchidaceae family is the largest group of flowering plants in the Angiosperm monocotyledons spread on our planet. Its members, called orchids, are herbs or epiphytes with showy flowers distributed mainly in tropical regions. Several classes of phytoconstituents have been so far isolated from therapeutically-used orchids showing a great chemical diversity. Among them, phenolic derivatives have been studied for their biological activities, especially in the field of cancer, inflammation, and neurodegeneration. On the other hand, limited information has been so far obtained on the numerous alkaloids and terpenoids isolated from several orchid species. Recent articles revealed pronounced effects of some alkaloids on the CNS. Published literature on orchids that are used in traditional medicine has been reviewed in this work indicating a great potential of such organisms as source of chemical entities for the development of new drugs.

De novo transcriptome analysis in Dendrobium and identification of critical genes associated with flowering

Artificial control of flowering time is pivotal for the ornamental value of orchids including the genus Dendrobium. Although various flowering pathways have been revealed in model plants, little information is available on the genetic regualtion of flowering in Dendrobium. To identify the critical genes associated with flowering, transcriptomes from four organs (leaf, root, stem and flower) of D. officinale were analyzed in our study. In total, 2645 flower-specific transcripts were identified. Functional annotation and classification suggested that several metabolic pathways, including four sugar-related pathways and two fatty acid-related pathways, were enriched. A total of 24 flowering-related transcripts were identified in D. officinale according to the similarities to their homologous genes from Arabidopsis, suggesting that most classical flowering pathways existed in D. officinale. Furthermore, phylogenetic analysis suggested that the FLOWERING LOCUS T homologs in orchids are highly conserved during evolution process. In addition, expression changes in nine randomly-selected critical flowering-related transcripts between the vegetative stage and reproductive stage were quantified by qRT-PCR analysis. Our study provided a number of candidate genes and sequence resources for investigating the mechanisms underlying the flowering process of the Dendrobium genus.

An annotated translation of Noël Bernard's 1899 article 'On the germination of Neottia nidus-avis'

We translate Noël Bernard's discovery of orchid symbiotic germination discovered on Neottia nidus-avis, as published in the May 1899 issue of the Comptes rendus hebdomadaires des séances de l'Académie des sciences. In his note, Bernard (1874-1911) establishes the need for a fungus, which is also forming mycorrhizae in adults, for seeds germination. We provide illustrations reproduced from his later works, and summaries of the French text he cited. In our annotations, we show how early this discovery was done in Bernard's career, and insist on the scientific framework at the end of the nineteenth century, where orchid germination was mysterious and the need for vicinity of parents was not fully understood. We comment the text of Bernard on the basis of the most recent knowledge on Neottia nidus-avis and on orchid mycorrhizal fungi. Introducing his following papers, we finally discuss the emergence of the concept of peloton digestion, and how Bernard's work quickly paved the way to a general understanding of mycoheterotrophic germination in orchids and beyond.

Leaf arrangements are invalid in the taxonomy of orchid species

The selection and validation of proper distinguishing characters are of crucial importance in taxonomic revisions. The modern classifications of orchids utilize the molecular tools, but still the selection and identification of the material used in these studies is for the most part related to general species morphology. One of the vegetative characters quoted in orchid manuals is leaf arrangement. However, phyllotactic diversity and ontogenetic changeability have not been analysed in detail in reference to particular taxonomic groups. Therefore, we evaluated the usefulness of leaf arrangements in the taxonomy of the genus Epipactis Zinn, 1757. Typical leaf arrangements in shoots of this genus are described as distichous or spiral. However, in the course of field research and screening of herbarium materials, we indisputably disproved the presence of distichous phyllotaxis in the species Epipactis purpurata Sm. and confirmed the spiral Fibonacci pattern as the dominant leaf arrangement. In addition, detailed analyses revealed the presence of atypical decussate phyllotaxis in this species, as well as demonstrated the ontogenetic formation of pseudowhorls. These findings confirm ontogenetic variability and plasticity in E. purpurata. Our results are discussed in the context of their significance in delimitations of complex taxa within the genus Epipactis.

Sympatric reinforcement of reproductive barriers between Neotinea tridentata and N. ustulata (Orchidaceae)

Reinforcement is the process by which selection favors traits that decrease mating between two incipient species in response to costly mating or the production of maladapted hybrids, causing the evolution of greater reproductive isolation between emerging species. I have studied a pair of orchids, Neotinea tridentata and N. ustulata, to examine the level of postmating pre- and post-zygotic isolating mechanisms that maintain these species, and the degree to which the boundary may still be permeable to gene flow. In this study, I performed pollen tube growth rate experiments and I investigated pre- and post-zygotic barriers by performing hand pollination experiments in order to evaluate fruit set, embryonate seed set and seed germination rates by intra- and interspecific crosses. Fruit set, the percentage of embryonate seeds and germinability of interspecific crosses were reduced compared to intraspecific pollinations, showing significant differences between sympatric and allopatric populations. While in allopatric populations the post-pollination isolation index ranged between 0.40 and 0.11, in sympatric populations orchid pairs showed total isolation due to post-pollination prezygotic barriers, guaranteed at the level of pollen-stigma interactions. Indeed, in sympatric populations, pollen tubes reached the ovary after 24 h in only 8 out of 45 plants; in the remaining cases, the pollen tubes did not enter the ovary, and thus no fruit set occurred. This pair of orchids is characterized by postmating pre-zygotic reproductive isolation in sympatric populations that prevents the formation of hybrids. This mechanism of speciation, starting in allopatry and triggering the reinforcement mechanisms of reproductive isolation in secondary sympatry, is the most likely explanation for the pattern of evolutionary transitions found in this pair of orchids.

Plant species with extremely small populations (PSESP) in China: A seed and spore biology perspective

Approximately one fifth of the world's plants are at risk of extinction. Of these, a significant number exist as populations of few individuals, with limited distribution ranges and under enormous pressure due to habitat destruction. In China, these most-at-risk species are described as 'plant species with extremely small populations' (PSESP). Implementing conservation action for such listed species is urgent. Storing seeds is one of the main means of ex situ conservation for flowering plants. Spore storage could provide a simple and economical method for fern ex situ conservation. Seed and spore germination in nature is a critical step in species regeneration and thus in situ conservation. But what is known about the seed and spore biology (storage and germination) of at-risk species? We have used China's PSESP (the first group listing) as a case study to understand the gaps in knowledge on propagule biology of threatened plant species. We found that whilst germination information is available for 28 species (23% of PSESP), storage characteristics are only known for 8% of PSESP (10 species). Moreover, we estimate that 60% of the listed species may require cryopreservation for long-term storage. We conclude that comparative biology studies are urgently needed on the world's most threatened taxa so that conservation action can progress beyond species listing.

Evolution of the climatic tolerance and postglacial range changes of the most primitive orchids (Apostasioideae) within Sundaland, Wallacea and Sahul

The location of possible glacial refugia of six Apostasioideae representatives is estimated based on ecological niche modeling analysis. The distribution of their suitable niches during the last glacial maximum (LGM) is compared with their current potential and documented geographical ranges. The climatic factors limiting the studied species occurrences are evaluated and the niche overlap between the studied orchids is assessed and discussed. The predicted niche occupancy profiles and reconstruction of ancestral climatic tolerances suggest high level of phylogenetic niche conservatism within Apostasioideae.

Shapes of leaves with parallel venation. Modelling of the Epipactis sp. (Orchidaceae) leaves with the help of a system of coupled elastic beams

Static properties of leaves with parallel venation, with particular emphasis on the genus EpipactisZinn, 1757 (Orchidaceae, Neottieae) have been modelled with coupled quasi-parallel elastic “beams.” The non-linear theory of strongly bended beams have been employed. The resulting boundary-value problem has been solved numerically with the help of the finite-difference method. Possible dislocations resulting in additional Dirac-delta like forces have been take into account. Morphological similarity of the model and real leaves has been obtained. In particular, the concentrated forces have been shown to cause undulation in the leaves.

Darwin at Orchis Bank: Selection after the Origin

Darwin's first publication after the Origin of Species was a volume on orchids that expanded on the theory of adaptation through natural selection introduced in his opus. Here I argue that On the Various Contrivances by which British and Foreign Orchids are Fertilised by Insects (1862) is not merely an empirical confirmation of his theory. In response to immediate criticisms of his metaphor of natural selection, Darwin uses Orchids to present adaptation as the result of innumerable natural laws, rather than discrete acts analogous to conscious choices. The means of selection among polliniferous plants cannot be neatly classed under the Origin's categories of artificial, natural, or sexual selection. Along with Darwin's exploration of sexual selection in his later works, Orchids serves to undo the restrictive metaphor so firmly established by the Origin and to win over those of Darwin's contemporaries who were committed advocates of natural law but suspicious of evolution by natural selection.

Dendrochilum hampelii (Coelogyninae, Epidendroideae, Orchidaceae) traded as 'Big Pink' is a new species, not a hybrid: evidence from nrITS, matK and ycf1 sequence data

In 2013, an unidentified species of Dendrochilum appeared in cultivation under the commercial trade name 'Big Pink'. Using sequences of the nuclear ribosomal ITS1-5.8S-ITS2 region and of the plastid matK and ycf1 genes, we examined the phylogenetic relationships between 'Big Pink' and six other species of the phenetically defined Dendrochilum subgen. Platyclinis sect. Eurybrachium. Separate and combined analyses (using Bayesian, Maximum Likelihood and Parsimony inference) showed consistent placement of the unidentified species within a statistically well supported clade. Furthermore, the multi-copy nrITS marker showed clear distinct peaks. Thus, we found no evidence that 'Big Pink' could be a hybrid. Against this background, and further supported by species-specific mutations in (at least) nrITS and ycf1, we formally describe 'Big Pink' as a new species under the name Dendrochilum hampelii. Morphologically, it is most similar to Dendrochilum propinquum, but it differs in a number of characters. Of the two cultivated individuals available for our study, one was of unrecorded provenance. The other allegedly originated from the Philippines. Observations of the species occurring in the wild in the Philippines in the northern provinces of Bukidnon and Misamis Oriental on the island of Mindanao confirmed this.