Leafless Orchid Research Articles

Plastid genome evolution in leafless members of the orchid subfamily Orchidoideae, with a focus on Degranvillea dermaptera.

Leafless, heterotrophic plants are prime examples of organismal modification, the genomic consequences of which have received considerable interest. In particular, plastid genomes (plastomes) are being sequenced at a high rate, allowing continual refinement of conceptual models of reductive evolution in heterotrophs. However, numerous sampling gaps exist, hindering the ability to conduct comprehensive phylogenomic analyses in these plants. Using floral tissue from an herbarium specimen, we sequenced and analyzed the plastome of Degranvillea dermaptera, a rarely collected, leafless orchid species from South America about which little is known, including its phylogenetic affinities. The plastome is the most reduced of those sequenced among the orchid subfamily Orchidoideae. In Degranvillea, it has lost the majority of genes found in leafy autotrophic species, is structurally rearranged, and has similar gene content to the most reduced plastomes among the orchids. We found strong evidence for the placement of Degranvillea within the subtribe Spiranthinae using models that explicitly account for heterotachy, or lineage-specific evolutionary rate variation over time. We further found evidence of relaxed selection on several genes and of correlations among substitution rates and several other "traits" of the plastome among leafless members of orchid subfamily Orchidoideae. Our findings advance knowledge on the phylogenetic relationships and paths of plastid genome evolution among the orchids, which have experienced more independent transitions to heterotrophy than any other plant family. This study demonstrates the importance of herbarium collections in comparative genomics of poorly known species of conservation concern.

The Complete Chloroplast Genome of an Epiphytic Leafless Orchid, Taeniophyllum complanatum: Comparative Analysis and Phylogenetic Relationships

Taeniophyllum is a distinct taxon of epiphytic leafless plants in the subtribe Aeridinae of Orchidaceae. The differences in chloroplast genomes between extremely degraded epiphytic leafless orchids and other leafy orchids, as well as their origins and evolution, raise intriguing questions. Therefore, we report the chloroplast genome sequence of Taeniophyllum complanatum, including an extensive comparative analysis with other types of leafless orchids. The chloroplast genome of T. complanatum exhibited a typical quadripartite structure, and its overall structure and gene content were relatively conserved. The entire chloroplast genome was 141,174 bp in length, making it the smallest known chloroplast genome of leafless epiphytic orchids. It encoded a total of 120 genes, including repetitive genes, comprising 74 protein-coding genes, 38 transfer RNA (tRNA) genes, and 8 ribosomal RNA (rRNA) genes. A phylogenetic analysis was conducted on the chloroplast genomes of 43 species belonging to five subfamilies of Orchidaceae. The results showed that the five subfamilies were monophyly, with nearly all segments having a 100% bootstrap value. T. complanatum and Chiloschista were clustered together as a sister group to Phalaenopsis and occupied the highest position in the Epidendroideae. Phylogenetic analysis suggested that T. complanatum and other leafless orchids within the Orchidaceae evolved independently. This study may provide the foundation for research on phylogenetic and structural diversity in leafless epiphytic orchids, thereby enhancing the resources available for chloroplast genome studies in Orchidaceae.

Partial mycoheterotrophy in the leafless orchid Eulophia zollingeri specialized on wood-decaying fungi.

Although the absence of normal leaves is often considered a sign of full heterotrophy, some plants remain at least partially autotrophic despite their leafless habit. Leafless orchids with green stems and capsules probably represent a late evolutionary stage toward full mycoheterotrophy and serve as valuable models for understanding the pathways leading to this nutritional strategy. In this study, based on molecular barcoding and isotopic analysis, we explored the physiological ecology of the leafless orchid Eulophia zollingeri, which displays green coloration, particularly during its fruiting phase. Although previous studies hadshown thatE. zollingeri, in its adult stage, is associated with Psathyrellaceae fungi and exhibits high 13C isotope signatures similar to fully mycoheterotrophic orchids, it remained uncertain whether this symbiotic relationship is consistent throughout the orchid's entire life cycle and whether the orchid relies exclusively on mycoheterotrophy for its nutrition during the fruiting season. Our study has demonstratedthat E. zollingeri maintains a specialized symbiotic relationship with Psathyrellaceae fungi throughout all life stages. However, isotopic analysis and chlorophyll data have shown that the orchid also engages in photosynthesis to meet its carbon needs, particularly during the fruiting stage. This research constitutes the first discovery of partial mycoheterotrophy in leafless orchids associated with saprotrophic non-rhizoctonia fungi.

Complete genome sequence of new Microbacterium sp. strain ET2, isolated from roots of leafless orchid.

Whole-genome sequence of ET2 strain, isolated from the roots of leafless orchid, constitutes a single circular chromosome of 3,604,840 bp (69.44% G + C content). BLAST+-based average nucleotide identity (ANIb) and digital DNA-DNA hybridization values indicate that ET2 may be a novel Microbacterium species. Genes putatively involved in plant-microbial interactions were predicted.

Comparative and phylogenetic analysis of Chiloschista (Orchidaceae) species and DNA barcoding investigation based on plastid genomes

BackgroundChiloschista (Orchidaceae, Aeridinae) is an epiphytic leafless orchid that is mainly distributed in tropical or subtropical forest canopies. This rare and threatened orchid lacks molecular resources for phylogenetic and barcoding analysis. Therefore, we sequenced and assembled seven complete plastomes of Chiloschista to analyse the plastome characteristics and phylogenetic relationships and conduct a barcoding investigation.ResultsWe are the first to publish seven Chiloschista plastomes, which possessed the typical quadripartite structure and ranged from 143,233 bp to 145,463 bp in size. The plastomes all contained 120 genes, consisting of 74 protein-coding genes, 38 tRNA genes and eight rRNA genes. The ndh genes were pseudogenes or lost in the genus, and the genes petG and psbF were under positive selection. The seven Chiloschista plastomes displayed stable plastome structures with no large inversions or rearrangements. A total of 14 small inversions (SIs) were identified in the seven Chiloschista plastomes but were all similar within the genus. Six noncoding mutational hotspots (trnNGUU–rpl32 > rpoB–trnCGCA > psbK–psbI > psaC–rps15 > trnEUUC–trnTGGU > accD–psaI) and five coding sequences (ycf1 > rps15 > matK > psbK > ccsA) were selected as potential barcodes based on nucleotide diversity and species discrimination analysis, which suggested that the potential barcode ycf1 was most suitable for species discrimination. A total of 47–56 SSRs and 11–14 long repeats (> 20 bp) were identified in Chiloschista plastomes, and they were mostly located in the large single copy intergenic region. Phylogenetic analysis indicated that Chiloschista was monophyletic. It was clustered with Phalaenopsis and formed the basic clade of the subtribe Aeridinae with a moderate support value. The results also showed that seven Chiloschista species were divided into three major clades with full support.ConclusionThis study was the first to analyse the plastome characteristics of the genus Chiloschista in Orchidaceae, and the results showed that Chiloschista plastomes have conserved plastome structures. Based on the plastome hotspots of nucleotide diversity, several genes and noncoding regions are suitable for phylogenetic and population studies. Chiloschista may provide an ideal system to investigate the dynamics of plastome evolution and DNA barcoding investigation for orchid studies.

Future distribution of the epiphytic leafless orchid (Dendrophylax lindenii), its pollinators and phorophytes evaluated using niche modelling and three different climate change projections

The identification of future refugia for endangered species from the effects of global warming is crucial for improving their conservation. Because climate-driven shifts in ranges and local extinctions can result in a spatial mismatch with their symbiotic organisms, however, it is important to incorporate in niche modelling the ecological partners of the species studied. The aim of this study was to evaluate the effect of climate change on the distribution of suitable niches for the ghost orchid (Dendrophylax lindenii) and its phorophytes and pollinators. Thus, its five species of host trees and three pollen vectors were included in the analysis. Climatic preferences of all the species studied were evaluated. The modelling was based on three different climate change projections and four Shared Socio-economic Pathway trajectories. All the species analysed are characterized by narrow temperature tolerances, which with global warming are likely to result in local extinctions and range shifts. D. lindenii is likely to be subjected to a significant loss of suitable niches, but within a reduced geographical range, both host trees and pollen vectors will be available in the future. Future conservation of this orchid should focus on areas that are likely be suitable for it and its ecological partners.

Whole genome sequencing and analysis of Armillaria gallica Jzi34 symbiotic with Gastrodia elata

BackgroundArmillaria species are plant pathogens, but a few Armillaria species can establish a symbiotic relationship with Gastrodia elata, a rootless and leafless orchid, that is used as a Chinese herbal medicine. Armillaria is a nutrient source for the growth of G. elata. However, there are few reports on the molecular mechanism of symbiosis between Armillaria species and G. elata. The genome sequencing and analysis of Armillaria symbiotic with G. elata would provide genomic information for further studying the molecular mechanism of symbiosis.ResultsThe de novo genome assembly was performed with the PacBio Sequel platform and Illumina NovaSeq PE150 for the A. gallica Jzi34 strain, which was symbiotic with G. elata. Its genome assembly contained ~ 79.9 Mbp and consisted of 60 contigs with an N50 of 2,535,910 bp. There were only 4.1% repetitive sequences in the genome assembly. Functional annotation analysis revealed a total of 16,280 protein coding genes. Compared with the other five genomes of Armillaria, the carbohydrate enzyme gene family of the genome was significantly contracted, while it had the largest set of glycosyl transferase (GT) genes. It also had an expansion of auxiliary activity enzymes AA3-2 gene subfamily and cytochrome P450 genes. The synteny analysis result of P450 genes reveals that the evolutionary relationship of P450 proteins between A. gallica Jzi34 and other four Armillaria was complex.ConclusionsThese characteristics may be beneficial for establishing a symbiotic relationship with G. elata. These results explore the characteristics of A. gallica Jzi34 from a genomic perspective and provide an important genomic resource for further detailed study of Armillaria. This will help to further study the symbiotic mechanism between A. gallica and G. elata.

Cyanobacterial Root Associations of Leafless Epiphytic Orchids.

The leafless orchids are rare epiphytic plants with extremely reduced leaves, and their aerial roots adopted for photosynthesis. The beneficial plant–microbial interactions contribute significantly to host nutrition, fitness, and growth. However, there are no data available on the bacterial associations, inhabiting leafless orchids. Here, we describe the diversity of cyanobacteria, which colonize the roots of greenhouse Microcoelia moreauae and Chiloschista parishii. The biodiversity and structure of the cyanobacterial community were analyzed using a complex approach, comprising traditional cultivable techniques, denaturing gradient gel electrophoresis (DGGE), and phylogenetic analysis, as well as the light and scanning electron microscopy (SEM). A wide diversity of associated bacteria colonize the root surface, forming massive biofilms on the aerial roots. The dominant populations of filamentous nitrogen-fixing cyanobacteria belonged to the orders Oscillatoriales, Synechococcales, and Nostocales. The composition of the cyanobacterial community varied, depending on the nitrogen supply. Two major groups prevailed under nitrogen-limiting conditions, belonging to Leptolyngbya sp. and Komarekiella sp. The latter was characterized by DGGE profiling and sequencing, as well as by its distinctive features of morphological plasticity. The leading role of these phototrophophic and diazotrophic cyanobacteria is discussed in terms of the epiphytic lifestyle of the leafless orchids.

Structure and functional anatomy of the gas exchange apparatus of leafless orchids: evidence for a control mechanism?

AbstractIt is assumed that special structures in aerial roots of leafless orchids, aeration units, are involved in gas exchange regulation. In this study, the structure of aeration units in three leafless taxa (Microcoelia exilis, M. aphylla, Dendrophylax funalis) and a leaf-bearing species (Campylocentrum micranthum) are investigated to obtain more evidence of a possible mechanism for gas exchange control in aerial orchid roots. Extensive analyses of the anatomy of the velamen radicum, exodermis and cortex were performed using light and electron microscopy and µCT. In all considered leafless taxa, the aeration unit consists of pneumathodes (non-wettable regions in the velamen radicum), an exodermal aeration cell (EAC) with a thin cell wall (often equipped with a special internal layer showing a fluffy structure) and specialized cortical cells (SCC). The SCC provide gaps for gas exchange, show differentially thickened cell walls and are arranged in a staggered manner. Based on the 3D structure of the aeration unit, we suggest the possibility of dehydration-triggered gap closure (driven by root shrinkage), in the process of which first the SCC are pushed against each other and second the EAC are squeezed shut by the exodermis.

The Leafless Orchid Cymbidium macrorhizon Performs Photosynthesis in the Pericarp during the Fruiting Season.

Photosynthesis with highly photoreactive chlorophyll (Chl) provides energy for plant growth but with simultaneous risk of photooxidative damage and photoprotection costs. Although the leafless orchid Cymbidium macrorhizon mostly depends on mycorrhizal fungi for carbon, it accumulates Chl particularly during fruiting and may not be fully mycoheterotrophic. In fact, stable isotopic analysis suggested that the fruiting C. macrorhizon specimens obtain a significant proportion of its carbon demands through photosynthesis. However, actual photosynthetic characteristics of this leafless orchid are unknown. To reveal the functionality of photosynthetic electron transport in C. macrorhizon, we compared its photosynthetic properties with those of its relative mixotrophic orchid Cymbidium goeringii and the model plant Arabidopsis thaliana. Compared with C. goeringii and A. thaliana, maximum photochemical efficiency of PSII was substantially low in C. macrorhizon. Chl fluorescence induction kinetics revealed that the electron transport capacity of PSII was limited in C. macrorhizon. Chl fluorescence analysis at 77 K suggested partial energetic disconnection of the light-harvesting antenna from the PSII reaction center in C. macrorhizon. Despite its low PSII photochemical efficiency, C. macrorhizon showed photosynthetic electron transport activity both in the field and under laboratory conditions. Cymbidium macrorhizon developed strong nonphotochemical quenching in response to increased light intensity as did C. goeringii, suggesting the functionality of photoprotective systems in this orchid. Moreover, C. macrorhizon fruit developed stomata on the pericarp and showed net O2-evolving activity. Our data demonstrate that C. macrorhizon can perform photosynthetic electron transport in the pericarp, although its contribution to net carbon acquisition may be limited.

Draft genomic sequence of Armillaria gallica 012m: insights into its symbiotic relationship with Gastrodia elata.

Armillaria species (Basidiomycota, Physalacriaceae) are well known as plant pathogens related to serious root rot disease on various trees in forests and plantations. Interestingly, some Armillaria species are essential symbionts of the rare Chinese medicinal herb Gastrodia elata, a rootless and leafless orchid used for over 2000years. In this work, an 87.3-M draft genome of Armillaria gallica 012m strain, which was symbiotic with G. elata, was assembled. The genome includes approximately 23.6% repetitive sequences and encodes 26,261 predicted genes. In comparison with other four genomes of Armillaria, the following gene families related to pathogenicity/saprophytic phase, including cytochrome P450 monooxygenases, carbohydrate-active enzyme AA3, and hydrophobins, were significantly contracted in A. gallica 012m. These characteristics may be beneficial for G. elata to get less injuries. The genome-guided analysis of differential expression between rhizomorph (RH) and vegetative mycelium (VM) showed that a total of 2549 genes were differentially expressed, including 632 downregulated genes and 1917 upregulated genes. In the RH, most differentially expressed genes (DEGs) related to pathogenicity were significantly upregulated. To further elucidate gene function, Gene Ontology enrichment analysis showed that the upregulated DEGs significantly grouped into monooxygenase activity, hydrolase activity, glucosidase activity, extracellular region, fungal cell wall, response to xenobiotic stimulus, response to toxic substance, etc. These phenomena indicate that RH had better infection ability than VM. The infection ability of RH may be beneficial for G. elata to obtain nutrition, because the rhizomorph constantly infected the nutritional stems of G. elata and formed the hyphae that can be digested by G. elata. These results clarified the characteristics of A. gallica 012m and the reason why the strain 012m can establish a symbiotic relationship with G. elata in some extent from the perspective of genomics.

Unprecedented Parallel Photosynthetic Losses in a Heterotrophic Orchid Genus.

Heterotrophic plants are evolutionary experiments in genomic, morphological, and physiological change. Yet, genomic sampling gaps exist among independently derived heterotrophic lineages, leaving unanswered questions about the process of genome modification. Here, we have sequenced complete plastid genomes for all species of the leafless orchid genus Hexalectris, including multiple individuals for most, and leafy relatives Basiphyllaea and Bletia. Our objectives are to determine the number of independent losses of photosynthesis and to test hypotheses on the process of genome degradation as a result of relaxed selection. We demonstrate four to five independent losses of photosynthesis in Hexalectris based on degradation of the photosynthetic apparatus, with all but two species displaying evidence of losses, and variation in gene loss extending below the species level. Degradation in the atp complex is advanced in Hexalectris warnockii, whereas only minimal degradation (i.e., physical loss) has occurred among some “housekeeping” genes. We find genomic rearrangements, shifts in Inverted Repeat boundaries including complete loss in one accession of H. arizonica, and correlations among substitutional and genomic attributes. Our unprecedented finding of multiple, independent transitions to a fully mycoheterotrophic lifestyle in a single genus reveals that the number of such transitions among land plants is likely underestimated. This study underscores the importance of dense taxon sampling, which is highly informative for advancing models of genome evolution in heterotrophs. Mycoheterotrophs such as Hexalectris provide forward-genetic opportunities to study the consequences of radical genome evolution beyond what is possible with mutational studies in model organisms alone.

Partial mycoheterotrophy in the leafless orchid Cymbidium macrorhizon

The evolution of full mycoheterotrophy is one of the most interesting topics within plant evolution. The leafless orchid Cymbidium macrorhizon is often assumed to be fully mycoheterotrophic even though it has a green stem and fruit capsule. Here, we assessed the trophic status of this species by analyzing the chlorophyll content and the natural 13 C and 15 N abundance in the sprouting and the fruiting season. The chlorophyll content was measured in five sprouting and five fruiting individuals of C. macrorhizon that were co-occurring. In addition, their 13 C and 15 N isotopic signatures were compared with those of neighboring autotrophic and partially mycoheterotrophic reference plants. Fruiting individuals of C. macrorhizon were found to contain a remarkable amount of chlorophyll compared to their sprouting counterparts. In addition, the natural abundance of 13 C in the tissues of the fruiting plants was slightly depleted relative to the sprouting ones. Linear two-source mixing model analysis revealed that fruiting C. macrorhizon plants obtained approximately 73.7 ± 2.0% of their total carbon from their mycorrhizal fungi when the sprouting individuals were used as the 100% carbon gain standard. Our results indicated that despite its leafless status, fruiting plants of C. macrorhizon were capable of fixing significant quantities of carbon. Considering the autotrophic carbon gain increases during the fruiting season, its photosynthetic ability may contribute to fruit and seed production. These results indicate that C. macrorhizon should, therefore, be considered a partially mycoheterotrophic species rather than fully mycoheterotrophic, at least during the fruiting stage.

Dense infraspecific sampling reveals rapid and independent trajectories of plastome degradation in a heterotrophic orchid complex.

Heterotrophic plants provide excellent opportunities to study the effects of altered selective regimes on genome evolution. Plastid genome (plastome) studies in heterotrophic plants are often based on one or a few highly divergent species or sequences as representatives of an entire lineage, thus missing important evolutionary-transitory events. Here, we present the first infraspecific analysis of plastome evolution in any heterotrophic plant. By combining genome skimming and targeted sequence capture, we address hypotheses on the degree and rate of plastome degradation in a complex of leafless orchids (Corallorhiza striata) across its geographic range. Plastomes provide strong support for relationships and evidence of reciprocal monophyly between C.involuta and the endangered C.bentleyi. Plastome degradation is extensive, occurring rapidly over a few million years, with evidence of differing rates of genomic change among the two principal clades of the complex. Genome skimming and targeted sequence capture differ widely in coverage depth overall, with depth in targeted sequence capture datasets varying immensely across the plastome as a function of GC content. These findings will help to fill a knowledge gap in models of heterotrophic plastid genome evolution, and have implications for future studies in heterotrophs.

Infestation of the mycoheterotrophic orchid Yoania japonica by the two-winged fly, Chyliza vittata (Diptera: Psilidae)

Chyliza vittata is known to utilize leaves, stems and underground parts of several leafy and leafless orchids. Compared to the well-recorded feeding habits of C. vittata in Europe, its feeding habits in Japan are poorly studied. Thus, further records of its host plants and the habits of its larvae in Japan are likely to reveal the similarities and differences in its feeding habits in Europe and Japan. The current study reports C. vittata feeding on the stems of the mycoheterotrophic orchid Yoania japonica in central Japan. This study also showed that in spite of the small size of Yoania its reproductive success is not severely reduced when infested with C. vittata, whereas the robust stems of Gastrodia elata, which is its main host plant in Japan, are thought to be a defence against infestation by C. vittata.

Morphology, anatomy, and mycorrhizal fungi colonization in roots of epiphytic orchids of Sempu Island, East Java, Indonesia

Nurfadilah S, Yulia ND, Ariyanti EE. 2016. Morphology, anatomy, and mycorrhizal fungi colonisation in roots of epiphytic orchids of Sempu Island, East Java, Indonesia. Biodiversitas 17: 592-603. Roots of orchids have important role for survival, adaptation, water and nutrient absorption, and as a place of symbiosis with mycorrhizal fungi. The present study aimed to investigate the morphology, anatomy, and mycorrhizal status in roots of orchids of Sempu Island, Indonesia (Ascochilus emarginatus, Taeniophyllum biocellatum, and Thrixspermum subulatum), in relation to their adaptation to their habitat of coastal forests of Sempu Island. These orchids have different morphological characters; Ascochilus emarginatus and Thrixspermum subulatum are leafy orchids, while Taeniophyllum biocellatum is a leafless orchid. The results showed that all orchids have small number of velamen layers (1-2 layers) as an adaptation to the relatively humid condition. Cell wall thickenings of velamen, exodermis, and endodermis are structural adaptation of all orchids to the relatively high intensity of illumination, to reduce water loss because of transpiration. Mycorrhizal fungi colonization which is important for nutrient acquisition occurs in cortical cells. All orchids have differences in their cell shape, size, and specific characters, such as chloroplasts. The leafless Taeniophyllum biocellatum has many chloroplasts in the cortical root cells that support the photosynthesis process, while A. emarginatus and T. subulatum are lack of chloroplasts in their cortical root cells.

Mate‐seeking and oviposition behavior of Chyliza vittata (Diptera: Psilidae) infesting the leafless orchid Gastrodia elata

AbstractThe psilid fly Chyliza vittata is a leaf miner or stem borer of some orchids in Europe and Japan but few studies on its behavior have been published. Here I describe aspects of the reproductive behavior of the species infesting Gastrodia elata, a leafless orchid. Male mate‐seeking behavior occurred on flowering G. elata plants that were attractive to egg‐laden females, and indeed copulation was observed. Although two or more males were commonly seen on an orchid stem without interaction, males occasionally reacted aggressively toward other males. Females laid eggs on the flowers, floral buds or bracts as well as into the flowers, using their “ovipositor”. Almost all orchids studied eventually produced mature capsules; therefore G. elata seemed to suffer limited damage from infestation by C. vittata. Information regarding a natural enemy and pupation habits is also provided.

Taxonomic Notes onDidymoplexiella siamensisandGastrodia peichatieniana, Two Fully Mycoheterotrophic Orchids New to the Flora of Hong Kong

The ephemeral, leafless orchids Didymoplexiella siamensis and Gastrodia peichatieniana are newly recorded from Hong Kong. A lectotype is selected for the former, and the recently described D. denticulata from southern Vietnam is reduced to its synonymy. Full descriptions and global conservation assessments are presented for these hitherto poorly known species.

On the occurrence of an interesting leafless orchid Neottia listeroides Lindl. in Himachal Pradesh, northwestern Himalaya, India

Field explorations in Himachal Pradesh (2002-2010) have resulted in documenting some new distributional records of orchids for the state. They exhibited a variety of life forms (epiphytes/ terrestrials/ lithophytes) and are mostly distributed in the temperate hills. Present communication provides notes on taxonomy, distribution, habitat ecology and conservation of Neottia listeroides Lindl., an interesting leafless orchid in the state.

Implications of Genotypic Diversity and Phenotypic Plasticity in the Ecophysiological Success of CAM Plants, Examined by Studies on the Vegetation of Madagascar1

Abstract: On the basis of δ13C‐values, genotypic diversity and phenotypic plasticity of CAM behaviour in plants of the Malagasy vegetation is surveyed. The study compares CAM patterns performed in the wild on the levels of genera (Kalanchoë [Crassulaceae], Angraecum [Orchidaceae], Lissochilus [Orchidaceae] and Rhipsalis [Cactaceae]), on the level of a family (Didiereaceae) and finally on the level of a common growth form, namely in leafless orchids. For Rhipsalis, also non‐Malagasy species were included in the comparison. The genus Kalanchoë was found to be dominated by species representing the CAM‐physiotype with CO2 fixation taking place only during the night, whereas the CAM/C3‐ and the C3‐physiotypes (with limited intrinsic CAM potential) were less frequent. The opposite holds true for Angraecum. In the genus Rhipsalis, in the Didiereacean family and in the leafless orchids only the CAM‐physiotype is represented. The photosynthetic physiotypes of CAM plants were found to be related to the environmental conditions of the habitat. That is, strong CAM performers are typically abundant in the dry climatic zones or at otherwise dry niches, species of the C3‐physiotype (possibly with weak intrinsic capability of CAM performance) are distributed at humid sites and those of the CAM/C3‐physiotype occupy sites with medium and changing exposure to stress. Phenotypic plasticity of CAM, as indicated by the intraspecific variability of the δ13C‐values, was lower in the CAM‐physiotype compared with the CAM/C3‐physiotype.Our data support the view that strong stress leads to the dominance of highly adapted specialists among the CAM plants, with low phenotypic plasticity of the photosynthetic behaviour, whereas medium stress advances the unfolding of plastic CAM behaviour. Moreover, the data suggest that genera comprising all three physiotypes (Kalanchoë, Angraecum) are dispersed all over Madagascar, whilst groups comprising only strong CAM performers are restricted to limited areas or special types of habitats. This suggests that both genotypic diversity and phenotypic plasticity are important factors for the ecophysiological success of CAM.