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773 results for “Orchid”
Data from: Hybridization and geographic distribution shapes the spatial genetic structure of two co-occurring orchid species
Multiple ecological and life-history traits shape the fine-scale spatial genetic structure (FSGS) of a given population. The occurrence in core versus peripheral populations, levels of outcrossing, pollen and seed dispersal, and hybridization are important biological properties that influence the kinship of individuals within populations. We examined spatial genetic structure within 15 populations of Epidendrum fulgens and E. puniceoluteum distributed along a linear gradient of Brazilian coastal vegetation, including both allopatric and sympatric populations where the two orchid species hybridize. We analyzed 581 mapped specimens using nine simple sequence repeat loci, aiming to investigate how geographic distribution and hybridization shape within-population FSGS. A significant increase in FSGS was found towards peripheral populations, compared to core populations. Analysis of short- and long-distance components of FSGS identified biparental inbreeding and higher levels of FSGS at peripheral populations, when compared to core populations. In contrast, the relatively high density of reproductive adults in core populations potentially leads to highly overlapping seed and pollen movement, decreasing FSGS. Hybridization was an important factor shaping within-population spatial genetic structure at sympatric sites, decreasing the FSGS observed in parental species. Our results indicate that different ecological forces act in concert to create a gradient of FSGS along species distribution ranges, shaped by extensive levels of intra- and interspecific gene exchange.
Data from: Why do mixotrophic plants stay green? A comparison between green and achlorophyllous orchid individuals in situ
Some forest plants adapt to shade by mixotrophy, i.e., they obtain carbon both from photosynthesis and from their root mycorrhizal fungi. Fully achlorophyllous species using exclusively fungal carbon (the so-called mycoheterotrophic plants) have repeatedly evolved from such mixotrophic ancestors. However, adaptations for this evolutionary transition, and the reasons why it has happened a limited number of times, remain unknown. We investigated this using achlorophyllous variants (i.e., albinos) spontaneously occurring in Cephalanthera damasonium, a mixotrophic orchid. In two populations, we compared albinos with co-occurring green individuals in situ. We investigated vegetative traits, namely, shoot phenology, dormancy, CO2 and H2O leaf exchange, mycorrhizal colonization, degree of mycoheterotrophy (using 13C abundance as a proxy), and susceptibility to pathogens and herbivores. We monitored seed production (in natural or experimental crosses) and seed germination. Albinos displayed (1) more frequent shoot drying at fruiting, possibly due to stomatal dysfunctions, (2) lower basal metabolism, (3) increased sensitivity to pathogens and herbivores, (4) higher dormancy and maladapted sprouting, and, probably due to the previous differences, (5) fewer seeds, with lower germination capacity. Over the growing season, green shoots shifted from using fungal carbon to an increasingly efficient photosynthesis at time of fruiting, when fungal colonization reached its minimum. Conversely, the lack of photosynthesis in fruiting albinos may contribute to carbon limitation, and to the above-mentioned trends. With a 103× fitness reduction, albinos failed a successful transition to mycoheterotrophy because some traits inherited from their green ancestors are maladaptive. Conversely, mycoheterotrophy requires at least degeneration of leaves and stomata, optimization of the temporal pattern of fungal colonization and shoot sprouting, and new defenses against pathogens and herbivores. Transition to mycoheterotrophy likely requires progressive, joint evolution of these traits, while a sudden loss of photosynthesis leads to unfit plants. We provide explanations for the evolutionary stability of mixotrophic nutrition and for the rarity of emergence of carbon sinks in mycorrhizal networks. More broadly, this may explain what prevents the emergence of fully heterotrophic taxa in the numerous other mixotrophic plant or algal lineages recently described.
Data from: Disentangling visual and olfactory signals in mushroom-mimicking Dracula orchids using realistic three-dimensional printed flowers
Flowers use olfactory and visual signals to communicate with pollinators. Disentangling the relative contributions and potential synergies between signals remains a challenge. Understanding the perceptual biases exploited by floral mimicry illuminates the evolution of these signals. Here, we disentangle the olfactory and visual components of Dracula lafleurii, which mimics mushrooms in size, shape, color and scent, and is pollinated by mushroom-associated flies. To decouple signals, we used three-dimensional printing to produce realistic artificial flower molds that were color matched and cast using scent-free surgical silicone, to which we could add scent. We used GC-MS to measure scents in co-occurring mushrooms, and related orchids, and used these scents in field experiments. By combining silicone flower parts with real floral organs, we created chimeras that identified the mushroom-like labellum as a source of volatile attraction. In addition, we showed remarkable overlap in the volatile chemistry between D. lafleurii and co-occurring mushrooms. The characters defining the genus Dracula – a mushroom-like, 'gilled' labellum and a showy, patterned calyx – enhance pollinator attraction by exploiting the visual and chemosensory perceptual biases of drosophilid flies. Our techniques for the manipulation of complex traits in a nonmodel system not conducive to gene silencing or selective breeding are useful for other systems.
Data from: Stable epigenetic effects impact adaptation in allopolyploid orchids (Dactylorhiza: Orchidaceae)
Epigenetic information includes heritable signals that modulate gene expression but are not encoded in the primary nucleotide sequence. We have studied natural epigenetic variation in three allotetraploid sibling orchid species that differ radically in geography/ecology. The epigenetic variation released by genome doubling has been restructured in species-specific patterns that reflect their recent evolutionary history, and have an impact on their ecology and evolution, hundreds of generations after their formation. Epigenome scans pinpointed epiloci under divergent selection that correlate with eco-environmental variables, mainly related to water availability and temperature. The stable epigenetic divergence in this group is largely responsible for persistent ecological differences, which then set the stage for species-specific genetic patterns to accumulate in response to further selection and/or drift. Our results strongly suggest a need to expand our current evolutionary framework to encompass a complementary epigenetic dimension when seeking to understand population processes that drive phenotypic evolution and adaptation.
Data from: Limitations on orchid recruitment: not a simple picture
Mycorrhizal fungi have substantial potential to influence plant distribution, especially in specialized orchids and mycoheterotrophic plants. However, little is known about environmental factors that influence the distribution of mycorrhizal fungi. Previous studies using seed packets have been unable to distinguish whether germination patterns resulted from the distribution of appropriate edaphic conditions or the distribution of host fungi, as these cannot be separated using seed packets alone. We used a combination of organic amendments, seed packets, and molecular assessment of soil fungi required by three terrestrial orchid species to separate direct and indirect effects of fungi and environmental conditions on both seed germination and subsequent protocorm development. We found that locations with abundant mycorrhizal fungi were most likely to support seed germination and greater growth for all three orchids. Organic amendments affected germination primarily by affecting the abundance of appropriate mycorrhizal fungi. However, fungi associated with the three orchid species were affected differently by the organic amendments and by forest successional stage. The results of this study help contextualize the importance of fungal distribution and abundance to the population dynamics of plants with specific mycorrhizal requirements. Such phenomena may also be important for plants with more general mycorrhizal associations.
Data from: Genic rather than genome-wide differences between sexually deceptive Ophrys orchids with different pollinators
High pollinator specificity and the potential for simple genetic changes to affect pollinator attraction make sexually deceptive orchids an ideal system for the study of ecological speciation, in which change of flower odour is likely important. This study surveys reproductive barriers and differences in floral phenotypes in a group of four closely related, co-flowering sympatric Ophrys species, and uses a genotyping by sequencing (GBS) approach to obtain information on the proportion of the genome that is differentiated between species. Ophrys species were found to effectively lack post-pollination barriers, but are strongly isolated by their different pollinators (floral isolation), and to a smaller extent, by shifts in flowering time (temporal isolation). Although flower morphology and perhaps labellum coloration may contribute to floral isolation, reproductive barriers may largely be due to differences in flower odour chemistry. GBS revealed shared polymorphism throughout the Ophrys genome, with very little population structure between species. Genome scans for FST outliers identified few markers that are highly differentiated between species and repeatable in several populations. These genome scans also revealed highly differentiated polymorphisms in genes with putative involvement in floral odour production, including a previously identified candidate gene thought to be involved in the biosynthesis of pseudo-pheromones by the orchid flowers. Taken together, these data suggest that ecological speciation associated with different pollinators in sexually deceptive orchids has a genic rather than a genomic basis, placing these species at an early phase of genomic divergence within the 'speciation continuum'.
Data from: Highest genetic diversity at the northern range limit of the rare orchid Isotria medeoloides
Populations in previously glaciated regions are often genetically depauperate in comparison with populations at lower latitudes, due either to bottlenecks experienced in post-glacial colonization, or to contemporary genetic drift in small, peripheral populations. Populations of the rare self-fertilizing North American orchid Isotria medeoloides are largest in the previously glaciated region near the northern range limit, allowing us to examine the role of historical versus contemporary processes in determining population genetic diversity and structure. If contemporary processes predominate, genetic diversity should increase with increasing census size. In contrast, if sequential bottlenecks associated with colonization are paramount, diversity should decrease with latitude and be relatively insensitive to census size. We genotyped 299 individuals from 20 populations at four variable microsatellite loci to contrast genetic diversity and structure for populations in previously glaciated regions versus previously unglaciated regions. Populations were highly inbred (F = 0.95) and highly differentiated (RST = 0.485). Across all sampled populations, genetic diversity decreased and genetic differentiation increased with declining population size. Small southern populations were especially differentiated and genetically depauperate. In the glaciated part of the range, genetic diversity increased as populations approached the northern range limit, demonstrating the centrality of contemporary processes for this post-glacial colonist.
Data from: Morphological, ecological and genetic aspects associated with endemism in the Fly Orchid group
The European genus Ophrys (Orchidaceae) is famous for its insect-like floral morphology, an adaptation for a pseudocopulatory pollination strategy involving Hymenoptera males. A large number of endemic Ophrys species have recently been described, especially within the Mediterranean Basin, which is one of the major species diversity hotspots. Subtle morphological variation and specific pollinator dependence are the two main perceptible criteria for describing numerous endemic taxa. However, the degree to which endemics differ genetically remains a challenging question. Additionally, knowledge regarding the factors underlying the emergence of such endemic entities is limited. To achieve new insights regarding speciation processes in Ophrys, we have investigated species boundaries in the Fly Orchid group (Ophrys insectifera sensu lato) by examining morphological, ecological and genetic evidence. Classically, authors have recognized one widespread taxon (O. insectifera) and two endemics (O. aymoninii from France and O. subinsectifera from Spain). Our research has identified clear morphological and ecological factors segregating among these taxa; however, genetic differences were more ambiguous. Insights from cpDNA sequencing and amplified fragment length polymorphisms genotyping indicated a recent diversification in the three extant Fly Orchid species, which may have been further obscured by active migration and admixture across the European continent. Our genetic results still indicate weak but noticeable phylogeographic clustering that partially correlates with the described species. Particularly, we report several isolated haplotypes and genetic clusters in central and southeastern Europe. With regard to the morphological, ecological and genetic aspects, we discuss the endemism status within the Fly Orchid group from evolutionary, taxonomical and conservation perspectives.
Data from: High levels of effective long-distance dispersal may blur ecotypic divergence in a rare terrestrial orchid
Background: Gene flow and adaptive divergence are key aspects of metapopulation dynamics and ecological speciation. Long-distance dispersal is hard to detect and few studies estimate dispersal in combination with adaptive divergence. The aim of this study was to investigate effective long-distance dispersal and adaptive divergence in the fen orchid (Liparis loeselii (L.) Rich.). We used amplified fragment length polymorphism (AFLP)-based assignment tests to quantify effective long-distance dispersal at two different regions in Northwest Europe. In addition, genomic divergence between fen orchid populations occupying two distinguishable habitats, wet dune slacks and alkaline fens, was investigated by a genome scan approach at different spatial scales (continental, landscape and regional) and based on 451 AFLP loci. Results: We expected that different habitats would contribute to strong divergence and restricted gene flow resulting in isolation-by-adaptation. Instead, we found remarkably high levels of effective long-distance seed dispersal and low levels of adaptive divergence. At least 15% of the assigned individuals likely originated from among-population dispersal events with dispersal distances up to 220 km. Six (1.3%) 'outlier' loci, potentially reflecting local adaptation to habitat-type, were identified with high statistical support. Of these, only one (0.22%) was a replicated outlier in multiple independent dune-fen population comparisons and thus possibly reflecting truly parallel divergence. Signals of adaptation in response to habitat type were most evident at the scale of individual populations. Conclusions: The findings of this study suggest that the homogenizing effect of effective long-distance seed dispersal may overwhelm divergent selection associated to habitat type in fen orchids in Northwest Europe.
Data from: An experimental evaluation of traits that influence the sexual behaviour of pollinators in sexually deceptive orchids
Pollination by sexual deception of male insects is perhaps one of the most remarkable cases of mimicry in the plant kingdom. However, understanding the influence of floral traits on pollinator behaviour in sexually deceptive orchids is challenging, due to the risk of confounding changes in floral odour when manipulating morphology. Here, we investigated the floral traits influencing the sexual response of male Zaspilothynnus nigripes (Tiphiidae) wasps, a pollinator of two distantly related sexually deceptive orchids with contrasting floral architecture, Caladenia pectinata and Drakaea livida. In D. livida the chemical sexual attractant is emitted from the labellum, while in C. pectinata it is produced from the distal sepal tips, allowing manipulative experiments. When controlling for visual cues there was no difference in long distance attraction, though the floral odour of D. livida induced copulation more frequently than that of C. pectinata. The role of colour in pollinator sexual attraction was equivocal, indicating that colour may not be a strong constraint on the initial evolution of sexual deception. The frequency of wasp visitors landing on C. pectinata decreased when the amount of floral odour was reduced, but attempted copulation rates were enhanced when the source of floral odour was associated with the labellum. These latter variables may represent axes of selection that operate across many sexually deceptive species. Nonetheless, the observed variation in floral traits suggests flexibility in how sexual deception can be achieved.
Data from: Ancient mitochondrial gene transfer between fungi and the orchids
The mitochondrial genomes (mitogenomes) of plants are known to incorporate and accumulate DNA from intra- and extracellular donors. Despite the intimate relationships formed between flowing plants (angiosperms) and fungi, lengthy fungal-like sequence has not been identified in angiosperm mitogenomes to date. Here we present multiple lines of evidence documenting horizontal gene transfer (HGT) between the mitogenomes of fungi and the ancestors of the orchids, plants that are obligate parasites of fungi during their early development. We show that the ancestor of the orchids acquired an approximately 270 bp fungal mitogenomic region containing three transfer RNA genes. We propose that the short HGT was later replaced by a second HGT event transferring more than 8 kb and 14 genes from a fungal mitogenome to that of the ancestor of the largest orchid subfamily, Epidendroideae. Our results represent the first evidence of genomic-scale HGT between fungal and angiosperm mitogenomes and demonstrate that the length intergenic spacer regions of angiosperm mitogenomes can effectively fossilize the genomic remains of ancient, non-plant organisms.
Data from: Phylogeographic structure and outbreeding depression reveal early stages of reproductive isolation in the Neotropical orchid Epidendrum denticulatum
Phylogeographic studies provide an important framework for investigating the mechanisms operating during the earliest stages of speciation, as reproductive barriers can be examined among divergent lineages in a geographic context. We investigated the evolution of early stages of intrinsic postmating isolation among different populations and lineages of Epidendrum denticulatum, a Neotropical orchid distributed across different biomes in South America. We estimated genetic diversity and structure for both nuclear and plastid markers, using a haplotype network, differentiation tests, Bayesian assignment analysis, and divergence time estimates of the main lineages. Reproductive barriers among divergent lineages were examined by analyzing seed viability following reciprocal crossing experiments. Strong plastid phylogeographic structure was found, indicating that E. denticulatum was restricted to multiple refuges during South American forest expansion events. In contrast, significant phylogeographic structure was not found for nuclear markers, suggesting higher gene flow by pollen than by seeds. Large asymmetries in seed set were observed among different plastid genetic groups, suggesting the presence of polymorphic genic incompatibilities associated with cytonuclear interactions. Our results confirm the importance of phylogeographic studies associated with reproductive isolation experiments and suggest an important role for outbreeding depression during the early stages of lineage diversification.
Data from: A novel case of autogamy and cleistogamy in Dendrobium wangliangii: a rare orchid distributed in the dry-hot valley
Dendrobium wangliangii is an epiphytic orchid distributed in the Jinshajiang dry-hot valley in Luquan County, Yunnan Province, China. Most Dendrobium spp. typically have a low fruit set, but this orchid shows a higher fruit set under natural conditions despite the lack of effective pollinators. The pollination biology of the critically endangered D. wangliangii was investigated in this study. A fruit set rate of 33.33±4.71% was observed after bagging treatment in 2017 and a high fruit set rate (65.72±4.44% in 2011; 50.79±5.44% in 2017) was observed under natural conditions, indicating that D. wangliangii is characterized by spontaneous self-pollination. The anther cap prevented the growing pollinium, thus the pollinium slid down and reached the stigmatic cavity, leading to autogamous self-pollination. Specifically, 51.50% of 162 unopened flowers (total 257 flowers) of this Dendrobium species under extreme water-deficit conditions developed into fruits, suggesting the presence of cleistogamy in D. wangliangii. Here, cleistogamy may represent the primary mode of pollination for this orchid. Spontaneous self-pollination and specific cleistogamous autogamy could represent major adaptions to the drought and pollinator-scarce habitat in the Jinshajiang dry-hot valley.
Data from: Climate, physiological tolerance, and sex-biased dispersal shape genetic structure of Neotropical orchid bees
Understanding the impact of past climatic events on the demographic history of extant species is critical for predicting species' responses to future climate change. Paleoclimatic instability is a major mechanism of lineage diversification in taxa with low dispersal and small geographic ranges in tropical ecosystems. However, the impact of these climatic events remains questionable for the diversification of species with high levels of gene flow and large geographic distributions. In this study, we investigate the impact of Pleistocene climate change on three Neotropical orchid bee species (Eulaema bombiformis, E. meriana and E. cingulata) with transcontinental distributions and different physiological tolerances. We first generated ecological niche models to identify species-specific climatically stable areas during Pleistocene climatic oscillations. Using a combination of mitochondrial and nuclear markers, we inferred calibrated phylogenies and estimated historical demographic parameters to reconstruct the phylogeographic history of each species. Our results indicate species with narrower physiological tolerance experienced less suitable habitat during glaciations and currently exhibit strong population structure in the mitochondrial genome. However, nuclear markers with low and high mutation rates show lack of association with geography. These results combined with lower migration rate estimates from the mitochondrial than the nuclear genome suggest male-biased dispersal. We conclude that despite large effective population sizes and capacity for long-distance dispersal, climatic instability is an important mechanism of maternal lineage diversification in orchid bees. Thus, these Neotropical pollinators are susceptible to disruption of genetic connectivity in the event of large-scale climatic changes.
Data from: Germination patterns in three terrestrial orchids relate to abundance of mycorrhizal fungi
1. The spatial distribution of plants, which is often generated by patterns of seed recruitment, is an important determinant of population dynamics, especially for orchids with seeds that must be exposed to appropriate mycorrhizal fungi. 2. We compared the distribution and abundance of target mycorrhizal fungi detected in the soil using DNA-based molecular techniques and germination in seed packets of Goodyera pubescens, Liparis liliifolia, and Tipularia discolor. 3. We further examined Tulasnella spp. associated with G. pubescens to determine whether areas with abundant host fungi resulted from multiple genets of the same species or from a single widespread fungal genet. 4. We found that target fungi were more likely to be detected using soil DNA assays than by seed germination. Based on soil DNA, fungi were more widespread than suggested by seed germination, which most often reflected the presence of abundant mycorrhizal fungi in the soil. Fungi were more likely to be abundant close to established orchids. Established plants of G. pubescens that were <50cm apart associated with a single abundant fungal genet, while those >50 cm apart associated with multiple fungal genets. 5. Synthesis. This study demonstrates the importance of using multiple methods to detect the distribution and abundance of target fungi and suggests that fungal 'hot spots' may be keys to the dynamics of orchid populations.
FIGURES 3241. Tenuipalpus orchidofilo n in A new species of Tenuipalpidae (Acari: Prostigmata) on orchid from Brazil
FIGURES 3241. Tenuipalpus orchidofilo n. sp., protonymph. 32, Dorsum of idiosoma; 33, venter of idiosoma; 34, dorsum of leg I; 35, venter of leg I; 36, dorsum of leg II; 37, venter of leg II; 38, dorsum of leg III; 39, venter of leg III; 40, dorsum of leg IV; 41, venter of leg IV.
FIGURES 2231. Tenuipalpus orchidofilo n in A new species of Tenuipalpidae (Acari: Prostigmata) on orchid from Brazil
FIGURES 2231. Tenuipalpus orchidofilo n. sp., deutonymph. 22, Dorsum of idiosoma; 23, venter of idiosoma; 24, dorsum of leg I; 25, venter of leg I; 26, dorsum of leg II; 27, venter of leg II; 28, dorsum of leg III; 29, venter of leg III; 30, dorsum of leg IV; 31, venter of leg IV.
FIGURES 1221. Tenuipalpus orchidofilo n in A new species of Tenuipalpidae (Acari: Prostigmata) on orchid from Brazil
FIGURES 1221. Tenuipalpus orchidofilo n. sp., male. 12, Dorsum of idiosoma; 13, venter of idiosoma; 14, dorsum of leg I; 15, venter of leg I; 16, dorsum of leg II; 17, venter of leg II; 18, dorsum of leg III; 19, venter of leg III; 20, dorsum of leg IV; 21, venter of leg IV.
FIGURES 4249. Tenuipalpus orchidofilo n in A new species of Tenuipalpidae (Acari: Prostigmata) on orchid from Brazil
FIGURES 4249. Tenuipalpus orchidofilo n. sp., larva. 42, Dorsum of idiosoma; 43, venter of idiosoma; 44, dorsum of leg I; 45, venter of leg I; 46, dorsum of leg II; 47, venter of leg II; 48, dorsum of leg III; 49, venter of leg III.
FIGURES 111. Tenuipalpus orchidofilo n in A new species of Tenuipalpidae (Acari: Prostigmata) on orchid from Brazil
FIGURES 111. Tenuipalpus orchidofilo n. sp., female. 1, Dorsum of idiosoma; 2, Venter of gnathosoma; 3, venter of idiosoma; 4, dorsum of leg I; 5, venter of leg I; 6, dorsum of leg II; 7, venter of leg II; 8, dorsum of leg III; 9, venter of leg III; 10, dorsum of leg IV; 11, venter of leg IV.
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