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![Inflorescences of 12 representative members of the four clades studied. A, Pseudorchis albida . B, Galearis spectabilis . C, Platanthera bifolia . D, Gymnadenia conopsea . E, Dactylorhiza viridis . F, D. sambucina . G, Anacamptis morio . H, A. fragrans . I, A. pyramidalis . J, Orchis punctulata . K, O. militaris . L, O. spitzelii . Scale: horizontal axis of image, 22 mm. [All images R. M. Bateman except B (O. W. Gupta and F. C. Swope), C and E (D. M. T. Ettlinger)].](profile/Mathew-Box/publication/215811216/figure/fig1/AS:276502970159117@1442934854021/Inflorescences-of-12-representative-members-of-the-four-clades-studied-A-Pseudorchis.png)
Inflorescences of 12 representative members of the four clades studied. A, Pseudorchis albida . B, Galearis spectabilis . C, Platanthera bifolia . D, Gymnadenia conopsea . E, Dactylorhiza viridis . F, D. sambucina . G, Anacamptis morio . H, A. fragrans . I, A. pyramidalis . J, Orchis punctulata . K, O. militaris . L, O. spitzelii . Scale: horizontal axis of image, 22 mm. [All images R. M. Bateman except B (O. W. Gupta and F. C. Swope), C and E (D. M. T. Ettlinger)].
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Floral nectar spurs are widely considered to influence pollinator behaviour in orchids. Spurs of 21 orchid species selected from within four molecularly circumscribed clades of subtribe Orchidinae (based on Platanthera s.l., Gymnadenia–Dactylorhiza s.l., Anacamptis s.l., Orchis s.s.) were examined under light and scanning electron microscopes in or...
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... Fig. 7N), outward (e.g. Figs 7I, 9A) or even both (e.g. Fig 7M). The number and size of the secondary veins relative to the primary vein differs considerably among species. In Gymnadenia conopsea , the primary vein is difficult to distinguish from the secondary veins (it does not form ridges) and there are approximately six secondary veins (Figs 7B, 8D, G). Gymnadenia conopsea also appears to be the most distinct species with respect to thickness and anatomy of the spur wall (Fig. 7B). Although the overall diameters of the spurs vary considerably among the figured species, their wall thickness (measured as both distance and cell number, at a tangent of 45° relative to the two strands of the main vein) is remarkably consistent. Almost all species have spur walls that are typically four cells thick, ranging from c. 75 m m in Pseudorchis albida (L.) A.Löve & D.Löve to c. 140 m m in several species of Anacamptis , Orchis and Dactylorhiza sambucina (Fig. 7). Within Orchis , spur walls on the anthropomorphic species ( O. punctulata , O. militaris ) are thinner walled than the remainder: typically three cells and 110–125 m m thick vs. four cells and 132–140 m m thick. Similarly, within Dactylorhiza , D. viridis and D. fuchsii appear to have thinner spur walls than D. sambucina : three cells and 80–95 m m vs. four to five cells and 140 m m. In contrast, Gymnadenia conopsea packs six to seven layers of cells within a wall thickness of 110 m m, an average width relative to other sampled species. I NFERRING FUNCTIONAL MORPHOLOGY Although the occurrences of papillae and striations both reveal considerable levels of homoplasy, both appear to be under some phylogenetic influence. Most notably, species pairs from each of the four clades have similar micromorphologies and degrees of nectar secretion: Platanthera bifolia and P. chlorantha (Bateman et al. , 2009), Gymnadenia conopsea and G. odoratissima (Bateman et al. , 2006), Anacamptis coriophora and A. fragrans (Bateman et al. , 2003; Kretzschmar, Eccarius & Dietrich, 2007) and Orchis punctulata and O. militaris (Kretzschmar et al. , 2007; Bateman, Smith & Fay, 2008). Although all correlations among the occurrence of nectar, papillae and striations are imperfect (Table 2), the positive correlation between nectar and papillae is strong and the negative correlation between nectar and striations, although weaker, is intriguing. The closest that one can achieve to an absolute correlation statement is to note that, of the five study species that generate substantial quantities of nectar, only one has pronounced striations and four have comparatively high densities of medium–long papillae, averaging 50–80 m m in length (Table 1). Moreover, data are equivocal for the single exception, Gymnadenia frivaldii , which appears to maintain a reservoir but to lack papillae (cf. Bateman et al. , 2006). The most obvious inference gained from the accumulated data is that papillae facilitate the secretion of nectar by increasing the surface area of the interior of the spur. However, this hypothesis would suggest that species producing only modest amounts of nectar (i.e. categorized as ‘trace’ in Table 1) should also have prominent papillae, whereas in fact only a minority of the study species are so well endowed. A better explanation may be rooted in the observations of Stpiczynska (2003a, b) that the spurs of the nectar-rich species Platanthera chlorantha reabsorb nectar, prioritizing the dominant sugar (sucrose). Significantly, reabsorption is achieved rapidly and is conducted primarily by the interior epidermis; we suspect that the long papillae would be particularly advantageous to this process by greatly increasing the surface area of the spur interior. However, we are surprised that the length and density of papillae do not appear to be influenced by proximity to the primary vein (Figs 8A, B, 9A, B). Estimates of the cost of nectar production by monocot flowers, measured in terms of the proportion of the total energy content of the flower, range from 3% for Pontederia cordata L. (Harder & Barrett, 1995) to 37% in Blandfordia nobilis Sm. (Pyke, 1991); estimates for most other species are closer to the higher figure. Given the large amounts of nectar generated by ‘reservoir’ orchids such as Platanthera chlorantha and Gymnadenia conopsea , reabsorption of sugars from the copious nectar would represent a substantial energy saving. However, there is a cautionary lesson to be learned from three study species that are nectarless but produce medium–large papillae: two from clade B ( Dactylorhiza fuchsii and D. sambucina ) and one from clade D ( Orchis spitzelii ). One might argue that these species evolved relatively recently from nectariferous ancestors and have not yet lost their redundant papillae, but this hypothesis is not supported by their phylogenetic context; they occupy relatively long terminal branches and are nested among non-rewarding species (Fig. 1). Alternatively, they could conceivably function as osmophores (e.g. Vogel, 1990), fulfilling the key function of providing the olfactory cue that first attracts the insects. However, osmophores are typically presented on the exterior of the labellum (e.g. Dafni, 1987; Paulus, 2006; Schiestl & Cozzolino, 2008), facilitating dispersal of the attractant chemi- cals; in addition, these are more likely to be detected by the antennae of the insect than by its proboscis. Although it is unlikely that scent production is the function of the papillae in the spur, the answer could still lie in the nature of the interactions ...
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... to mate with flowers (e.g. Paulus, 2006; Devey et al. , 2008; Schiestl & Cozzolino, 2008), and the more common form of deceit, food deceit, when the orchid promises, but fails to deliver, a nectar reward (Scopece et al. , 2007; Schlüter & Schiestl, 2008). Yet other orchids have shifted their breeding system, preferring instead the genetic impoverishment that inevitably accompanies autogamy and/or apomixis (e.g. Hollingsworth et al. , 2006). Some studies of these four contrasting pollination syndromes (nectarifery, food deceit, sexual deceit, autogomy/apomixis) have gathered detailed observations on specific case studies in attempts to understand their physiological and ecological consequences (e.g. Gigord, Macnair & Smithson, 2001; Maad & Alexandersson, 2004; Little, Dieringer & Romano, 2005), whereas others have pursued broad-brush surveys of related taxa (Cozzolino & Widmer, 2005; Scopece et al. , 2007; Cozzolino & Scopece, 2008), increasingly guided by molecular phylogenetic studies. The most intensively studied tribe has been Orchideae Dressler & Dodson, which reaches its maximum diversity in the Mediterranean-climate biomes of southern Europe, Australia and South Africa. Here, we have used a well-sampled molecular phylogenetic survey of Orchideae subtribe Orchidinae Dressler & Dodson (Bateman et al. , 2003; Bateman, 2009a) as a guide to selecting several closely related species of nectar-rewarding and food-deceptive species from the northern hemisphere for morphological comparison. Our primary objective was to compare the micromorphology of mature specimens of the single tubular spur that forms as an invagination of the labellum close to its junction with other organs (Rudall & Bateman, 2002; Box et al. , 2008; see also Golz, Keck & Hudson, 2002). Except for the closely related genera Serapias L. and Ophrys L., spurs occur in the flowers of every species of Orchidinae (albeit reduced to a near-vestigial condition in a few phylogenetically scattered species: Rudall & Bateman, 2002; Bateman et al. , 2003; Box et al. , 2008) ( Fig. 1). The nectar- producing tissue within the spur is the abaxial (internal) epidermis, which is typically cuticularized and encloses a vascularized parenchyma (Fahn, 1979; Stpiczynska, 2003b). Thus, the spur is of particular interest as it is widely regarded as playing a key role in guiding the behaviour of potential pollinators once they have made physical contact with the orchid flower and has therefore been implicated as a major cause of the species richness of the family (e.g. Rudall & Bateman, 2002; Box et al. , 2008). In developing this project, we sought to identify and attempt to explain any correlations between micromorphological features of the internal epidermis of the spur, visualized using both the light and scanning electron microscopes, and the presence and amount of nectar in the spur (Bell, 2006). Four major clades of Orchidinae in the nuclear ribosomal DNA (nrDNA) internal transcribed spacer (ITS) phylogenetic analysis of Bateman et al. (2003) were selected for study and between four and seven species were examined in each of clades A–D (Fig. 2, Table 1). All four of these clades contain both nectariferous and nectarless species, although only nectarless species from clade D were studied here [ Orchis anthropophora (L.) All. was not examined: Fig. 2D]. The majority of the study species, including all species in clades C ( Anacamptis Rich. s.l. ) and D ( Orchis L. s.s. ), were examined specifically for this project by Bell (2006), the materials being drawn from the spirit collection at the Royal Botanic Gardens, Kew (K): details of the specimens are given in the Supporting Information (Appendix S1). Bell’s (2006) study of group B ( Gymnadenia R.Br. – Dactylorhiza Neck. ex Nevski) overlapped in species sampling with a detailed examination of floral ontogeny of five of the species by Box et al. (2008), allowing cross-referencing of observations between the two projects. Group A (the Platanthera Rich. clade) was scored for the requisite characters by pooling data from several recent combined molecular and morphological studies performed by Bateman and colleagues on the constituent genera of the group: Pseudorchis Ség. (Bateman, Rudall & James, 2006), Neolindleya Kraenzl. (Efimov, Lauri & Bateman, 2009), Galearis Raf. (present study) and Platanthera s.l. (Bateman, James & Rudall, 2009; see also Stpiczynska, 2003a, b). We were also able to compare our observations on Gymnadenia s.s. with those of Stpiczynska and colleagues (Stpiczynska & Matusiewicz, 2001; Stpiczynska, 2001). Two accessions were examined for most study species and two flowers were excised from each inflo- rescence. Accessions had been stored in Kew Mix [53% industrial methylated spirit (98/99% total alco- hols): 37% water: 5% formaldehyde solution (38%w/ w): 5% glycerol]. Flowers were given successive 1-h immersions in 70%, 80%, 90% and 100% ethanol prior to mounting. Specimens for light microscopy (LM) underwent nine rinses from 100% ethanol to 100% histoclear in a tissue processor, before being embedded in para- plast at 62 °C for 3 weeks. Transverse sections of each spur were cut to 14 m m thickness in a rotary micro- tome, attached to glass slides using Haupt’s adhesive, stained with safranin and alcian blue and mounted under a coverslip in di-n-butyle phthalate in xylene (DPX). Slides were examined under a Leica ...
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... & Bateman, 2002;Box et al., 2008; see also Golz, Keck & Hudson, 2002). Except for the closely related genera Serapias L. and Ophrys L., spurs occur in the flowers of every species of Orchidinae (albeit reduced to a near-vestigial condition in a few phylogenetically scattered species: Rudall & Bateman, 2002;Bateman et al., 2003;Box et al., 2008) (Fig. 1). The nectarproducing tissue within the spur is the abaxial (internal) epidermis, which is typically cuticularized and encloses a vascularized parenchyma (Fahn, 1979;Stpiczynska, 2003b). Thus, the spur is of particular interest as it is widely regarded as playing a key role in guiding the behaviour of potential pollinators once they ...
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... five study species of Orchis s.s. that constitute Group D are characterized by nectarless, mediumlength spurs (Table 1, Fig. 6). The two members of Orchis L. subgenus Orchis, O. punctulata Steven ex Lindl. ...
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... of the cost of nectar production by monocot flowers, measured in terms of the proportion of the total energy content of the flower, range from 3% for Pontederia cordata L. (Harder & Barrett, 1995) to 37% in Blandfordia nobilis Sm. (Pyke, 1991); estimates for most other species are closer to the higher figure. Given the large amounts of nectar generated by 'reservoir' orchids such as Platanthera chlorantha and Gymnadenia conopsea, reabsorption of sugars from the copious nectar would represent a substantial energy saving. ...
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... sambucina) and one from clade D (Orchis spitzelii). One might argue that these species evolved relatively recently from nectariferous ancestors and have not yet lost their redundant papillae, but this hypothesis is not supported by their phylogenetic context; they occupy relatively long terminal branches and are nested among non-rewarding species (Fig. 1). Alternatively, they could conceivably function as osmophores (e.g. Vogel, 1990), fulfilling the key function of providing the olfactory cue that first attracts the insects. However, osmophores are typically presented on the exterior of the labellum (e.g. Dafni, 1987;Paulus, 2006;, facilitating dispersal of the attractant chemicals; in ...
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Many orchids produce nectar in order to attract insects. However, in the European orchids there are a considerable number of orchids which produce no nectar. Why would an orchid shift from reward to no reward, as this pollination mode clearly attracts less insects? We will discuss this on the basis of two non-rewarding orchid genera, Himantoglossum...
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... It is also worth considering the likely morphological transitions that dictated the origin of the genus Ophrys. All genera closely related to Ophrys [20,84] have labella that are largely two-dimensional, the third dimension being confined to the simple curvature of the lateral margins, except that, proximally, the labella of genera such as Neotinea, Himantoglossum and Anacamptis are consistently invaginated into an elongate cylindrical spur that may or may not secrete nectar [85]. We suspect that a key stage in the emergence and initial diversification of the genus Ophrys was the evolutionary loss of that spur, because it liberated the labellum to develop much more complex three-dimensional topographiestopographies that become evident only after the labellum inverted from concave to convex during the opening of the bud [3] (Figures 2 and 3). ...
Simple Summary: Our frequently deployed approach to optimally circumscribing species requires large-scale field sampling within and between populations for large numbers of morphometric characters, followed by multivariate ordinations to objectively seek discontinuities (or, failing that, zones of limited overlap) among sets of populations considered to represent species. Corresponding boundaries are sought in DNA-based outputs, either phylogenies or preferably ordinations based on population genetic data. Herein, we analyse within a molecular phylogenetic framework detailed morphometric data for the charismatic bee orchids (Ophrys), seeking a 'mesospecies' species concept that might provide a compromise between the nine 'macrospecies' recognised primarily through DNA barcoding and the several hundred 'microspecies' recognised primarily through perceived pollinator specificity. Our analyses failed to find robust groupings that could be regarded as credible mesospecies, instead implying that each macrospecies constitutes a morphological continuum. This problematic result encouraged us to reappraise both our morphometric approach and the relative merits of the contrasting macrospecies and microspecies concepts, and to reiterate the key role played by genetics in species circumscription. Abstract: Despite (or perhaps because of) intensive multidisciplinary research, opinions on the optimal number of species recognised within the Eurasian orchid genus Ophrys range from nine to at least 400. The lower figure of nine macrospecies is based primarily on seeking small but reliable discontinuities in DNA 'barcode' regions, an approach subsequently reinforced and finessed via high-throughput sequencing studies. The upper figure of ca. 400 microspecies reflects the morphological authoritarianism of traditional taxonomy combined with belief in extreme pollinator specificity caused by reliance on pollination through pseudo-copulation, enacted by bees and wasps. Groupings of microspecies that are less inclusive than macrospecies are termed mesospecies. Herein, we present multivariate morphometric analyses based on 51 characters scored for 457 individual plants that together span the full morphological and molecular diversity within the genus Ophrys, encompassing 113 named microspecies that collectively represent all 29 mesospecies and all nine macrospecies. We critique our preferred morphometric approach of accumulating heterogeneous data and analysing them primarily using principal coordinates, noting that our conclusions would have been strengthened by even greater sampling and the inclusion of data describing pseudo-pheromone cocktails. Morphological variation within Ophrys proved to be exceptionally multidimensional, lacking strong directional trends. Multivariate clustering of plants according to prior taxonomy was typically weak, irrespective of whether it was assessed at the level of macrospecies, mesospecies or microspecies; considerable morphological overlap was evident even between subsets of the molecularly differentiable macrospecies. Characters supporting genuine taxonomic distinctions were often sufficiently subtle that they were masked by greater and more positively correlated variation that reflected strong contrasts in flower size, tepal colour or, less often, plant size. Individual macrospecies appear to represent morphological continua, within which taxonomic divisions are likely to prove arbitrary if based exclusively on morphological criteria and adequately sampled across their geographic range. It remains unclear how much of the mosaic of subtle character variation among the microspecies reflects genetic versus epigenetic or non-genetic influences and what proportion of any contrasts observed in gene frequencies can be attributed to the adaptive microevolution that is widely considered to dictate speciation in the genus. Moreover, supplementing Biology 2023, 12, 136. https://doi.org/10.3390/biology12010136 https://www.mdpi.com/journal/biology Biology 2023, 12, 136 2 of 52 weak morphological criteria with extrinsic criteria, typically by imposing constraints on geographic location and/or supposed pollinator preference, assumes rather than demonstrates the presence of even the weakest of species boundaries. Overall, it is clear that entities in Ophrys below the level of macrospecies have insufficiently structured variation, either phenotypic or genotypic, to be resolved into discrete, self-circumscribing ("natural") entities that can legitimately be equated with species as delimited within other less specialised plant genera. Our search for a non-arbitrary (meso)species concept competent to circumscribe an intermediate number of species has so far proven unsuccessful.
... Wettewa et al. 2020)allopolyploid complexes of putative species that are difficult to distinguish both phenotypically and genotypically. Both Gymnadenia and Platanthera have fragrant flowers that offer substantial nectar rewards in elongate labellar spurs (Bell et al. 2009); these features best fit the majority of Gymnadenia and Platanthera species for lepidopteran pollinators (Claessens and Kleynen 2011). Both genera have also been the subjects of fairly large-scale molecular and morphometric studies (Bateman et al. 2013;Valuyskikh et al. 2019;Bateman et al. 2021b). ...
Cryptic species are organisms which look identical, but which represent distinct evolutionary lineages. They are an emerging trend in organismal biology across all groups, from flatworms, insects, amphibians, primates, to vascular plants. This book critically evaluates the phenomenon of cryptic species and demonstrates how they can play a valuable role in improving our understanding of evolution, in particular of morphological stasis. It also explores how the recognition of cryptic species is intrinsically linked to the so-called 'species problem', the lack of a unifying species concept in biology, and suggests alternative approaches. Bringing together a range of perspectives from practicing taxonomists, the book presents case studies of cryptic species across a range of animal and plant groups. It will be an invaluable text for all biologists interested in species and their delimitation, definition, and purpose, including undergraduate and graduate students and researchers.
... The sepal and petal papillae may be associated with tactile function to guide or facilitate the movement of insects (Davies and Turner, 2004;Costa et al., 2017) or, more often, fragrance-secreting osmophores may be found on the labellum (Teixeira et al., 2004). When present in the labellum spur, they may have a secretory function similar to that of Aeridinae species (Stpiczynska et al., 2011) and are positively related to the presence of nectar, as in Orchidinae (Bell et al., 2009). However, trichomes or papillae in the spur or cuniculus may not be secretory (Smidt et al., 2006;Silva-Pereira et al., 2007;Davies and Stpiczynska, 2007) and can play an important role in deception (Bell et al., 2009). ...
... When present in the labellum spur, they may have a secretory function similar to that of Aeridinae species (Stpiczynska et al., 2011) and are positively related to the presence of nectar, as in Orchidinae (Bell et al., 2009). However, trichomes or papillae in the spur or cuniculus may not be secretory (Smidt et al., 2006;Silva-Pereira et al., 2007;Davies and Stpiczynska, 2007) and can play an important role in deception (Bell et al., 2009). Therefore, the micromorphological diversity of flowers and their interaction with pollinators influence the reproductive success of the plant and could also be taxonomically important (Davies and Stpiczynska, 2007;Whitney et al., 2009b;Alcorn et al., 2012;Nunes et al., 2014Nunes et al., , 2015Nunes et al., , 2017. ...
... The morphological variation is closely related to the adaptation to different species of pollinators (Hodges, 1997;Bell et al., 2009;Kramer and Hodges, 2010), in addition to being a nectar-secreting structure with a reward for visitors (Singer and Sazima, 2001). In the spur, the presence of papillae (M. ...
Neotropical Goodyerinae has a problematic taxonomic history based on minor morphological differences in flowers. Recently, the species of the genus Aspidogyne have been transferred to Microchilus because of strong phylogenetic evidence. Our goal was to identify anatomical and micromorphological characteristics of Microchilus flowers that could assist in the morphological characterization of the genus. The labellum presented with up to four papillae types and unicellular papilliform trichomes that have a probable tactile and fragrance-secreting function. Secretory structures were structured in two or four strands, prominent or non-prominent in the spur cavity. The secretory tissue contained amyloplasts and a dense cytoplasm with an abundance of organelles, indicating intense metabolic activity. Trichomes were present in most species. Cells with secretory characteristics present on the sepals and petals were likely to be fragrance-secreting structures. The secretory structures inside the spurs differ in number, structure, and position between species and are responsible for the granulocrine secretion that crosses the fissured cuticle.
... As highlighted by histochemical tests, the secretory/osmophoric activity is mainly accomplished by labellar papillae. The long spur has the role of visual attraction in the deceit of pollinators by mimicking spurs or other structures typical of rewarding species [69]. As stated by Figueiredo and Pais [74], Stpiczyńska and Matusiewicz [75] and Naczk et al. [70], components being part of the floral fragrance belong to plastoglobuli which can be present in osmophores. ...
... ,b), while O. provincialis presented more or less protuberant epidermal cells as already stated by Bell et al.[69] (Figure 2c,i). In O. patens, two epidermal protuberances were also observed: one near the spur entrance and another one with elongated papillae positioned near the spur apex(Figure 2a, arrows). ...
Hybridization can often lead to the formation of novel taxa which can have traits that resemble either or both parental species. Determining the similarity of hybrid traits to parental taxa is particularly important in plant conservation, as hybrids that form between rare and common taxa may more closely resemble a rare parental species, thereby putting the rare parental taxon at further risk of extinction via increased backcrossing and introgression. We investigated the floral (morpho-logical and chemical) traits and orchid mycorrhizal (OrM) fungal associations of the endangered orchid Orchis patens, its more common sister species O. provincialis, and their natural hybrid O. × fallax in natural sympatric populations. We found that both morphological and chemical floral traits of O. × fallax are shared by the parents but are more similar to O. patens than O. provincialis. OrM fungi were shared among all three taxa, indicating that the availability of OrM fungi should not represent a barrier to establishment of individuals of any of these taxa. These results suggest that O. × fallax may be able to expand its distribution within a similar niche to O. patens. This highlights the importance of quantifying differences between hybrids and parental taxon in species conservation planning.
... Nevertheless, it should be stressed that in Orchidaceae, in order to save resources and increase pollination success, deception is also common. For example, in certain European genera such as e.g., Dactylorhiza, Anacamptis and Orchis (Bell et al., 2009), as well as in some species of neotropical Epidendrum e.g., E. fulgens (Moreira, Fuhro & Isaias, 2008), the nectaries are devoid of nectar and are represented by floral spurs and a cuniculus, respectively. Furthermore, in these examples, the inner epidermis bears trichomes similar to those present in nectariferous species, and these trichomes probably provide tactile stimuli that deceive pollinators. ...
Barkeria scandens and B. whartoniana are endangered, endemic taxa from Mexico. They are epiphytes adapted to dry habitats. Since these plants are xerophytic, their flowers were investigated for structural adaptations to nectar secretion. The flowers of both species are structurally similar, and contrary to most claims for the genus, have functional floral nectaries comprising a nectary chamber and a narrow tubular cuniculus. Nectar is present in both these structures, and contains sugars and lipid-like compounds. The nectary tissue is composed of a single-layered epidermis overlying 1–2 layers of subepidermal secretory parenchyma. The outer tangential wall of the epidermal cells is thick and multi-layered, whereas the cuticle, which often shows blistering, is lamellate and possesses micro-channels. Lipid-like material occurs both between the microfibrils of the cell wall and in the micro-channels. Robust secretory tissue, thick cell walls, and lipid-like nectar components limit nectar evaporation. Moreover, the rigidity of the nectary potentially makes it possible for red-flowered B. scandens to switch from entomophily to ornithophily.
... The invaginated form toward the proximal end forms a spur-like structure. 31 The labellum/lip is the modified petal that is usually involved in false signals. The modification of the labellum in orchids allows several tactics such as pseudocopulation, pseudo hormone chemicals, rotten smells, and even kettle traps (which falsely offers food) in the Phalaenopsis [slipper orchids). ...
Bee orchids have long been an excellent example of how dishonest signal works in plant-animal interaction. Many studies compared the flower structures that resemble female bees, leading toward pseudo-copulation of the male bees on the flower. Using Machine Learning, we tested whether nature is capable of besting artificial intelligence. A total of 2000 images of related bees, wasps, and Ophrys sp. were collected from the Google Image Repository. Unsuitable images were later filtered out manually, leaving a total of 995 images in the final selection. 80% of these images were used to build a supervised model using Logistic Regression, while the model accuracy was tested using 20% of the remaining images. Based on our results using Wolfram Mathematica, the Ophrys is not capable of fooling artificial intelligence. The accuracy, accuracy baseline, mean cross-entropy, Area Under ROC (receiver operating characteristic curve) curve (AUC) and the confusion matrix gave excellent image classification. However, we can now show the key points and highlights of the images and how the structures closely resemble actual bees using the SURF method. Rather than just a descriptive method, ML learning has enabled a more quantitative approach. Since this is a simple test, we encourage other scientists to adopt our approach using a larger dataset and better database samples.
... In contrast, populations of short-spurred species do not maintain a minority of long-spurred plants, suggesting that any transition from short to long spurs, such as that postulated below G. densiflora in the RAD-seq tree (Fig. 2b), would presumably take place through gradual progressive elongation, most likely driven by drift and/or directional or disruptive selection. Admittedly, labellar spur length reflects a complex interaction of genetic, epigenetic, ontogenetic and ecophenotypic influences (Bateman & Sexton, 2008;Bell et al., 2009;Box et al., 2008). Nonetheless, I find encouragement in the technological precision of evolutionarydevelopmental studies such as Kellenberger et al. (2019), who successfully pinned down a major colour shift in the nigritellan species G. rhellicani to a mutation of a single base-pair; the mutation introduced a novel stop codon that in turn interrupted a biochemical pathway underpinning pigment formation. ...
Recent phylogenetic trees of the phenotypically diverse Eurasian orchid genus Gymnadenia s.l., based on Sanger sequencing of nrITS and next-generation RAD-seq data, largely agree on species boundaries but disagree radically regarding relationships among those species. Moreover, both contrasting topologies receive support from a recent transcriptome study. But these genetic studies are not matched by a taxonomically comprehensive analysis of phenotype. Population-level in situ morphometric analyses of 41 characters for 150 plants spanning seven putative species are used to determine overall phenetic similarities of the species, thereby allowing both phenotypic species circumscription and comparison of estimated phenotypic and genotypic disparities. The three widely recognized short-spurred lineages prove highly morphometrically divergent from each other and from the long-spurred species, which differ from each other only subtly. Phenetic disparity correlates strongly with genetic disparity for RAD-seq data but not with that for nrITS data. The RAD-seq topology is appealing because it implies a fractal evolutionary pattern, but it also requires that later-divergent, recently evolved species are far more geographically widespread than their putative antecedents. Current knowledge of this intensively studied genus allows stronger conclusions on circumscription of taxa than on determining their evolutionary relationships; the clade is unequivocally a single genus that, on present evidence, consists of approximately 12 species. I emphasize the importance of rigorously describing and analysing phenotype, of tree rooting, and of critically appraising reconstructed phylogenies, irrespective of the robustness of the data and the determination with which they are analysed.
... The most distinctive features of a Gymnadenia flower are the adhesive stigmatic lappets situated lateral to the entrance of the long slender spur (Fig. 12a-d), ready to embrace and hopefully capture any pollinaria carried on the heads of insects that visit the flowers in search of the nectar that they produce copiously within the distal half to two-thirds of the spur. Nectar secretion (and probably also resorption) is assisted by papillae that are distributed evenly across the interior epidermis of the spur (Fig. 12f-h) in every Gymnadenia species native to Britain and Ireland Bell et al., 2009;Claessens & Kleynen, 2011). The labella of all three species investigated here have a fairly uniform adaxial epidermis of domed cells bearing fine longitudinal cuticular ridges that radiate outward from the apex of each cell (Fig. 12e); these cells act collectively as a dispersed osmophore to emit the powerful fragrance (Stpiczynska, 2001). ...
Circumscriptions of both the genus Gymnadenia and the 11–27 species that it contains are highly controversial. These Eurasian terrestrial orchids are nectar-rewarding and pollinated primarily by Lepidoptera. Opinions expressed on the number of species occurring in the British Isles range from one to four, though there exists broad agreement that at least three recognizable, ecologically differentiated taxa are widespread. Here, we use a large-scale morphometric survey of these supposedly ‘cryptic’ taxa to determine whether phenotypic differentiation exists alongside their documented genotypic and ecological differentiation, seeking the most diagnostic morphological characters. Ten Gymnadenia plants were measured in each of 29 populations that encompassed the entire taxonomic range and geographic distribution of the genus within the British Isles. Results were subjected to detailed multivariate and univariate analyses, and interpreted in the context of molecular phylogenies, including a bespoke Europe-wide nrITS phylogeny that includes 17 plants sampled across Britain and Ireland. Floral micromorphology was investigated through scanning electron microscopy. Ecotypes occurring respectively in calcareous grasslands (G. conopsea s.s.), acid heaths (G. borealis) and calcareous to neutral marshes (G. densiflora) are subtly but reliably distinct, both morphologically and molecularly, though locally their morphological distinctiveness is somewhat weakened by the occurrence of infrequent populations in dune slacks and chalk downs that are intermediate in phenotype between the grassland and marsh ecotypes ('subsp. cf. friesica'). A polythetic taxonomic key emphasizes the characters and character-state ranges that are demonstrably the most diagnostic. Given that they are reliably genetically differentiable, and individuals can be distinguished with ∼85% confidence using morphological characters such as flower dimensions, depth of flower colour, and leaf number and size, we uphold our previous arguments that the three ecotypes merit species-level recognition. In the continued absence of field sequencing devices, identification is best attempted through quantitative examination of morphology focused at the population level, rejecting records of isolated plants. Despite their strong morphological similarity, genus-wide molecular data show that the British species are not each other's closest relatives. Gymnadenia borealis remains one of only three orchid species putatively endemic to the British Isles.
... Structural studies of orchids have focused on flower parts generally due to the morphological variety and unrivaled pollination strategies of flowers (Stpiczyńska, 2003;Cozzolino and Widmer, 2005;Schiestl, 2005;Bell et al., 2009;Vereecken, 2009;Anton et al., 2012;Nunes et al., 2015). Furthermore, studies about the internal and surface structure of seeds rather than fruit, symbiotic-asymbiotic germination trials or orchid-fungus relationships are seen to be more notable (Gamarra et al., 2007;Chemisquy et al., 2009;Chen et al., 2012;Gamarra et al., 2012;Tesitelová et al., 2012;Bektaş et al., 2013). ...
In this study, we have investigated the anatomy and ultrastructure of the pericarp to determine important characters of the fruits belonging to some Turkish orchidoid species, and to determine which features are related to ecological or habitat preferences. For the purpose, the samples belonging to 19 orchid taxon were collected in the Black Sea Region. SEM and light microscopy photographs were taken with the standard techniques. Variations among taxa were evaluated using various statistical methods such as correlation and discrimination analysis. Among the investigated characteristics, fruit surface ornamentation is related to habitat preferences of the species while morphometric properties of epidermal cells and structural features such as the type of crystal inclusions are important characters at the genus level.
... The presence of a spur or such structures in nectar-free species of orchids significantly increases the rate of pollination (Hodges and Arnold 1995). D. fuchsii (Druce) Soó and D. sambucina L. Soó spur have both striate ornamentation and papillae (Bell et al. 2009). The morphological and micromorphological characteristics of D. viridis and D. iberica (M. ...
This study aimed to compare the labellum and spur papillae and also the papillae types as taxonomic characters to circumscribe taxa of the genus Dactylorhiza Necker ex Nevski distributed in Anatolia (Turkey). Plant samples were collected from different regions of Anatolia, especially the Black Sea Region. Ten species were examined using light and scanning electron microscopy. The papillae and epidermis cell size of the taxa were measured and statistically compared. The papillae of the labellum were morphologically similar among the species, except for the surface striation. Spur papillae are different from the labellum papillae. Dactylorhiza characteristics such as labellum papillae shape and surface ornamentation, spur papillae shape, spur shape, and spur/ovary rate are relevant for the taxonomy of the genus.
