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Cozzolino S, Scopece G, Lussu M, Cortis P, Schiestl FP. Do floral and ecogeographic isolation allow the co-occurrence of two ecotypes of Anacamptis papilionacea (Orchidaceae)? Ecol Evol 2021; 11:9917-9931. [PMID: 34367549 PMCID: PMC8328454 DOI: 10.1002/ece3.7432] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Revised: 02/10/2021] [Accepted: 02/18/2021] [Indexed: 11/08/2022] Open
Abstract
Ecotypes are relatively frequent in flowering plants and considered central in ecological speciation as local adaptation can promote the insurgence of reproductive isolation. Without geographic isolation, gene flow usually homogenizes the allopatrically generated phenotypic and ecological divergences, unless other forms of reproductive isolation keep them separated. Here, we investigated two orchid ecotypes with marked phenotypic floral divergence that coexist in contact zones. We found that the two ecotypes show different ecological habitat preferences with one being more climatically restricted than the other. The ecotypes remain clearly morphologically differentiated both in allopatry and in sympatry and differed in diverse floral traits. Despite only slightly different flowering times, the two ecotypes achieved floral isolation thanks to different pollination strategies. We found that both ecotypes attract a wide range of insects, but the ratio of male/female attracted by the two ecotypes was significantly different, with one ecotype mainly attracts male pollinators, while the other mainly attracts female pollinators. As a potential consequence, the two ecotypes show different pollen transfer efficiency. Experimental plots with pollen staining showed a higher proportion of intra- than interecotype movements confirming floral isolation between ecotypes in sympatry while crossing experiments excluded evident postmating barriers. Even if not completely halting the interecotypes pollen flow in sympatry, such incipient switch in pollination strategy between ecotypes may represent a first step on the path toward evolution of sexual mimicry in Orchidinae.
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Affiliation(s)
| | - Giovanni Scopece
- Department of BiologyUniversity Federico II of NaplesNapoliItaly
| | - Michele Lussu
- Department of Life and Environmental SciencesUniversity of CagliariCagliariItaly
- Istituto Regionale per la Floricoltura (IRF)SanremoItaly
| | - Pierluigi Cortis
- Department of Life and Environmental SciencesUniversity of CagliariCagliariItaly
| | - Florian P. Schiestl
- Department of Systematic and Evolutionary Botany and Botanical GardensUniversity of ZurichZurichSwitzerland
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Basist G, Dyer AG, Garcia JE, Raleigh RE, Lawrie AC. Why Variation in Flower Color May Help Reproductive Success in the Endangered Australian Orchid Caladenia fulva. FRONTIERS IN PLANT SCIENCE 2021; 12:599874. [PMID: 33633758 PMCID: PMC7899986 DOI: 10.3389/fpls.2021.599874] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Accepted: 01/15/2021] [Indexed: 05/27/2023]
Abstract
Caladenia fulva G.W. Carr (Tawny Spider-orchid) is a terrestrial Australian endangered orchid confined to contiguous reserves in open woodland in Victoria, Australia. Natural recruitment is poor and no confirmed pollinator has been observed in the last 30 years. Polymorphic variation in flower color complicates plans for artificial pollination, seed collection and ex situ propagation for augmentation or re-introduction. DNA sequencing showed that there was no distinction among color variants in the nuclear ribosomal internal transcribed spacer (ITS) region and the chloroplast trnT-trnF and matK regions. Also, authentic specimens of both C. fulva and Caladenia reticulata from the reserves clustered along with these variants, suggesting free interbreeding. Artificial cross-pollination in situ and assessment of seed viability further suggested that no fertility barriers existed among color variants. Natural fruit set was 15% of the population and was proportional to numbers of the different flower colors but varied with orchid patch within the population. Color modeling on spectral data suggested that a hymenopteran pollinator could discriminate visually among color variants. The similarity in fruiting success, however, suggests that flower color polymorphism may avoid pollinator habituation to specific non-rewarding flower colors. The retention of large brightly colored flowers suggests that C. fulva has maintained attractiveness to foraging insects rather than evolving to match a scarce unreliable hymenopteran sexual pollinator. These results suggest that C. fulva should be recognized as encompassing plants with these multiple flower colors, and artificial pollination should use all variants to conserve the biodiversity of the extant population.
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Affiliation(s)
- Georgia Basist
- School of Science, RMIT University, Bundoora, VIC, Australia
| | - Adrian G. Dyer
- Bio-inspired Digital Sensing Lab, School of Media and Communication, RMIT University, Melbourne, VIC, Australia
- Department of Physiology, Monash University, Melbourne, VIC, Australia
| | - Jair E. Garcia
- Bio-inspired Digital Sensing Lab, School of Media and Communication, RMIT University, Melbourne, VIC, Australia
| | - Ruth E. Raleigh
- School of Science, RMIT University, Bundoora, VIC, Australia
- Royal Botanic Gardens Melbourne, South Yarra, VIC, Australia
| | - Ann C. Lawrie
- School of Science, RMIT University, Bundoora, VIC, Australia
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Borràs J, Cursach J. Female and male fitness of a sexually deceptive orchid with a narrow distribution area: from phenotypic traits to spatial distribution patterns. PLANT BIOLOGY (STUTTGART, GERMANY) 2021; 23:130-139. [PMID: 32959484 DOI: 10.1111/plb.13184] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Accepted: 09/09/2020] [Indexed: 06/11/2023]
Abstract
The Orchidaceae family presents one of the most extravagant pollination mechanisms: deception. While many studies on reproductive success have been performed on food-deception orchids, less have been performed on sexually deceptive orchids. Here, we focused on Ophrys balearica P. Delforge, an endemic orchid of the Balearic Islands, to study its reproductive ecology, the spatio-temporal variation of its reproductive success and the individual (floral display and geospatial position) and population parameters (patch size, shape and density) that affect its reproductive success. We performed hand-pollination experiments, along with the recording of floral display parameters and GPS position of over 1,100 individuals from seven populations in two consecutive years. We applied, for the first time, GIS tools to analyse the effects of individual's position within the population on the reproductive success. Reproductive success was measured both in male (removed pollinia) and female (fruit set) fitness. The results confirm that this species is pollinator-dependent and mostly allogamous, but also self-compatible. This species showed high values for the cumulative inbreeding depression index and high pollen limitation. Male fitness was almost equal to female fitness between years and populations, and reproductive success exhibited huge spatio-temporal variation. Although we did not find strong correlations between floral display and reproductive success, patches with low-plant density and individuals in the external portion of the population showed significantly higher plant fitness. These findings must be considered in conservation actions for endangered orchid species, especially considering that most orchids are strongly dependent on pollinators for their species' fitness.
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Affiliation(s)
- J Borràs
- Laboratory of Botany, Research Group on Plant Biology under Mediterranean Conditions, Department of Biology, University of Balearic Islands, Palma, Spain
| | - J Cursach
- Laboratory of Botany, Research Group on Plant Biology under Mediterranean Conditions, Department of Biology, University of Balearic Islands, Palma, Spain
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Baguette M, Bertrand JAM, Stevens VM, Schatz B. Why are there so many bee-orchid species? Adaptive radiation by intra-specific competition for mnesic pollinators. Biol Rev Camb Philos Soc 2020; 95:1630-1663. [PMID: 32954662 DOI: 10.1111/brv.12633] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Revised: 06/09/2020] [Accepted: 06/15/2020] [Indexed: 01/08/2023]
Abstract
Adaptive radiations occur mostly in response to environmental variation through the evolution of key innovations that allow emerging species to occupy new ecological niches. Such biological innovations may play a major role in niche divergence when emerging species are engaged in reciprocal ecological interactions. To demonstrate coevolution is a difficult task; only a few studies have confirmed coevolution as driver of speciation and diversification. Herein we review current knowledge about bee orchid (Ophrys spp.) reproductive biology. We propose that the adaptive radiation of the Mediterranean orchid genus Ophrys, comprising several hundred species, is due to coevolutionary dynamics between these plants and their pollinators. We suggest that pollination by sexual swindling used by Ophrys orchids is the main driver of this coevolution. Flowers of each Ophrys species mimic a sexually receptive female of one particular insect species, mainly bees. Male bees are first attracted by pseudo-pheromones emitted by Ophrys flowers that are similar to the sexual pheromones of their females. Males then are lured by the flower shape, colour and hairiness, and attempt to copulate with the flower, which glues pollen onto their bodies. Pollen is later transferred to the stigma of another flower of the same Ophrys species during similar copulation attempts. In contrast to rewarding pollination strategies, Ophrys pollinators appear to be parasitized. Here we propose that this apparent parasitism is in fact a coevolutionary relationship between Ophrys and their pollinators. For plants, pollination by sexual swindling could ensure pollination efficiency and specificity, and gene flow among populations. For pollinators, pollination by sexual swindling could allow habitat matching and inbreeding avoidance. Pollinators might use the pseudo-pheromones emitted by Ophrys to locate suitable habitats from a distance within complex landscapes. In small populations, male pollinators would disperse once they have memorized the local diversity of sexual pseudo-pheromone bouquets or if all Ophrys flowers are fertilized and thus repel pollinators via production of repulsive pheromones that mimic those produced by fertilized female bees. We propose the following evolutionary scenario: Ophrys radiation is driven by strong intra-specific competition among Ophrys individuals for the attraction of species-specific pollinators, which is a consequence of the high cognitive abilities of pollinators. Male bees record the pheromone signatures of kin or of previously courted partners to avoid further copulation attempts, thereby inducing strong selection on Ophrys for variation in odour bouquets emitted by individual flowers. The resulting odour bouquets could by chance correspond to pseudo-pheromones of the females of another bee species, and thus attract a new pollinator. If such pollinator shifts occur simultaneously in several indivuals, pollen exchanges might occur and initiate speciation. To reinforce the attraction of the new pollinator and secure prezygotic isolation, the following step is directional selection on flower phenotypes (shape, colour and hairiness) towards a better match with the body of the pollinator's female. Pollinator shift and the resulting prezygotic isolation is adaptive for new Ophrys species because they may benefit from competitor-free space for limited pollinators. We end our review by proritizing several critical research avenues.
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Affiliation(s)
- Michel Baguette
- Institut Systématique, Evolution, Biodiversité (ISYEB), UMR 7205 Museum National d'Histoire Naturelle, CNRS, Sorbonne Université, EPHE, Université des Antilles, F-75005, Paris, France.,Centre National de la Recherche Scientifique and Université Paul Sabatier Toulouse III, SETE Station d'Ecologie Théorique et Expérimentale, UMR 5321, F-09200, Moulis, France
| | - Joris A M Bertrand
- LGDP (Laboratoire Génome et Développement des Plantes) UMR5096, Université de Perpignan Via Domitia -CNRS, F-66860, Perpignan, France
| | - Virginie M Stevens
- Centre National de la Recherche Scientifique and Université Paul Sabatier Toulouse III, SETE Station d'Ecologie Théorique et Expérimentale, UMR 5321, F-09200, Moulis, France
| | - Bertrand Schatz
- CEFE (Centre d'Ecologie Fonctionnelle et Evolutive) UMR 5175, CNRS - Université de Montpellier - Université Paul Valéry - EPHE, 1919 Route de Mende, 34293, Montpellier, France
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Tao Z, Ren Z, Bernhardt P, Liang H, Li H, Zhao Y, Wang H, Li D. Does reproductive isolation reflect the segregation of color forms in Spiranthes sinensis (Pers.) Ames complex (Orchidaceae) in the Chinese Himalayas? Ecol Evol 2018; 8:5455-5469. [PMID: 29938065 PMCID: PMC6010815 DOI: 10.1002/ece3.4067] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Revised: 03/09/2018] [Accepted: 03/12/2018] [Indexed: 01/16/2023] Open
Abstract
Isolation between species, or taxa sharing a common lineage, depends primarily on the relative strengths of various reproductive barriers. Previous studies on reproductive isolation between orchids emphasized mechanical and ethological barriers in flowers of species showing food and/or sexual mimicry. In this study, we investigated and quantified a series of prepollination and postpollination barriers between pink and white forms of Spiranthes sinensis sl, a nectar-secreting complex. We generated ML trees based on trnS-G and matK to explore phylogenetic relationships in this species complex. Spiranthes sinensis sl segregated from some other congeners, but the white form constituted a distinct clade in relation to the pink form. The white form secreted 2-Phenylethanol as it is a single-scent compound and was pollinated almost exclusively by native, large-bodied Apis cerana and Bombus species (Apidae). Apis cerana showed a high floral constancy to this form. The scentless, pink form was pollinated primarily by smaller bees in the genera Ceratina (Apidae), and members of the family Halictidae, with infrequent visits by A. cerana and Bombus species. Fruit set and the production of large embryos following interform pollination treatments were significantly lower compared to intraform pollination results for the white form. Our results suggested that pollinator isolation, based on color and scent cues, may result in greater floral constancy in white populations when both forms are sympatric as two different, guilds of pollinators forage selectively preventing or reducing prospective gene flow. Postpollination barriers appear weaker than prepollination barriers but they also play a role in interform isolation, especially in the white form. Our findings suggest that floral color forms in S. sinensis do not represent an unbalanced polymorphism. Interpretations of the evolutionary status of these forms are discussed.
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Affiliation(s)
- Zhi‐Bin Tao
- Key Laboratory for Plant Diversity and Biogeography of East AsiaKunming Institute of BotanyChinese Academy of SciencesKunmingChina
- Kunming College of Life SciencesUniversity of Chinese Academy of SciencesKunmingChina
| | - Zong‐Xin Ren
- Key Laboratory for Plant Diversity and Biogeography of East AsiaKunming Institute of BotanyChinese Academy of SciencesKunmingChina
| | | | - Huan Liang
- Key Laboratory for Plant Diversity and Biogeography of East AsiaKunming Institute of BotanyChinese Academy of SciencesKunmingChina
- Kunming College of Life SciencesUniversity of Chinese Academy of SciencesKunmingChina
| | - Hai‐Dong Li
- Key Laboratory for Plant Diversity and Biogeography of East AsiaKunming Institute of BotanyChinese Academy of SciencesKunmingChina
| | - Yan‐Hui Zhao
- Key Laboratory for Plant Diversity and Biogeography of East AsiaKunming Institute of BotanyChinese Academy of SciencesKunmingChina
| | - Hong Wang
- Key Laboratory for Plant Diversity and Biogeography of East AsiaKunming Institute of BotanyChinese Academy of SciencesKunmingChina
| | - De‐Zhu Li
- Germplasm Bank of Wild SpeciesKunming Institute of BotanyChinese Academy of SciencesKunmingChina
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When it pays to cheat: Examining how generalized food deception increases male and female fitness in a terrestrial orchid. PLoS One 2017; 12:e0171286. [PMID: 28141838 PMCID: PMC5283728 DOI: 10.1371/journal.pone.0171286] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Accepted: 01/19/2017] [Indexed: 12/01/2022] Open
Abstract
Background Experimental manipulations of floral nectar in food deceptive species can reveal insights into the evolutionary consequences of the deceptive strategy. When coupled to pollen tracking, the effects of the deceptive pollination syndrome on both male and female reproductive success may be quantified. Attraction of pollinators in deceit-pollinated species often relies on producing a conspicuous floral display which may increase visibility to pollinators, but in-turn may increase within plant selfing. Methodology To understand the role of deception in Orchidaceae reproduction we studied Cypripedium candidum. All species of the Cypripedium genus employ a generalized food deceptive pollination strategy and have been suggested as a model system for the study of pollinator deception. We conducted a nectar addition experiment that randomly assigned the four plants closest to a transect point to receive one of four histochemical dyes. Two individuals selected for nectar addition in each of altogether 25 blocks received 2μl of 25% sucrose solution in the labellum of each flower, while two others received no artificial nectar. Number of fruits produced, fruit mass and fruit abortion were scored at the end of the four-month experiment. Results Nectar addition increased (p<0.0001) self-pollination and pollen discounting by nearly 3x, while plants not receiving nectar had greater (p<0.0001) numbers of non-self pollinia deposited and lower rates of pollen discounting. There was a non-significant (p = 0.0645) trend for deceptive plants to set more fruit, while presence of nectar did not affect pollen export. Conclusions This study demonstrates the adaptive advantages of food deception by showing a concurrent reduction in particular male and female functions when a food reward is restored to a deceptive flower. We found generalized food deception to not only decrease inbreeding depression in the system, but concurrently have no effect on pollinator attraction and fruit set when compared with rewarding flowers.
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