No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Cozzolino S, Nardella AM, Impagliazzo S, Widmer A, Lexer C. Hybridization and conservation of Mediterranean orchids: should we protect the orchid hybrids or the orchid hybrid zones? Biol Cons 129: 14-23
Abstract
Natural hybridization between plant species often occurs in disturbed habitats and it is generally considered a threat for rare and endangered species. A different situation occurs in Mediterranean food deceptive orchids, where hybridization is a common phenomenon, as a natural consequence of their unspecific pollination system.Here, we present molecular and ecological evidence from a hybrid zone between Orchis mascula and O. pauciflora in order to address the consequences of hybridization on local orchid evolution and to assess conservation priorities for hybrids and hybrid zones in orchid conservation programs.We find that, although hybrids among the two target taxa are formed relatively frequently, hybrid zones often consist of F1 individuals, whereas backcrosses and later generation hybrids appear to be either rare or absent, presumably as a consequence of post-zygotic reproductive barriers acting in these food-deceptive orchids. Experimental evidence further indicates that hybrids are less fit than the parental species in attracting pollinators and that parental taxa exhibit higher or similar fitness in sympatry compared to allopatric populations. Since introgression is not frequent as indicated by molecular analyses, fitness and phenotypic trait differences observed among sympatric and allopatric populations of the parental taxa may be a consequence of pollinator-mediated selection.Our experimental data confirm that hybridization is a natural phenomenon in food-deceptive orchids and that it does not pose a threat to their survival. Furthermore, sympatric zones provide the stage for evolutionary processes in orchids, and this peculiarity should be taken into account when devising orchid conservation strategies.
... Regarding evolutionary processes, natural hybridization is a common phenomenon and has long been suspected to be a potent evolutionary force (Li et al. 2021a, Fiorini et al. 2023. It has been suggested that a significant number of flowering plants may be of hybrid origin (Cozzolino et al. 2006). Orchid hybrids contribute to the ongoing evolutionary processes by introducing new genetic combinations and variations (Cozzolino et al. 2006, Johnson 2018, Evans et al. 2023. ...
... It has been suggested that a significant number of flowering plants may be of hybrid origin (Cozzolino et al. 2006). Orchid hybrids contribute to the ongoing evolutionary processes by introducing new genetic combinations and variations (Cozzolino et al. 2006, Johnson 2018, Evans et al. 2023. Also, orchid hybrids can play a role in speciation processes by serving as intermediates between parental species (Johnson 2018). ...
... Hybridization events can lead to the formation of new species through hybrid speciation, where hybrids become reproductively isolated from parental species and establish distinct evolutionary lineages (Fay et al. 2007, Pavarese et al. 2013, Marques et al. 2014). Hybridization is not merely a kind of ''evolutionary noise'' with little evolutionary significance but may instead sometimes play a positive role in evolution, either through hybrid speciation, or through the origin and transfer of novel adaptations (Cozzolino et al. 2006). ...
Orchids are a diverse group of plants, also manifested in their great diversity of flowers. Despite this, orchids are pollinated either through autogamy or allogamy (geitonogamy and xenogamy). Although there are some autogamous orchids, the majority are allogamous, mainly pollinated by xenogamy since they present physical or genetic barriers that prevent self-pollination. In addition, orchids are known for their capacity for interspecific pollination, which could influence fruits (metaxenia) and seeds (xenia) production. Its capacity for hybridization represents an opportunity to produce organisms tolerant to biotic or abiotic stress, in addition to exhibiting new shapes, colors and fragrances; this would be important in horticulture, where the proper selection of parents provides those advantages to the descendant hybrids. This review addresses the characteristics of each type of reproduction systems in orchids, as well as their advantages and disadvantages. At the same time, the study of the induction effect of metaxenia and xenia in this family is proposed. Finally, the production of orchid hybrids is contextualized and the opportunities of this approach in the near future.
... Interspecific gene flow has been typically seen as a risk in conserving biodiversity, especially because endangered species may come in contact and hybridize with more common and widespread taxa (Cozzolino et al., 2006). Accordingly, current conservation policies tend to disregard hybrids, hybrid zones and hybridizing species. ...
... However, protection is generally denied for hybrids in conservation policies (Jackiw et al., 2015;von Holdt et al., 2018). The rigidity of the biological species concept (Marques et al., 2018), the extinction or displacement of parental species -and the consequently threat in the case of endangered species-, or the relation of hybrids with human disturbed habitats and invasive species (Cozzolino et al., 2006) could represent some of the causes why natural hybridization has been considered deleterious. In contrast, V. × gundisalvi occurs in natural habitats through homoploid hybridization and does not displace any of the parental taxa: V. tenuifolia subsp. ...
... We are facing a scenario of climatic change and biodiversity loss with little resources for conservation. Thus, conservation priorities should focus mostly on protecting areas where we can still act to preserve ecological and evolutionary processes such as hybridization (Cozzolino et al., 2006). Conservation strategies involving practitioners have proven to be formulas of great success (e.g., initiatives as "Adopta una planta"; http://www.liferesecom.ipe.csic.es/index2. ...
Hybridization is an important mechanism in plant evolution, which contributes to the adaptability and biological diversity of species in fundamental ways. Based on morphological data, Veronica × gundisalvi Sennen (Veronica orsiniana × V. tenuifolia subsp. tenuifolia) is an Iberian endemic taxon of presumably polytopic hybrid origin restricted to five localities in Catalonia, where the putative parental species grow in sympatry. In this study, species distribution models were developed for the putative parental species to seek potential new localities where active hybridization could be taking place. As a result, a new location of this nothotaxon in Zaragoza is provided, along with a chromosome count and ploidy level estimations. The data presented here further support Veronica × gundisalvi as a homoploid hybrid taxon that occurs in non-altered habitats. In contrast to the traditional view of hybridization as deleterious for the conservation of biodiversity, it does not always represent a problem in this regard. Hybridization is a complex evolutionary force that requires case-specific evaluation. Given that biodiversity loss is one of the main contemporary challenges, it is important to consider the creative nature of hybridization, a widespread evolutionary mechanism able to produce novel diversity.
... The evolutionary processes that promote diversification have been increasingly recognised as important elements in biodiversity conservation (Smith et al. 1993;Moritz 1994;Crandall et al. 2000;Stockwell et al. 2003;Ellstrand et al. 2010). As a result of its prominent evolutionary role in plants, hybridisation has become a topic of particular interest in this respect (Allendorf et al. 2001;Cozzolino et al. 2006;Ellstrand et al. 2010;Thompson et al. 2010;Stronen & Paquet 2013;Jackiw et al. 2015). First, it is critical here to distinguish between hybrids that have a natural or anthropogenic origin because hybridisation among introduced and native species can cause genetic pollution of the latter (Allendorf et al. 2001;Jackiw et al. 2015). ...
... Natural hybridisation can also be a serious threat to rare and endangered species because of the possibility of extensive genetic introgression (Rieseberg & Gerber 1995;Levin et al. 1996;Mameli et al. 2014). However natural hybridisation is beneficial when it increases genetic diversity, fitness and adaptive potential (Stebbins 1950;Cozzolino et al. 2006;Abbott et al. 2010; Thompson et al. 2010). Hence, the significance of hybridisation for conservation issues may vary and it is critical to distinguish cases of hybridisation that have given rise to the evolution of new species from examples of contemporary and potentially on-going hybridisation that represent a source of new diversity and are potentially incipient species (Harrison 1993;Cozzolino et al. 2006; Thompson et al. 2010;Mameli et al. 2014). ...
... However natural hybridisation is beneficial when it increases genetic diversity, fitness and adaptive potential (Stebbins 1950;Cozzolino et al. 2006;Abbott et al. 2010; Thompson et al. 2010). Hence, the significance of hybridisation for conservation issues may vary and it is critical to distinguish cases of hybridisation that have given rise to the evolution of new species from examples of contemporary and potentially on-going hybridisation that represent a source of new diversity and are potentially incipient species (Harrison 1993;Cozzolino et al. 2006; Thompson et al. 2010;Mameli et al. 2014). ...
Hybridisation plays a prominent role in plant evolution due to its influence on genetic diversity, fitness and adaptive potential. We identify a case of on‐going hybrid evolution of floral phenotypes in disjunct populations of Cyclamen balearicum and C. repandum subsp. repandum on Corsica and Sardinia.
Hybrid populations on the two islands contain similar patterns of variation in flower colour and size but are probably at different stages in the evolutionary process of hybridisation, and differences in the frequency of floral types and flower size suggest hybrid vigour that may contribute to the dynamics and maintenance of hybrid forms.
In a review of cases of hybridisation in Mediterranean plants we found an equivalent number of cases for the contemporary occurrence of mixed hybrid populations, as there are cases of homoploid hybrid species differentiation.
We argue for the development of a conservation strategy for Mediterranean plants that integrates the need to protect not just pure endemic species (some of hybrid origin) but also mixed populations where adaptive variation and new species are evolving due to contemporary hybridisation.
... Recent investigations in a range of European ( Orchis L., Anacamptis Rich., Dactylorhiza Neck. ex Nevski) and Neotropical ( Epidendrum L.) food-deceptive orchids have shown that reproductive barriers are far from strict and that hybridization may frequently occur (e.g., Cozzolino et al., 2006 ;Moccia et al., 2007 ;Pellegrino et al., 2010 ;Pinheiro et al., 2010 ;De Hert et al., 2011Jacquemyn et al., 2012a , b ;Moraes et al., 2013 ;Scopece et al., 2013 ;Marques et al., 2014 ). Comparative analyses of premating and postmating barriers have revealed that, in contrast to sexually deceptive species, premating isolation barriers in food-deceptive species are mostly weak ( Scopece et al., 2007 ;Marques et al., 2014 ). ...
... This suggests that the evolution of intrinsic postzygotic isolation strongly contributes to maintaining species boundaries among food-deceptive orchids ( Scopece et al., 2008( Scopece et al., , 2013 and that neither introgression nor the formation of hybrid swarms represents a major threat to the longterm survival of most of these species. However, the possibility that hybridization in orchids reduces the fi tness of the parental species has only rarely been considered (but see Cozzolino et al., 2006 ). ...
... Interspecifi c mating between pure parental plants may have contributed to the lower seed viability in the sympatric population, although the reductions in seed viability appeared to be lower than those following backcrossings with putative hybrids. Th ese results are in contrast with fi ndings of Cozzolino et al. (2006) , who showed that parental species had higher or similar fi tness in sympatry than in allopatric populations of two Orchis species: Orchis mascula (L.) L. and O. paucifl ora Fisch. ex Lindl. ...
Premise of the study:
Hybridization may pose severe threats to the long-term survival of the parental taxa through introgression and the formation of hybrid swarms. However, when the resulting hybrids show strong male and female sterility, backcrossing and introgression are unlikely to occur, but the parental species may suffer from reduced male and female fitness.
Methods:
We assessed the impact of hybridization on the long-term persistence of two food-deceptive orchids in the genus Dactylorhiza (the common Dactylorhiza maculata and the rare D. sphagnicola). The extent of hybridization was investigated using both molecular markers and morphometric measurements. To determine the strength of postmating reproductive isolation, hand pollinations were conducted between pure and hybrid individuals. Finally, fruit set and seed viability of open-pollinated plants were determined in sympatric and allopatric populations to investigate the impact of hybridization on the reproductive output of the pure parental species.
Key results:
Our results showed that postmating reproductive isolation was weak and that hybridization occurred frequently within the studied sympatric population. Although hybrids were characterized by very low female fitness, mainly because of strongly reduced seed viability, backcrossing appeared to occur and was asymmetric toward the rare D. sphagnicola. Fruit set and seed viability of open-pollinated plants were also significantly lower in the sympatric population than in the allopatric populations, indicating that hybridization and ongoing introgression incurred fitness costs in the pure parental species.
Conclusions:
Overall, our results suggest that extensive hybridization can affect the long-term viability of the parental species through the combined effect of introgression following interspecific hybrid fertilization and reduced fitness of the parental species.
... Among many biases, the idea of hybridization as a threat was found to be quite subjective in most of the assessments made, since there were no specific guidelines for quantifying the degree of threat deriving from hybridization [11]. In the opposite direction, possible benefits for the conservation of species deriving from hybridization are usually not considered [12,13]. Thus, determining the consequences of hybridization-either positive or negative-is crucial to understand the impacts that hybridization might have, and to tackle the causes of biodiversity loss. ...
... Independently of the outcomes, hybridization appears to be a widespread process in plants, since about 25% of the known species hybridize naturally [14]. The number of reported hybrids is considerably high in well-studied temperate regions [15], with many specific studies detecting the complex consequences of hybridization, introgression, and hybrid speciation, as well as the challenges beyond hybridization [13,[16][17][18][19]. Other studies evaluate the power of the analytic methods to detect the significance of the process itself [20]. ...
Hybridization and introgression are complex evolutionary mechanisms that can increase species diversity and lead to speciation, but may also lead to species extinction. In this study, we tested the presence and genetic consequences of hybridization between the rare and Ecuadorian endemic O. loxensis van der Werff and the widespread O. infrafoveolata van der Werff (Lauraceae). Phenotypically, some trees are difficult to identify, and we expect that some might in fact be cryptic hybrids. Thus, we developed nuclear microsatellites to assess the existence of hybrids, as well as the patterns of genetic diversity and population structure in allopatric and sympatric populations. The results revealed high levels of genetic diversity, even in the rare O. loxensis, being usually significantly higher in sympatric than in allopatric populations. The Bayesian assignment of individuals into different genetic classes revealed a complex scenario with different hybrid generations occurring in all sympatric populations, but also in allopatric ones. The absence of some backcrossed hybrids suggests the existence of asymmetric gene flow, and that some hybrids might be more fitted than others might. The existence of current and past interspecific gene flow also explains the blurring of species boundaries in these species and could be linked to the high rates of species found in Ocotea.
... Natural hybridization within the plant kingdom is a double-edged evolutionary force. Hybridization may facilitate adaptive allele sharing or break apart coadapted gene groups, just as it may generate stable hybrid populations or genetically erode rare parent species [12,69]. We documented contemporary hybridization between the fringed orchid species P. ciliaris, P. blephariglottis, and P. cristata with genomic and morphological approaches. ...
... If the hybrids have an adaptive advantage over their parent species, they might evolve into a stable population with the potential to generate a separate species. Still, widespread hybridization can result in genetic erosion of endangered or locally endangered parent species [12,69]. The hybrid P. x canbyi is confined to sympatric sites, and we do not see any clear evidence of genetic erosion in P. cristata or P. blephariglottis. ...
Natural hybridization between closely related species in sympatry is an evolutionary process that is common in orchids. Once seen as a threat to parent species, interspecific genetic change is increasingly viewed as a source of novel variation in some ecological contexts. Terrestrial fringed orchids in the genus Platanthera contain several clades with high genetic compatibility among species and many putative hybrids. We used biallelic SNPs generated with 3RAD sequencing to study the hybrid complex formed from the parent species P. blephariglottis, P. ciliaris, and P. cristata with high resolution. The genetic structure and phylogenetic relationship of the hybrid complex revealed site-dependent gene flow between species. We documented extensive hybridization and cryptic hybrids in sympatric sites. Interspecific genetic exchange is particularly common between P. blephariglottis and P. ciliaris, with cryptic hybrids among putative P. ciliaris samples being more common than parental assignments in sympatric sites. Hybridization across the triad species complex can reticulate lineages and introduce adaptive alleles. Conversely, it can reduce diversification rates and introduce maladaptive alleles. Investigation into whether anthropogenic forces are eroding species boundaries, particularly the permeable P. blephariglottis and P. ciliaris boundary, is appropriate for conservation efforts.
... Hybridization among plant species is common in the wild and is thought to be a driving force in evolution [1,2]. Indeed, plant speciation through hybridization (such as allopolyploidy or homoploid hybrid speciation) is widespread in the plant kingdom [3][4][5]. However, hybridization can also lead to introgression and the loss of unique genetic identities within populations [6,7]. ...
... It is important to note that fruit development in orchids is a direct result of pollination and is independent of later fertilization since pollen deposition causes ovary enlargement. [90], Consequently, estimates of fruit production can serve as indirect estimates of plant pollination success [4]. We might be careful, therefore, in considering the role of the hybrid in the distribution of the rare O. patens. ...
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.
... Rates and outcomes of hybridization vary across populations and communities, and the causes of this variation are not always fully understood . The outcome of hybridization can impact community structure and depends on the frequency of inter-specific mating, compatibility of parental species, and the fitness of hybrids relative to their parents (Cozzolino et al. 2006;Vilà et al. 2000). ...
... Interactions with the environment and the nature of the genetic control of traits influence the expression of those traits in hybrid offspring Wu and Campbell 2005). Backcrossing between hybrid offspring and parental taxa (or other hybrids) may allow transfer of certain traits via a "genetic bridge" (Cozzolino et al. 2006). This transfer of genetic material however, may not be equal from both parental taxa The functional floral morphology in relation to effective pollination has been studied in relatively few (six to my knowledge) of the approximately 45 Cypripedium species (Bänziger et al. 2005Edens-Meier et al. 2011;. ...
I investigated how orchid biology, floral morphology, and diversity of surrounding floral and pollinator communities affected reproductive success and hybridization of Cypripedium candidum and C. parviflorum. Floral dimensions, including pollinator exit routes were smallest in C. candidum, largest in C. parviflorum, with hybrids intermediate and overlapping with both. This pattern was mirrored in the number of insect visitors, fruit set, and seed set. Exit route size seemed to restrict potential pollinators to a subset of visiting insects, which is consistent with reports from other rewardless orchids. Overlap among orchid taxa in morphology, pollinators, flowering phenology, and spatial distribution, may affect the frequency and direction of pollen transfer and hybridization. The composition and abundance of co-flowering rewarding plants seems to be important for maintaining pollinators in orchid populations.
... It is represented in Europe by about 600 species and subspecies (Kreutz 2004), all of them terrestrial and mainly tied to open habitats as dry meadows and, less frequently, to woody habitats or wetlands. They are considered bioindicators ( Bianco 2012) and especially indicators of stability in the ecosystems (Cozzolino et al. 2006, Swarts & Dixon 2009, with a high rate of threatened species (Cribb et al. 2003). On the basis of the threats affecting the seminatural habitats richest in orchids (Calevo et al. 2018) the usefulness of marginal surrogate habitats (e.g. ...
... È rappresentata in Europa da circa 600 specie e sottospecie (Kreutz 2004), tutte terrestri e principalmente legate ad habitat aperti come prati secchi o anche ambienti boschivi o zone umide. Sono considerati bioindicatori (Bianco 2012) e in particolare indicatori di stabilità negli ecosistemi (Cozzolino et al., 2006, Swarts & Dixon 2009), con un alto tasso di specie minacciate (Cribb et al. 2003). Sullo sfondo delle minacce che colpiscono gli habitat seminaturali più ricchi di orchidee (Calevo et al. 2018) l'utilità degli habitat marginali sostitutivi (ad esempio i bordi stradali) come rifugi per le specie di prati che agiscono come apofite è stata discussa in diversi contributi (Rossi & Lippolis 1984, Rossi 1989, Adamovski 2006, Auestad et al. 2011, Fekete et al. 2017). ...
Archaeological sites can host a rich flora encompassing plant species of conservation interest as the orchids. A study was conducted in 2018 by means of floristic surveys in 7 archaeological areas in Northern Campania aiming at assessing the presence and size of populations of orchids, their conservation status and to provide information to the sites administrations about managing practices compatible with the conservation of the native flora. The study wishes to represent a case-study on the conservation of native orchids in marginal areas and specifically in the archaeological sites. In 6 out of 7 studied areas 7 species and 2 hybrids were recorded confirming the suitability of such areas for the conservation of the orchid flora and to act as refugia areas in urbanized or agricultural settings.
Riassunto: le aree archeologiche possono ospitare una ricca flora comprendente specie vegetali di interesse conservazionistico, come le orchidee. Uno studio è stato condotto nel 2018 attraverso rilevamenti in 7 aree archeologiche della Campania settentrionale al fine di valutare la consistenza delle popolazioni delle specie presenti, il loro stato di conservazione e fornire indicazioni agli enti gestori affinché gli interventi di manutenzione siano compatibili con il mantenimento delle orchidee. Tale ricerca vuole rappresentare un caso studio sulla conservazione delle orchidee nelle aree marginali, e in particolare nelle aree archeologi-che. In 6 delle 7 aree oggetto di ricerca sono state censite 7 specie e 2 ibridi, attestando l'idoneità di tali aree a conservare una flora orchidologica e a svolgere il ruolo di aree rifugio in contesti urbanizzati o agricoli. Parole chiave: conservazione orchidee, POSA (Progetto per la conservazione delle Orchidee Spontanee italiane in Aree marginali pubbliche), siti archeologici, provincia di Caserta (Campania settentrionale).
... This wide distribution also holds true for Chilean orchids, with orchid individuals growing from the Atacama Desert to southern Patagonia (Novoa et al. 2015). However, as reported for several orchids, most Chilean species are under constant threat because of several man-made ecosystem alterations such as deforestation, due to logging, fire, road construction and the expansion of cities, forest plantations and agriculture, and over-collection for the ornamental, medicinal, and food plant industries (Cozzolino et al. 2006;Gale et al. 2018). Worldwide, orchid populations are under constant threat because of climate change, segregation of orchid populations mainly to protected areas, abundance of compatible mycorrhizal fungi, and the economic potential that several orchids have (Schödelbauerová et al. 2009;Kottke et al. 2010;Waud et al. 2016b). ...
... Nowadays, conservation of flora is a worldwide problem, mainly due to alterations in natural ecosystems (McCarty 2001;Robbirt et al. 2011). This is the case of orchids, which undergo crucial reproduction steps in their life cycle and are often related to the specific interactions with their mycorrhizal fungi (Cozzolino et al. 2006;Egidi et al. 2018). There are many constraints to orchid development and conservation, and these are often related to human-induced ecosystem alteration as well as depredation (animals for food and humans for ornamental plants and urbanization) (Kottke et al. 2010;Herrera et al. 2017). ...
In order to confront the constant decline in global biological diversity, amelioration strategies are needed for threatened species to design reintroduction policies, particularly in plants with critical reproduction steps, such as orchids. Orchids are part of a highly diverse plant family, with several species under imminent extinction risk. This is the case of Chilean Orchidaceae, which has shown a constant decay in their populations due to an increase in the alteration processes of their natural distribution habitats. Successful orchid reintroductions require a full understanding of orchid mycorrhizal fungi and their dynamic according to different developmental stages and environmental conditions because orchid seeds need mycorrhizal fungi to obtain nutritional compounds at early developmental stages. This article performed a critical literature review of the ecological studies conducted on Chilean orchids and their relationships with mycorrhizal fungi in order to focus on the best scientific approach to achieve successful restoration programs involving orchid seeds and compatible mycorrhizal fungi.
... In particular, we estimated the strength and direction of natural selection over three consecutive years in a sympatric population of these two species with the aim of specifically understanding whether, in the same population, pollinator-mediated selection shows a concordant pattern over different years. We used two orchid species with similar flower morphology and a common set of pollinators (Van Der Cingel, 1995;Cozzolino et al., 2006;Nilsson, 2008;Valterovà et al., 2007) as replicates to increase the power of our conclusions for Mediterranean food-deceptive orchids. ...
... The two species are self compatible but non autogamous and rely on generalised food-deception for pollinator attraction (Van Der Cingel, 1995). Hymenopterans are the most common pollinators of these two species (specifically Bombus sp., but also species of the genus Psithyrus, Eucera, Andrena, Osmia, Anthophora), and reproductive success is severely pollen-limited (e.g.,Cozzolino et al., 2006). Clonal propagation is extremely rare in both species.). ...
Nectarless flowers that deceive pollinators offer an opportunity to study asymmetric plant-insect interactions. Orchids are a widely used model for studying these interactions because they encompass several thousand species adopting deceptive pollination systems. High levels of intra-specific phenotypic variation have been reported in deceptive orchids, suggesting a reduced consistency of pollinator-mediated selection on their floral traits. Nevertheless, several studies report on widespread directional selection mediated by pollinators even in these deceptive orchids. In this study we test the hypothesis that the observed selection can fluctuate across years in strength and direction thus likely contributing to the phenotypic variability of this orchid group. We performed a three-year study estimating selection differentials and selection gradients for nine phenotypic traits involved in insect attraction in two Mediterranean orchid species, namely Orchis mascula and O. pauciflora , both relying on a well-described food-deceptive pollination strategy. We found weak directional selection and marginally significant selection gradients in the two investigated species with significant intra-specific differences in selection differentials across years. Our data do not link this variation with a specific environmental cause, but our results suggest that pollinator-mediated selection in food-deceptive orchids can change in strength and in direction over time. In perennial plants, such as orchids, different selection differentials in the same populations in different flowering seasons can contribute to the maintenance of phenotypic variation often reported in deceptive orchids.
... There are some confirmed natural hybrid zones between orchid species that were predicted from morphology and further investigated with molecular tools (e.g. Cozzolino et al., 2006; Bateman et al., 2008; Pinheiro et al., 2010 Pinheiro et al., , 2015 Marques et al., 2014). However, not all morphological variation can be attributed to hybridization between taxa, and can alternatively be related to genetic drift or disruptive selection (Ackerman, Morales & Tremblay, 2011). ...
... In Orchidaceae, many papers report hybrids presenting intermediate morphological features (e.g. Caputo et al., 1997; Nielsen, 2000; Cozzolino et al., 2006; Moccia et al., 2007), including the genus Cattleya (Silva, 2008), but other studies illustrate the lack of consistency of morphology in identifying hybrids (e.g. Wallace, 2006; St ahlberg & Hedr en, 2009; De Hert et al., 2011). ...
... There are some confirmed natural hybrid zones between orchid species that were predicted from morphology and further investigated with molecular tools (e.g. Cozzolino et al., 2006;Bateman et al., 2008;Pinheiro et al., 2010Pinheiro et al., , 2015Marques et al., 2014). However, not all morphological variation can be attributed to hybridization between taxa, and can alternatively be related to genetic drift or disruptive selection (Ackerman, Morales & Tremblay, 2011). ...
... In Orchidaceae, many papers report hybrids presenting intermediate morphological features (e.g. Caputo et al., 1997;Nielsen, 2000;Cozzolino et al., 2006;Moccia et al., 2007), including the genus Cattleya (Silva, 2008), but other studies illustrate the lack of consistency of morphology in identifying hybrids (e.g. Wallace, 2006;St ahlberg & Hedr en, 2009;De Hert et al., 2011). ...
Cattleya coccinea and C. brevipedunculata (Orchidaceae) are closely related species distinguished primarily bygeographical distribution, vegetative morphology and flowering period. Both species inhabit high-elevationregions in south-eastern Brazil, but are traditionally associated with different habitats, located in cloudy forestsand campos rupestres (rocky fields), respectively. We used morphometrics and genetic variation of microsatellitemarkers to test the occurrence of a hybrid zone between these species located in Parque Estadual do Ibitipoca(PEI), Brazil. Morphological data reveal a continuum of variation between the putative taxa, influenced mainlyby characters of leaf, pseudobulb and peduncle. However, genetic data do not support the occurrence ofhybridization and introgression in PEI, showing that it is a pure population of C. brevipedunculata. Differencesin vegetative characters among individuals from cloudy forests and campos rupestres suggest that morphologicalvariation may be related to phenotypic plasticity in response to environmental light fluctuations, an unknownsituation for this species. These results highlight the inconsistency of morphology for the identification of hybridsand the role of vegetative characters as a possible complicating factor for the taxonomy of these species, as theyare subject to environmental influence. © 2016 The Linnean Society of London, Botanical Journal of the LinneanSociety, 2016
... Captive breeding of C. rhombifer to conserve their "genetic integrity" and prevent increased hybridization European orchids (Orchis mascula) and (Orchis pauciflora) Cozzolino et al. (2006) The role natural hybridization plays in speciation and local genetic adaptation Maintain existing hybrid zones Red wolves (Canis rufus) and coyotes (Canis latrans) Gese et al. (2015) and Bohling and Waits (2015) Hybridization occurs at an increased rate because of human activity, which makes it a problem for conservation of C. rufus Removal, killing, and sterilization of coyotes and at least some hybrid individuals to maintain the relative integrity and persistence of C. rufus Fishhook cacti (Sclerocactus glaucus and Sclerocactus parviflorus) Schwabe et al. (2015) Hybridization between the species is acceptable so long as the rates do not increase; maintain distinct northern and southern populations of S. glaucus by preventing human-mediated movement ...
Hybridization by introgression (“hybridization”) is a complex topic in conservation. Many conservation decision‐makers are concerned about hybridization by introgression because it may threaten species persistence or local phenotypes, among other potential long‐term problems. While attitudes have changed towards hybridization as a conservation threat, there are still concerns about hybridization as a problem, particularly if the hybridization was anthropogenically mediated. I propose that these concerns are overblown and that it is misguided to focus on whether hybridization is unintentionally human‐mediated. I argue that practitioners should still consider the effects of hybridization on conservation, but the reasons should concern the long‐term environmental consequences, such as ecological function and social and cultural that hybridization has, rather than whether humans “caused” the hybrid. I propose a series of steps to think differently about these cases.
... Only two specimens were observed at the time as Orchis × beyrichii, but as both parent species are abundant in the area, hybrid individuals are probably present in larger quantities as described by Zadravec et al. (2015) where 2/3 of the population at Krč is assumed to be of hybrid origin. Although this taxon is sometimes hard to distinguish from the parental species due to their polymorphism, the question of the back crossing and 'purity' of both parental species populations arises, but Cozzolino et al. (2006) ...
Four hybrid taxa, previously rarely, or now for the first time recorded in Croatia, observed during the spring of 2020 and 2022 on Mt. Papuk, are presented. A hybrid of Primula vulgaris Huds. and P. veris L. called P. × polyantha Mill. is known as an ornamental plant, which comes in a whole palette of colors, but the occurrence of spontaneous hybrids that occur in nature in Croatia has been discussed in print only once, by Degen in 1937. Ophrys × hybrida Pokorny ex Rchb. f. is a cross between O. sphegodes Mill.and O. insectifera L., and it has never previously been recorded in Croatia. Orchis × beyrichii (Rchb. f.) A. Kern. and O. × angusticruris Franch are rarely recorded hybrids in which O. simia Lam. participates, the first by crossing with the species O. militaris L., and the second with O. purpurea Huds.
... As interpreted by Hewitt (1988), hybrid zones are 'natural laboratories for evolutionary studies' as they provide experimental areas in which to study factors shaping gene flow between divergent lineages (Andújar et al., 2014;Dinis et al., 2019;Dufresnes et al., 2020) and the nature of genetic barriers. In this sense, the narrow region of Campo de Dalías, where lineage C2 occurs, merits special conservation status for preserving both historical and current evolutionary processes (Cozzolino et al., 2006;Evans et al., 2012). It seems particularly necessary to protect the Sierra de la Con- This study is only a token of the massive diversity loss faced by one of the most endemic arthropod-rich areas in Europe (Sanchez Piñero, 2006). ...
Large-scale agricultural and tourism development are the main threats to biodiversity in south-eastern Spain. Species with low dispersal abilities, such as some endemic insects from this region, are particularly vulnerable to fragmentation and loss of genetic and morphological diversity. Here, we studied the current and future threat of climate and land-use change on the intraspecific diversity of one such group of endemics, the giant blister beetles of the Berberomeloe insignis species group.
Using a phylogeographic approach and morphometrics, we identified intraspecific variation within the B. insignis species group. These data were coupled with ecological niche modelling (ENM) to determine the effect of agricultural and climate change on the connectivity across phylogroups.
We identified a marked geographic structure within B. insignis, with the time to the most recent common ancestor (TMRCA) of the two main mtDNA clades dating back to 2.1 Ma. Cyto-nuclear discordances found across parapatric populations suggest past events of genetic introgression. B. insignis presents a head pattern that is geographically structured and mostly congruent with the four mitochondrial lineages. In contrast, diversification within Berberomeloe tenebrosus is more recent, dating back to less than 1 Ma. Future ENMs highlight the role of mountains as potential refugia under a climate warming scenario but predict extinctions in the lowlands.
Based on our analyses, two lineages of B. insignis are threatened and should be urgently considered as independent conservation units, and their current geographic distribution areas protected to conserve, at the very least, a portion of the species' evolutionary heritage.
... Due to frequent hybridization and introgression, delineating taxonomic boundaries of orchids can be very difficult [11,12]. The resulting uncertainties in the taxonomy and conservation status of orchids can largely hamper effective conservation strategy-making. ...
Orchidaceae is one of the largest, most diverse families in angiosperms with significant ecological and economical values. Orchids have long fascinated scientists by their complex life histories, exquisite floral morphology and pollination syndromes that exhibit exclusive specializations than any other plants on earth. These intrinsic factors together with human influences also make it a keystone group in biodiversity conservation. The advent of sequencing technologies and transgenic techniques represents a quantum leap in orchid research, enabling molecular approaches to be employed to resolve the historically interesting puzzles in orchid basic and applied biology. To date, 15 different orchid genomes covering four subfamilies (Apostasioideae, Vanilloideae, Epidendroideae and Orchidoideae) have been released. These genome projects have given rise to massive data that greatly empowers the studies pertaining to key innovations and evolutionary mechanisms for the breadth of orchid species. The extensive exploration of transcriptomics, comparative genomics, and recent advances in gene engineering have linked important traits of orchids with a multiplicity of gene families and their regulating networks, providing great potential for genetic enhancement and improvement. In this review, we summarize the progress and achievement in fundamental research and industrialized application of orchids with a particular focus on molecular tools, and make future prospects of orchid molecular breeding and post-genomic research, providing a comprehensive assemblage of start-of-art knowledge in orchid research and industrialization.
... Due to frequent hybridization and introgression, delineating taxonomic boundaries of orchids can be very difficult [11,12]. The resulting uncertainties in the taxonomy and conservation status of orchids can largely hamper effective conservation strategy-making. ...
Orchidaceae is one of the largest, most diverse families in angiosperms with significant ecological and economical values. Orchids have long fascinated scientists by their complex life histories, exquisite floral morphology and pollination syndromes that exhibit exclusive specializations than any other plants on earth. These intrinsic factors together with human influences also make it a keystone group in biodiversity conservation. The advent of sequencing technologies and transgenic techniques represents a quantum leap in orchid research, enabling molecular approaches to be employed to resolve the historically interesting puzzles in orchid basic and applied biology. To date, 15 different orchid genomes covering four subfamilies (Apostasioideae, Vanilloideae, Epidendroideae and Orchidoideae) have been released. These genome projects have given rise to massive data that greatly empowers the studies pertaining to key innovations and evolutionary mechanisms for the breadth of orchid species. The extensive exploration of transcriptomics, comparative genomics, and recent advances in gene engineering have linked important traits of orchids with a multiplicity of gene families and their regulating networks, providing great potential for genetic enhancement and improvement. In this review, we summarize the progress and achievement in fundamental research and industrialized application of orchids with a particular focus on molecular tools, and make future prospects of orchid molecular breeding and post-genomic research, providing a comprehensive assemblage of start-of-art knowledge in orchid research and industrialization.
... The orchid-pollinator relationship shows only 67% of 456 orchid species to have known pollinators, thereby making pollinator specificity act as the main mechanism of pre-mating reproductive isolation for orchids (Cozzolino et al. 2006). Another fascinating aspect of orchid biology is their dependence on mycorrhizal fungi for symbiotic germination (Rasmussen 1995;Sathiyadash et al. 2020). ...
This edited book is focusing on the novel and innovative procedures in tissue culture for large-scale production of plantation and horticulture crops. It is bringing out a comprehensive collection of information on commercial-scale tissue culture with the objective of producing high-quality, disease-free and uniform planting material. Developing low-cost commercial tissue culture can be one of the best possible ways to attain the goal of sustainable agriculture. Tissue culture provides a means for rapid clonal propagation of desired cultivars, and a mechanism for somatic hybridization and in vitro selection of novel genotypes. The application of plant tissue culture technology in horticulture and plantation crops provides an efficient method to improve the quality and nutrition of the crops.
This book includes a description of highly efficient, low cost in vitro regeneration protocols of important plantation and horticulture crops with a detailed guideline to establish a commercial plant tissue culture facility including certification, packaging and transportation of plantlets. The book discusses somatic embryogenesis, virus elimination, genetic transformation, protoplast fusion, haploid production, coculture of endophytic fungi, effects of light and ionizing radiation as well as the application of bioreactors.
This book is useful for a wide range of readers such as, academicians, students, research scientists, horticulturists, agriculturists, industrial entrepreneurs, and agro-industry employees.
... The orchid-pollinator relationship shows only 67% of 456 orchid species to have known pollinators, thereby making pollinator specificity act as the main mechanism of pre-mating reproductive isolation for orchids (Cozzolino et al. 2006). Another fascinating aspect of orchid biology is their dependence on mycorrhizal fungi for symbiotic germination (Rasmussen 1995;Sathiyadash et al. 2020). ...
Explant preference is a key factor for efficient and sustainable plant propagation under in vitro conditions. Plant genotype and structure must be well observed and identified for the best explant which may differ in the axillary bud breakings using terminal buds on stems located above ground or specialized/underground stems such as bulbs scales, base plates of corms, and the shoot tips of suckers. Since plant factory systems are aimed at uniform and cost-effective propagation systems, determination of explant type and culture conditions are the most critical factors for the establishment of shoot multiplication rate. In this chapter, several horticulture plants including house plants (Monstera, Philodendron, Begonia, etc.), and fruit trees (Aronia, banana, walnut, etc.) used in commercial-scale production in plant factories were investigated for the understanding of the nature of explants as per culture conditions. This phenomenon is also highly correlated with effective surface sterilization. Since plant factories rely on an automation system for particular crops, replenishment of starting material in each cloning cycle prevents the emergence of undesirable traits due to the somaclonal variations. This study reports a comparative and in situ analysis of explant choice for the scalable vitro-plant productions.
... Our finding was also important in horticultural applications. Previous studies have shown that crosses between orchids with different numbers of flowers, but similar peduncle diameters, can produce hybrids with intermediate flower numbers such as Orchis pauciflora and O. mascula (Cozzolino et al., 2006) or Anacamptis × albuferensis (Bateman and Hollingsworth, 2004). In contrast, crosses between orchids with similar flower numbers but different peduncle diameters produce offspring with thicker peduncle diameters and more flowers than their parentals (Yan et al., 2017). ...
In flowering plants, inflorescence characteristics influence both seed set and pollen contribution, while inflorescence and peduncle size can be correlated with biomass allocation to reproductive organs. Peduncles also play a role in water and nutrient supply of flowers, and mechanical support. However, it is currently unclear whether inflorescence size is correlated with peduncle size. Here, we tested whether orchids with large diameter peduncles bear more and larger flowers than those with smaller peduncles by analyzing 10 traits of inflorescence, flower, and leaf in 26 species. Peduncle diameters were positively correlated with inflorescence length and total floral area, indicating that species with larger peduncles tended to have larger inflorescences and larger flowers. We also found strongly positive correlation between inflorescence length and leaf area, and between total floral area and total leaf area, which suggested that reproductive organs may be allometrically coordinated with vegetative organs. However, neither flower number nor floral dry mass per unit area were correlated with leaf number or leaf dry mass per unit area, implying that the function between leaf and flower was uncoupled. Our findings provided a new insight for understanding the evolution of orchids, and for horticulturalists interested in improving floral and inflorescence traits in orchids.
... When different species grow together and flower at the same time, species boundaries can be maintained by attracting different pollinators or by post-zygotic reproductive barriers (Cozzolino et al., 2006). These four Orchis species have the same number of chromosomes (2n = 42) Kretzschmar et al., 2007) and have overlapping phenology, pollinator communities, and habitat preferences Kretzschmar et al., 2007;Schatz et al., 2020). ...
Premise:
The genetic structure of hybrid zones provides insight into the potential for gene flow to occur between plant taxa. Four closely related European orchid species (Orchis anthropophora, O. militaris, O. purpurea, and O. simia) hybridize when they co-occur. We aimed to characterize patterns of hybridization in O. militaris-O. purpurea, O. purpurea-O. simia, and O. anthropophora-O. simia hybrid zones using molecular and morphological data.
Methods:
We used 11 newly isolated nuclear microsatellites to genotype 695 individuals collected from seven hybrid zones and six allopatric parental populations in France. Geometric morphometric analysis was conducted using 15 labellum landmarks to capture the main aspects of petal shape.
Results:
Backcrossing was asymmetric toward O. militaris in multiple O. militaris-O. purpurea hybrid zones. Hybrids in O. purpurea-O. simia and O. anthropophora-O. simia hybrid zones were largely limited to F1 and F2 generations, but further admixture had occurred. These patterns were reflected in labellum geometric morphometric data, which correlated strongly with nuclear microsatellite data in all three species combinations.
Conclusions:
The coexistence of parental and admixed individuals in these Orchis hybrid zones implies they are likely to be tension zones being maintained by a balance between gene flow into the hybrid zone and selection acting against admixed individuals. The pattern of admixture in the three species combinations suggests intrinsic selection acting on the hybrids is weaker in more closely related taxa.
... Taxon delimitation in orchids still heavily relies on the evaluation of morphological and ecological traits, which can be subject to convergent or parallel evolution and environmental plasticity. Further, taxonomic boundaries can be blurred through hybridisation and introgression, which are frequently observed phenomena in orchids (Dressler 1981;Cozzolino et al. 2006;Pinheiro et al. 2010). ...
This study assessed inter- and intraspecific relationships and genetic structure in an Australian species complex in the helmet orchids (Corybas) to clarify the taxonomic and conservation status of the threatened species Corybas dowlingii, a narrow endemic from southeast Australia. Taxonomic delimitation between the three closely related species C. aconitiflorus, C. barbarae, and C. dowlingii has been mainly based on floral traits which exhibit varying degrees of overlap, rendering species delimitation in the complex difficult. Genome-wide data for the species complex was generated using double-digest restriction-site associated DNA (ddRAD) sequencing. Phylogenomic, genetic network and genetic structure analysis were carried out as well as co-ancestry analysis and hybridisation detection analysis. The ddRADseq results exhibited fine scale genetic structure within the C. acotiniflorus complex and provided evidence for hybridisation and introgression within the complex, resulting in blurred taxonomic boundaries between the three species. Implications of the results for conservation management in the face of hybridisation are discussed.
... Dal punto di vista della loro protezione, gli ambienti di crescita degli ibridi, proprio in quanto sede di processi evolutivi (Cozzolino et al. 2006), sono da conservare attentamente, anche e forse soprattutto nel caso di una presenza diffusa dell'ibrido (o specie di origine ibridogena in formazione). È il caso appunto del nuovo areale distributivo regionale che abbiamo delineato per Orchis ×colemanii, che potrebbe essere classificato come taxon non più "raro", ma "poco comune". ...
si aggiorna la distribuzione nel Lazio (Italia centrale) di Orchis ×colemanii nothosubsp. colemanii (Orchis mascula subsp. mascula × Orchis pauciflora). I dati sono il risultato di ricerche bibliografiche e osservazioni personali. Nel Lazio questo ibrido è stato segnalato come “raro”, ma dai dati presentati risulta diffuso e localmente abbondante, pertanto può essere considerato “poco comune”.
... We searched the literature on orchid hybridization and selected those cases in which both molecular and morphological data were available for all examined individuals. In this way, we selected three orchid hybrid zones: Orchis mascula 9 Orchis pauciflora (hereafter referred to as MAS-PAU; Cozzolino et al., 2006), Anacamptis morio 9 Anacamptis papilionacea (hereafter referred to as MOR-PAP; Moccia et al., 2007) and Anacamptis fragrans 9 Anacamptis robusta (hereafter referred to as FRA-ROB; Ren et al., 2014 and original amplified fragment length polymorphism (AFLP) data collected from the same individuals and reported in the Supporting Information Methods S1, S2). ...
Information on the genetic architecture of phenotypic traits is helpful for constructing and testing models of the ecoevolutionary dynamics of natural populations. For plant groups with long life cycles there is a lack of line cross experiments that can unravel the genetic architecture of loci underlying quantitative traits.
To fill this gap, we propose the use of variation for phenotypic traits expressed in natural hybrid zones as an alternative approach. We used data from orchid hybrid zones and compared expected and observed patterns of phenotypic trait expression in different early‐generation hybrid classes identified by molecular genetic markers.
We found evidence of additivity, dominance, and epistatic interactions for different phenotypic traits.
We discuss the potential of this approach along with its limitations and suggest that it may represent a realistic way to gain an initial insight into the heritability and genomic architecture of traits in organismal groups with complex life history, such as orchids and many others.
... These are solid reasons for special attention to be paid to the protection of this area in the Vitosha Nature Park. Including the area among localities deserving priority conservation measures will save the possibility of further hybridisation in this hybrid zone, as recommended by Cozzolino & al. (2006). (Fig. 33). ...
New chorological data for Bulgarian flora are presented for Dittrichia graveolens (L.) Greuter (Balkan Range, eastern), Hornungia petraea (L.) Rchb. (West Frontier Mts, Mt Vlahina), Spergula pentandra L. (Northern Black Sea Coast), Euphorbia palustris L. (Northern Black Sea Coast), Onobrychis viciifolia Scop. (Northern Black Sea Coast), Centaurium maritimum (L.) R.M. Fritsch (Eastern Rhodopi Mts) and Kickxia commutata subsp. graeca (Bory & Chaub.) R. Fern. (Eastern Rhodopi Mts).
... doi: bioRxiv preprint first posted online Jan. 26, 2020; plasticity. Further, taxonomic boundaries can be blurred through hybridisation and introgression, which are frequently observed phenomena among closely related orchid species (Dressler 1981;Cozzolino et al. 2006;Pinheiro et al. 2010;Nauheimer et al. 2018). ...
This study assessed genomic diversity in an Australian species complex in the helmet orchids to clarify taxonomic delimitation and conservation status of the threatened species Corybas dowlingii, a narrow endemic from southeast Australia. Taxonomic delimitation between the three closely related species C. aconitiflorus, C. barbarae, and C. dowlingii has been mainly based on floral traits which exhibit varying degrees of overlap, rendering species delimitation in the complex difficult. Genomic data for the species complex was generated using double-digest restriction-site associated DNA (ddRAD) sequencing. Maximum likelihood, NeighborNet, and Bayesian structure analyses showed genetic differentiation within the species complex and retrieved genomic signatures consistent with hybridisation and introgression between C. aconitiflorus and C. barbarae, and an intermediate genetic position of C. dowlingii indicating a hybrid origin of the species. The genetic structure analysis showed varying levels of genetic admixture for several C. aconitiflorus, C. barbarae, and C. dowlingii samples, thus further corroborating the presence of hybridisation and introgression within the species complex. The taxonomic status of C. dowlingii D.L.Jones was revised to C. × dowlingii D.L.Jones stat. nov. to reflect its hybrid origin. The conservation status of C. × dowlingii was assessed based on key ecological and ethical aspects, and recommendations made regarding its conservation status in Australian conservation legislation.
... Such hybrid individuals often go unnoticed by botanists and their characteristics are included in the range of variability of one of the parent species. Since these taxa are of great conservation importance, knowing the limits of their variability is crucial in the selection of conservation priorities, such as whether to protect parent, hybrid or both taxa [22][23][24][25]. Therefore, the main goal of this study was to provide a morphological description of three hybrid orchid taxa new to three Central Balkan states and to explore patterns of variability of specific characters in the hybrids relative to the parent species. ...
During floristic investigations of Serbia, Montenegro and North Macedonia from 2011-2018, orchid specimens from the genus Anacamptis, possible hybrids, with characteristics intermediary to species already described for these countries, were discovered. These specimens, together with all potential parent species, were subjected to morphometric analysis in order to determine their hybrid status and characters that distinguished hybrids from parent taxa. Taxonomic studies have included the processing of quantitative and qualitative characters. A total of 60 characters were analyzed, of which 45 quantitative and 15 qualitative. Analysis of quantitative and qualitative characters included 82 specimens – 60 parents and 22 hybrids. Statistical analyses included descriptive and discriminate statistics and multivariate analyses. Hybrid specimens in general had intermediate values of measured characters with different degrees of similarity with one of the parent species. On the other hand, they have higher mean values of some floral characters that may have an evolutionary potential. The possible taxonomic importance of hybrid characters is discussed. Results confirmed that the analyzed specimens are natural orchid hybrids (A. × parvifolia, A. × timbali and A. × gennarii) and represent new plant taxa for the flora of investigated countries. [Project of the Serbian
Ministry of Education, Science and Technological Development, Grant no.
173030]
... In our study, hybrid phenotypes did not have a reproductive advantage over C. parviflorum, despite the range of floral morphologies present in this taxon and their relative rarity (15-20% of the genets in our study populations: Worley & Ford unpublished data). This result contrasts with previous research showing that colour polymorphisms affect insect visitation, with rare phenotypes having a reproductive advantage (Ackerman & Galarza-P erez 1991;Ferdy et al. 1998;Ackerman et al. 2011) or higher pollinator attraction in populations containing parental species and their hybrids (Cozzolino et al. 2006). In our study, hybrid floral phenotypes, visitor abundance and fruit set were all intermediate and increased with higher resemblance to C. parviflorum. ...
Species with rewardless flowers often have low fruit to flower ratios, although wide temporal and spatial variation in fruiting success can occur. We compared floral phenotypes, insect visitors and fruiting success in four populations of the small white ( Cypripedium candidum ) and yellow ( C. parviflorum ) lady’s slipper orchids and their hybrids near the northern extent of North America’s tall grass prairie.
Flower and fruit numbers were observed for two seasons on marked individuals (n = 1811). Floral traits were measured on 82–140 individuals per taxon and analysed in relation to fruiting success. All insects found inside flowers were collected, inspected for pollen smears and measured for comparison to floral features.
Among orchid taxa, C. candidum had the smallest flowers, lowest number and variety of insect visitors, and lowest fruit to flower ratios. These measures were intermediate in hybrids and highest in C. parviflorum , despite low flower numbers in the latter. Within orchid taxa, fruit number was positively related to flower number, but fruit to flower ratios decreased slightly, as would be expected if pollinators left unrewarding patches. Potential pollinators included the dipteran Odontomyia pubescens and hymenopterans Andrena spp . , Apis mellifera and Lasioglossum zonulum .
Cypripedium parviflorum had a reproductive advantage over C. candidum across multiple populations and years. Hybrids showed segregation for floral traits, and hybrid fruiting success increased with a deeper intensity of yellow pigment and larger escape routes for floral visitors. These same attributes likely contributed to the relatively high fruit set in C. parviflorum in the study region.
... These are solid reasons for special attention to be paid to the protection of this area in the Vitosha Nature Park. Including the area among localities deserving priority conservation measures will save the possibility of further hybridisation in this hybrid zone, as recommended by Cozzolino & al. (2006). (Fig. 33). ...
New records for the vascular flora of Inousse (Oinousses) and Lipsi are provided. These islands belong respectively to the Inousses and Lipsi islets groups. The
islets have been studied between 1989 and 1990 for
Inousses (Panitsa & al. 1994) and from 1990 to 1995
for Lipsi (Panitsa & Tzanoudakis 2001). Inousses
comprises six islets situated east of Chios Island (Nomos and Eparchia Chiou in floristic region East Aegean islands) and 270 taxa have been recorded for
this complex: Inousse (the main island with an area
of ca. 14 km²), Panaghia, Vatos, Pontikos, Vatopoula and Archontoniso. Lipsi is a group of 25 islets situated between the islands of Samos, Patmos and Leros (Nomos Dodekanisou, Eparchia Kalimnou, East Aegean islands). The largest island is Lipsi with a floristic count of 471 taxa. The first author (CC) visited Inousse between 11‒18 May 2018 (48 new records belonging to 27 families) and the main island of Lipsi between 21‒26 May 2018 (16 new records belonging to 12 families).
... These are solid reasons for special attention to be paid to the protection of this area in the Vitosha Nature Park. Including the area among localities deserving priority conservation measures will save the possibility of further hybridisation in this hybrid zone, as recommended by Cozzolino & al. (2006). (Fig. 33). ...
... These are solid reasons for special attention to be paid to the protection of this area in the Vitosha Nature Park. Including the area among localities deserving priority conservation measures will save the possibility of further hybridisation in this hybrid zone, as recommended by Cozzolino & al. (2006). (Fig. 33). ...
New records for the vascular flora of Inousse (Oinousses) Lipsi and Ikaria are provided.
... These are solid reasons for special attention to be paid to the protection of this area in the Vitosha Nature Park. Including the area among localities deserving priority conservation measures will save the possibility of further hybridisation in this hybrid zone, as recommended by Cozzolino & al. (2006). (Fig. 33). ...
New chorological data are presented for 401 species and subspecies from Bulgaria (15-18, 130-148, 184-205, 390-392, 398-401), Greece (1-3, 19-129, 149-183, 206-389, 393-397), and Turkey-in-Europe (4-14). The taxa belong to the following families: Acanthaceae (149), Aceraceae (55, 242), Aizoaceae (150), Alliaceae (17, 46, 47, 120, 378, 379), Amaranthaceae (56, 61, 62), Amaryllidaceae (180), Anacardiaceae (243), Apiaceae (15, 20, 21, 63-67, 142, 151-153, 187, 206, 244-252, 393), Apocynaceae (253, 254), Araceae (48), Aristolochiaceae (255), Asclepiadaceae (68, 154), Asparagaceae (380), Asphodelaceae (381), Asteraceae (4-8, 22-25, 57, 69-79, 130-132, 155-158, 188, 199, 207-212, 256-277, 394), Balsaminaceae (133, 134, 189), Berberidaceae (190), Boraginaceae (9, 10, 26, 80, 159-161, 278), Brassicaceae (27, 28, 81, 82, 143, 162-164, 200, 279-282), Buddlejaceae (135, 191, 213), Cactaceae (83, 124, 197, 283), Caesalpiniaceae (284), Campanulaceae (29, 30, 285-287), Caprifoliaceae (84, 288, 289), Caryophyllaceae (1, 31, 85, 165, 166, 201, 214-216, 290-294), Ceratophyllaceae (217), Chenopodiaceae (2, 32, 86-88, 136, 167, 168, 218), Colchicaceae (18), Convolvulaceae (11, 16, 33, 34, 89, 219, 295-297), Crassulaceae (125, 298), Cucurbitaceae (35, 90, 299), Cyperaceae (49), Dennstaedtiaceae (241), Dipsacaceae (91, 300-303), Dioscoreaceae (382), Ericaceae (92), Euphorbiaceae (36, 58, 59, 93, 94, 169, 192, 193, 202, 304-306), Fabaceae (95, 96, 137-139, 170, 171, 194, 203, 307-323, 395), Frankeniaceae (97), Gentianaceae (37, 98, 99, 204, 324), Geraniaceae (325), Hyacinthaceae (181), Hydrophyllaceae (100), Hypericaceae (101, 326), Iridaceae (129, 182, 198), Juncaceae (50, 183, 233), Lamiaceae (38, 102, 144, 172, 220-223, 327-334), Liliaceae s.l. (51, 147), Linaceae (103, 104, 145, 335), Lythraceae (39, 105), Malvaceae (106, 107, 224, 225, 336), Moraceae (337-339), Nyctaginaceae (340), Oleaceae (341, 342), Onagraceae (40, 226-228), Orchidaceae (148, 184, 185, 390-392, 398-401), Orobanchaceae (41, 108, 109, 173, 174, 343, 344, 396), Oxalidaceae (42, 345, 346), Papaveraceae (110), Phytolaccaceae (348), Pinaceae (186, 196), Platanaceae (347), Plumbaginaceae (111, 126, 349), Poaceae (52-54, 121-123, 234-240, 383-388), Polygalaceae (350), Polygonaceae (43, 60, 140, 229, 351, 352), Primulaceae (353), Pteridaceae (19), Rafflesiaceae (175), Ranunculaceae (44, 45, 176, 177, 230, 354-356), Resedaceae (357), Rosaceae (127, 358-360), Rubiaceae (146, 231, 361-363, 397), Rutaceae (112), Salicaceae (364), Sapindaceae (141), Saxifragaceae (178), Scrophulariaceae s.l. (12-14, 113, 128, 205, 365, 366), Smilacaceae (389), Solanaceae (3, 114, 179, 367, 368), Tiliaceae (369), Ulmaceae (370), Urticaceae (115, 116, 371), Valerianaceae (372, 373), Verbenaceae (117, 374, 375), Veronicaceae (118, 232, 376, 377), Vitaceae (195), and Zygophyllaceae (119).
N
ew species for countries are: Bulgaria – Anacamptis coriophora × A. morio (390), Gymnadenia conopsea s.l. × G. rhellicani (391), Neotinea ×dietrichiana (184, 401), Greece – Buddleja davidii (213), Euphorbia humifusa (36).
Th
e publication includes contributions by: E. Axiotis, M. Axiotis & Kit Tan (1-3), M. Aybeke (4-14), Zh. Barzov & A. Petrova (15-18), B. Biel & Kit Tan (19-54), C. Cattaneo & M. Grano (55-60), C. Cattaneo & M. Panitsa (61-123), K. Giannopolous, Kit Tan & G. Vold (124-129), P. Glogov, M. Georgieva & D. Pavlova (130-141), P. Glogov & D. Pavlova (142-147), I. Hristov, M. Yordanova, A. Petrova & A. Kurteva (148), R. Marchant, Kit Tan & A. Strid (149-183), A. Petrova, R. Bukova & P. Dimitrov (184), A. Petrova, R. Varbanov & A. Shishkova (185), A. Petrova, D. Venkova, I. Gerasimova & R. Vassilev (186-195), Ts. Raycheva & K. Stoyanov (196-198), S. Stoyanov, V. Goranova & Zh. Barzov (199-205), A. Strid (206-240), Kit Tan & G. Vold (241-389), V. Vladimirov, S. Bancheva & M. Delcheva (390-391), V. Vladimirov & Z. Szeląg (392), G. Zarkos, V. Christodoulou, Kit Tan & G. Vold (393-397) , I. Kostadinov, S. Dalakchieva & K. Popov (398-401).
... La specie ha reagito a questa modifica insediandosi anche in habitat di transizione e coltivi: è rinvenibile infatti anche su superfici olivetate non interessate da lavorazioni profonde del terreno e dall'uso intensivo di erbicidi e insetticidi, come tra le chiarìe delle formazioni di macchia mediterranea che si avvicendano ad aree boschive interessate ciclicamente da incendi. Studi recenti pongono in questione l'elaborazione di strategie di conservazione basate sulla salvaguardia di singole specie; in alcuni casi queste andrebbero probabilmente affiancate a strategie oculate di salvaguardia dei siti nei quali le potenzialità ibridogene risultano particolarmente spiccate (Cozzolino et al. 2006), proprio perché questi processi di ibridazione possono rappresentare per le specie un'occasione per incamerare fattori genetici utili dal punto di vista adattivo. ...
... It is therefore not a surprise to see these processes frequently cited in several plant studies focused on Mediterranean groups (e.g. Armeria Willd., Tauleigne-Gomes & Lef ebvre 2005; Narcissus L., Santos-Gally et al. 2012; Orchis L., Cozzolino et al. 2006; Phlomis L., Albaladejo & Aparicio 2007;Centaurium Hill, Mansion et al. 2005; among many others). Still, to date, there are no estimations of the frequency of hybridisation and polyploidisation in the Mediterranean region, and accessing them is particularly challenging given the diversity of the Mediterranean at several levels. ...
Natural hybridization and polyploidy are currently recognized as drivers of biodiversity despite early sceptical views about their importance. The Mediterranean region is a biodiversity hotspot where geological and climatic events have created numerous opportunities for speciation through hybridization and polyploidy. Still, our knowledge on the frequency of these mechanisms in the region is largely limited, despite both phenomena have been frequently cited in studies of Mediterranean plants. In this manuscript, we reviewed the information available from biodiversity and cytogenetic databases to provide the first estimates of hybridization and polyploidy frequency in the Mediterranean region. We have also inspected the most comprehensive modern Mediterranean Flora (Flora iberica) to survey the frequency and taxonomic distribution of hybrids and polyploids in Iberian Peninsula. We found that less than 6% of Mediterranean plants were hybrids, although a higher frequency was estimated for the Iberian Peninsula (13%). Hybrids were concentrated in a few families and in even fewer genera. The overall frequency of polyploidy (36.5%) was comparable with previous estimates in other regions, however our estimates increased when analysing the Iberian Peninsula (48.8%). A surprisingly high incidence of species harboring two or more ploidy levels was also observed (21.7%). A review of the available literature also showed that the ecological factors driving the emergence and establishment of new entities are still poorly studied in the Mediterranean flora, although geographical barriers seem to play a major role in polyploid complexes. Finally, this study reveals several gaps and limitations in the current knowledge about the frequency of hybridization and polyploidy in the Mediterranean region. The obtained estimations might change in the future with the increasing number of studies; still, rather than setting the complete reality, we hope that this work triggers future studies about hybridization and polyploidy in the Mediterranean region.
... Hipóteses sobre os mecanismos de especiação podem ser levantadas e testadas. Processos de especiação que ainda não foram totalmente concluídos podem ser identificados e novas ideias podem ser formuladas (Cozzolino et al., 2006;Baack e Rieseberg, 2007). ...
Artigo Experimentos de cruzamentos recíprocos como ferramenta para avaliar o isolamento reprodutivo numa zona de hibridação natural da família Orchidaceae Juss. Recebido: 15set14 Aceito: 08jan15 Publicado: 30jul15 Revisado por Déborah Yara Alves Cursino dos Santos e Anônimos Resumo. Híbridos são descendentes do cruzamento entre indivíduos de duas espécies cujas barreiras reprodutivas não estão completamente estabelecidas. Hibridação é particularmente comum em certos gêneros da família Orchidaceae. Na Serra dos Órgãos no estado do Rio de Janeiro ocorrem em simpatria duas espécies irmãs do gênero Epidendrum: E. secundum Jacq e E. xanthinum Lindl, além de indivíduos com caracteres intermediários, supostos híbridos. Neste trabalho avaliamos a hipótese de hibridação e a intensidade do isolamento reprodutivo entre estas espécies. Utilizando experimentos de polinização recíproca foi possível detectar hibridação entre as espécies. O baixo sucesso reprodutivo dos híbridos formados é uma importante barreira reprodutiva que promove isolamento reprodutivo forte o suficiente para manter a coesão destas espécies. Abstract. Hybrids are individuals formed when reproductive barriers between closely related species aren't totally established, and individuals from different species cross. Hybridization is remarkably common in some genus within the Orchidaceae family. On Serra dos Órgãos, Rio de Janeiro, two sister species from the genus Epidendrum: E. secundum Jacq e E. xanthinum Lindl occur sympatrically. Individuals with intermediate traces, supposedly hybrids, also occur. In this work, we evaluate the hypothesis of hybridization between these two species and the intensity of their reproductive isolation. It was possible to detect hybridization using experiments of reciprocal pollination. The low reproductive success observed on hybrid individuals plays a major role as a barrier that promotes reproductive isolation strong enough to maintain these two species apart. Introdução Zonas de hibridação O estudo de zonas de hibridação tem ajudado Biólogos a compreender a origem e intensidade das barreiras repro-dutivas entre espécies. Zonas de hibridação são regiões ge-ográficas onde duas ou mais espécies ocorrem em simpatria (ocorrendo na mesma região), e os indivíduos de suas po-pulações entram em contato. Diversos estudos realizados em zonas de hibridação natural entre plantas tem sido realizados tanto na América quanto na Europa, tais estudos envolvem geralmente uma abordagem multidisciplinar. Os objetivos e métodos utilizados são bastante variados e vão desde o uso de marcadores moleculares em DNA nuclear e/ou plastidial, neste caso com o objetivo de evidenciar a produção de híbri-dos através de identificação da estrutura genética das popu-lações em contato (Pinheiro et al., 2010; Moraes et al.,2013; Vega et al., 2013), até experimentos com ênfase em aspectos ecológicos como, por exemplo, identificação de agentes po-linizadores (Pansarin e Amaral, 2008), em alguns casos tem sido realizados experimentos envolvendo a biologia repro-dutiva, neste caso polinizações manuais são conduzidas em plantas que se encontram em cultivo em coleções biológicas para se inferir a compatibilidade reprodutiva das espécies em contato (Scopece et al., 2007; Scopece et al., 2008; Pinheiro et al., 2010; Pinheiro et al., 2013). Em plantas é comum que espécies filogeneticamente relacionadas ocorrendo numa mesma localidade experimen-tem fluxo de pólen recíproco, o que pode levar a formação de descendentes de natureza híbrida. Híbridos são indivíduos que, em geral, apresentam características morfológicas inter-mediárias entre as características de suas espécies parentais, com genomas compostos pela mistura genética das duas es-pécies em questão (Cozzolino e Widmer, 2005) Revista da Biologia (2015) 14(1):17-23
... For example, Azevedo et al. (2006) analysed hybridisation between two species of Bulbophyllum Thouars (1822: t. 3) (Orchidaceae) by means of alloenzymatic markers. Similarly, Cozzolino et al. (2006) and Schulte et al. (2010) assessed hybridisation processes through AFLP technique, respectively in Mediterranean orchid species and Andean taxa of Puya. Isoda et al. (2000) analysed Japanese species of Abies Miller (1754: without page) (Pinaceae) using plastid, mitochondrial and nuclear DNA markers, and Ayres et al. (2008) studied the hybridisation between native and introduced species of Spartina Schreber (1789: 43) (Poaceae) in California by means of plastid and nuclear DNA analyses. ...
Natural hybridisation is considered a common fact among species of Bromeliaceae. We here report natural hybridisation between two sympatric Vriesea species, V. incurvata and V. carinata, in the Atlantic Forest of Santa Catarina (southern Brazil), one of the main remnants of the Mata Atlântica forest. Morphological and genetic data were obtained from both parental species and the putative hybrid, individuals of the latter being found to be intermediate between those of the parents. The main differential characters of the nothospecies were the width of the inflorescence and the rachis, length and width of the stigma, and the length of anthers. Moreover, plastid markers and nuclear microsatellites were analysed and we found that the hybrid plants shared genetic information with both parental species, although they showed an overall higher genetic similarity with V. carinata. As a conclusion, the hybrid status of the intermediate plants is accepted and therefore the new nothospecies V. × brueggemannii is described. To date, the presence of the hybrids is restricted to regeneration sites, a fact that points out to the need for preservation of the secondary vegetation as an effective tool for conservation of biodiversity.
... For example, Azevedo et al. (2006) analysed hybridisation between two species of Bulbophyllum Thouars (1822: t. 3) (Orchidaceae) by means of alloenzymatic markers. Similarly, Cozzolino et al. (2006) and Schulte et al. (2010) assessed hybridisation processes through AFLP technique, respectively in Mediterranean orchid species and Andean taxa of Puya. Isoda et al. (2000) analysed Japanese species of Abies Miller (1754: without page) (Pinaceae) using plastid, mitochondrial and nuclear DNA markers, and Ayres et al. (2008) studied the hybridisation between native and introduced species of Spartina Schreber (1789: 43) (Poaceae) in California by means of plastid and nuclear DNA analyses. ...
Natural hybridisation is considered a common fact among species of Bromeliaceae. We here report natural hybridisation between two sympatric Vriesea species, V. incurvata and V. carinata, in the Atlantic Forest of Santa Catarina (southern Brazil), one of the main remnants of the Mata Atlântica forest. Morphological and genetic data were obtained from both parental species and the putative hybrid, individuals of the latter being found to be intermediate between those of the parents. The main differential characters of the nothospecies were the width of the inflorescence and the rachis, length and width of the stigma, and the length of anthers. Moreover, plastid markers and nuclear microsatellites were analysed and we found that the hybrid plants shared genetic information with both parental species, although they showed an overall higher genetic similarity with V. carinata. As a conclusion, the hybrid status of the intermediate plants is accepted and therefore the new nothospecies V. × brueggemannii is described. To date, the presence of the hybrids is restricted to regeneration sites, a fact that points out to the need for preservation of the secondary vegetation as an effective tool for conservation of biodiversity.
... Our morphological observations concur with the initial hybrid taxon description and drawings published by Kerner (1865). The parent species flowers opening order is documented by Delforge (2006) Cozzolino et al. (2006) researched a hybrid zone of closely related parent species of the Orchis genus and concluded that the backcrossing is rare or absent and that vast majority of hybrids belong to the first generation. Such an outcome is explained by the reduced fertility of the hybrids (Jacquemyn et al. 2012b). ...
In 2015 two new orchid taxa were observed for the first time inside the Natura 2000 site „Vejalnica and Krč“ (SE slopes of the Medvednica Mt., NE of the Croatian capital Zagreb). These are: Orchis simiaLam. and Orchis ×beyrichii(Rchb.f.) A.Kern. This is the first recent find of O. simia at eastern Medvednica and the first find of O. ×beyrichiifor continental Croatia. Observed morphologi-cal variations and differences between the parent species and the hybrid are systematised and dis-cussed with respect to other published hybrid zone research results.
---
Tijekom 2015. uočene su dvije nove svojte unutar područja Natura 2000 „Vejalnica i Krč“ (JI padine planine Medvednica, SI od glavnog grada Hrvatske, Zagreba). To su: Orchis simiaLam. i Orchis ×beyrichii(Rchb.f.) A.Kern. Ovo je prvi recentni nalaz vrste O. simia na području istočne Medvednice te prvi nalaz hibridne svojte O. ×beyrichiiza kontinentalnu Hrvatsku. Sistematizira se opažene morfološke varijacije i razlikovne značajkeizmeđu roditeljskih vrsta i hibrida te diskutira u odnosu na rezultate drugih istraživanja o hibridnim zonama.
Hybridization is one of the key processes shaping lineage diversification, particularly in regions that experienced strong climate oscillations. The alpine biome with its rich history of glacial-interglacial cycles and complex patterns of species distribution shifts offers an excellent system to investigate the impact of gene flow on population dynamics and speciation, important issues for evolutionary biology and biodiversity conservation. In this study, we combined genomic data (DArTseq), chloroplast markers, and morphology to examine phylogenetic relationships and the permeability of species boundaries and their evolutionary outcomes among the alpine extremophilic species of Puccinellia (Poaceae) in the Pamir Mountains, a part of the Mountains of Central Asia biodiversity hotspot. We determined the occurrence of interspecific hybrids between P. himalaica and P. pamirica, which demonstrated almost symmetric ancestry from their parental species and did not show signals of introgression. According to our integrative revision, the natural hybrids between P. himalaica and P. pamirica should be classified as Puccinellia ×vachanica (pro species). Using approximate Bayesian computation for population history inference, we uncovered that P. himalaica hybridized with P. pamirica independently in multiple localities over the Holocene. Hybrids inherited the fine-scale genetic structure from their parental species, which developed these patterns earlier, during the Late Pleistocene. Hybridization had different consequences for the involved parental lineages, likely playing an important role in a continuing decline of P. himalaica in the Pamir Mountains over the Holocene. Our results show that P. himalaica should be considered a critically endangered species in the Pamir Mountains and could also be retreating across its entire range of distribution in High Mountain Asia. Using a comparative phylogeographic framework, we revealed the risk of extinction of a cold-adapted alpine species in a global biodiversity hotspot. This study highlights that genomics could unravel diversity trends under climate change and provides valuable evidence for conservation management.
The Platanthera Rich. (Orchidoideae) comprise a speciose genus of orchids primarily in the northern hemisphere, with up to 200 known species worldwide. Individual species are known to self‐pollinate, but many rely on insect pollinators with characteristics such as floral color, timing of floral odor emissions, nectar rewards, and spur length associated with particular pollination syndromes. As with many orchids, some orchid–pollinator associations are likely highly co‐evolved, but we also know that some Platanthera spp. are the result of hybridization events, which implies a lack of pollinator fidelity in some cases. Some Platanthera spp. occur in large numbers which, coupled with the numerous Platanthera –pollinator systems, make them accessible as study species and useful for co‐evolutionary studies. Due to the likely effects of climate change and ongoing development on Platanthera spp. habitats, these orchids and their associated pollinators should be a focus of conservation attention and management. However, while there is a fairly substantial literature coverage of Platanthera –pollinator occurrence and interactions, there are still wide gaps in our understanding of the species involved in these systems. In this systematic review, we outline what is current knowledge and provide guidance on further research that will increase our understanding of orchid–insect co‐evolutionary relationships. Our review covers 157 orchid species and about 233 pollinator species interacting with 30 Platanthera spp. We provide analyses on aspects of these interactions such as flower morphology, known insect partners of Platanthera species, insect‐ Platanthera specificity, pollination visitor timing (diurnal vs. nocturnal), floral rewards, and insect behavior affecting pollination outcomes (e.g., pollinia placement). A substantial number of Platanthera spp. and at least a few of their known pollinators are of official (IUCN) conservation concern – and many of their pollinators remain unassessed or even currently unknown – which adds to the urgency of further research on these co‐evolved relationships.
A new hybrid of the genus Ophrys is described between O. incubacea and O. tenthredinifera.
Paphiopedilum is a popular and horticulturally important orchid and is also known as lady’s slipper orchid. The genus is widely traded as cut flowers and potted plants due to its spectacularly beautiful flowers with a long shelf-life. Due to market demands, the orchids of this genus has been collected excessively leading to endangerment to its wild populations. Propagation of this orchid for commercialization through the conventional method has a slow growth rate, low seed germination rate and requires the association of mycorrhizal fungi for germination. Hence, in vitro propagation or micropropagation provides an alternative approach in meeting the needs for sustainable commercial demand and also in the conservation of wild slipper orchids. This chapter aims to discuss the latest research progress on in vitro propagation and acclimatization of Paphiopedilum orchids.
Orchids often have specific pollinators, which should provide reproductive isolation, yet many produce natural hybrids. Platanthera dilatata and P. stricta differ in floral morphology but often co-occur, overlap in flowering, and are reputed parents of P. x estesii . We used motion-triggered video detection units to monitor floral visitors of P. dilatata and P. stricta on Vancouver Island, Canada. Pollinia removal in P. dilatata was observed using histochemical staining, and cross-pollinations were performed to determine compatibility. From 1,152 h, 753 videos were recorded; 655 contained insects and 91 contained arachnids. Bumblebees, butterflies, and moths removed pollinia from P. dilatata . No pollinia removal was observed from P. stricta . Five videos showed insects moving between Platanthera species. Pollinia removal rates were low. Hand-pollinations resulted in capsule development and seed production. This study adds to the known diversity of insects interacting with these orchids, and highlights regional differences in floral visitors.
Interspecific hybridization is one of the most controversial—and usually neglected—issues in conservation due to its multiple evolutionary consequences that might include the origin and transfer of adaptations, the blur of distinctive lineages or the formation of maladaptive hybrids. However, despite different outcomes, most conservation laws do not offer any possibility of hybrids being protected since they are perceived as a threat to the survival of pure species. We assessed how much hybridization has contributed to species extinction considering all IUCN Red Data assessments. However, we found that it has been scarcely reported as a threat contributing to extinction: only 11 extinct species out of 120,369 assessments mentioned hybridization. Although the causes that contribute to species extinctions should be controlled, the reasons for not conserving hybrids seem subjective rather than empirically supported. In a genomic era where hybridization is being more frequently detected, the debate involving the conservation of hybrids should be re-opened. Should we conserve hybrids despite the possibility of gene flow with parental species? Should we protect only natural hybrids? The resolution of this debate goes to the heart of what we mean to conserve and the time scale of conservation. But hybridization is part of the evolutionary process and might even increase in the future due to human-induced changes. As such, it becomes clear that we need to move beyond the causes and instead tackle the consequences of hybridization to create environmental policies for the management of hybrids, considering both positive and negative consequences.
Platanthera bifolia and P. chlorantha are terrestrial and rewarding orchids with a wide Eurasian distribution. Although genetically closely related, they exhibit significant morphological, phenological and ecological differences that maintain reproductive isolation between the species. However, where both species co-occur, individuals with intermediate phenotypic traits, often considered as hybrids, are frequently observed. Here, we combined neutral genetic markers (AFLPs), morphometrics and floral scent analysis (GC-MS) to investigate two mixed Platanthera populations where morphologically intermediate plants were found. Self-pollination experiments revealed a low level of autogamy and artificial crossings combined with assessments of fruit set and seed viability, showed compatibility between the two species. The results of the genetic analyses showed the same genetic patterns of morphologically intermediate individuals with the P. bifolia group . These results are corroborated also by floral scent analyses, which confirmed a strong similarity in floral scent composition between intermediate morphotypes and P. bifolia . Therefore, this study provided a much more detailed picture of the genetic structure of a sympatric zone between two closely allied species and supports the hypothesis that intermediate morphotypes in sympatry could reflect an adaptive evolution in response to local pollinator-mediated selection.
Platanthera bifolia and P. chlorantha are terrestrial and rewarding orchids with a wide Eurasian distribution. Although genetically closely related, they exhibit significant morphological, phenological and ecological differences that maintain reproductive isolation between the species. However, where both species co-occur, individuals with intermediate phenotypic traits, often considered as hybrids, are frequently observed. Here, we combined neutral genetic markers (AFLPs), morphometrics and floral scent analysis (GC-MS) to investigate two mixed Platanthera populations where morphologically intermediate plants were found. Self-pollination experiments revealed a low level of autogamy and artificial crossings combined with assessments of fruit set and seed viability, showed compatibility between the two species. The results of the genetic analyses showed the same genetic patterns of morphologically intermediate individuals with the P. bifolia group . These results are corroborated also by floral scent analyses, which confirmed a strong similarity in floral scent composition between intermediate morphotypes and P. bifolia . Therefore, this study provided a much more detailed picture of the genetic structure of a sympatric zone between two closely allied species and supports the hypothesis that intermediate morphotypes in sympatry could reflect an adaptive evolution in response to local pollinator-mediated selection.
Temperature rise due to climate change is putting many arctic and alpine plants at risk of extinction because their ability to react is outpaced by the speed of climate change. We considered assisted species migration (ASM) and hybridization as methods to conserve cold‐adapted species (or the genes thereof) and to minimize the potential perturbation of ecosystems due to climate change. Assisted species migration is the deliberate movement of individuals from their current location to where the species’ ecological requirements will be matched under climate projections. Hybridization refers to crossbreeding of closely related species, where for arctic and alpine plants, 1 parent is the threatened cold‐adapted and the other its reproductively compatible, warm‐adapted sibling. Traditionally, hybridization is viewed as negative and leading to a loss of biodiversity, even though hybridization has increased biodiversity over geological times. Furthermore, the incorporation of warm‐adapted genes into a hybrid may be the only means for the persistence of increasingly more maladapted, cold‐adapted species. If approached with thorough consideration of fitness‐related parameters of the source population and acknowledgement of the important role hybridization has played in shaping current biodiversity, ASM and hybridization could help save partial or whole genomes of key cold‐adapted species at risk due to climate change with minimal negative effects on ecosystem functioning.
The morphologically overlapping and frequently syntopic species of Spiranthes (Orchidaceae) found in the Sierra Nevada of California and Cascade Range of Oregon—S. porrifolia, S. romanzoffiana, and S. stellata—have long been a source of taxonomic confusion. Much of this confusion is attributed to hypothesized hybridization between species, and a lack of agreement concerning the distinctiveness of S. stellata from S. romanzoffiana. We used molecular phylogenetics incorporating low‐copy nuclear, nuclear ribosomal, and chloroplast DNA sources, in addition to morphological data, to clarify the evolutionary relationships of this complex. Our results indicate that contrary to long‐held hypotheses, hybridization between S. porrifolia and S. romanzoffiana appears to be rare or absent. Furthermore, a realignment of taxon status is necessary for S. stellata subsp. stellata and S. stellata subsp. perexilis, with subsp. perexilis elevated to full non‐hybrid species rank as S. perexilis comb. & stat. nov., and subsp. stellata changed to S. ×stellata, indicating its likely recurrent allopolyploid origin between the sister species S. perexilis and S. romanzoffiana. We also describe S. ×sierrae nothosp. nov., representing rare allopolyploid hybrids between S. perexilis and S. porrifolia, and provide the first pollinator records for S. perexilis and S. ×stellata.
In six 42-chromosomes taxa belonging to genus Orchis s. l. heterochromatin location and distribution and staining properties were analysed by means of C-banding and of the fluorochromes 4’-6-diamidino-2-phenylindole-2HCl (DAPI) and Hoechst 33258. Most species could be distinguished on the basis of heterochromatin amounts and distribution. In the species O. mascula and O. provincialis most DAPI-positive sites did not co-localize with C-bands. DAPI revealed bright fluorescence at telomeric or subtelomeric regions of numerous chromosomes of O. mascula and particularly large/bright blocks at the telomeres of O. provincialis. In O. x penzigiana (Orchis mascula ssp. ichnusae x O. provincialis) overall heterochromatin distribution followed that of the parental species. In Neotinea group all DAPI positive bands co-localize with C-bands, but have different distribution in the taxa analysed. Present and literature data indicate a high level of plasticity of heterochromatin organization in Orchis s. l., and suggest evolutionary pathways in agreement with recent molecular data.
Clines across hybrid zones can be produced by several forms of natural selection. We illustrate an approach to studying pollinator-mediated selection in plant hybrid zones, using two species of Ipomopsis (Polemoniaceae) as a model system. We measured visitation to flowers in natural and experimental populations by two major types of pollinators, hummingbirds and hawkmoths, at up to three different spatial scales. Using measures of pollinator visitation, we calculated phenotypic selection gradients and characterized the form of selection in the hybrid zone. Hummingbirds overvisited Ipomopsis aggregata compared with Ipomopsis tenuituba and morphological hybrids at all spatial scales, especially the largest scale of kilometers. These responses may depend in part on the presence of other hummingbird-visited plants in the community. Hummingbird behavior produced directional selection favoring wide corolla tubes and intense red coloration. Hawkmoths, in contrast, overvisited plants with narrow corolla tubes. When both types of pollinators were present, corolla width experienced disruptive selection, consistent with a model of hybrid disadvantage, in the natural hybrid zone, however, hawkmoths are rare participants. In most years plants experience visitation from hummingbirds alone. Thus, selection by pollinators usually fits an advancing wave model in which traits characteristic of I. aggregata are favored everywhere. Modeling the evolution of clines in response to such pollinator-mediated selection will require further theoretical development that allows for selection intensity to vary with spatial scale and with the abundance of unrelated plants visited by the same pollinators.
Outlines the nature of Mullerian mimicry, where there has been convergence of traits whereby plants mutually benefit by sharing the same advantages (in this case pollination), and examines more fully the nature and implications of Batesian mimicry, viz where a relatively rare species that provides no reward mimics flowers of a more abundant species that does reward a pollinator. Discussion centres on reproductive deception, in terms of both imitation of oviposition substrate and sexual deceit. -P.J.Jarvis
Internal transcribed spacer (ITS nuclear rDNA) data have been obtained from 190 terrestrial orchid species, encompassing all genera and the great majority of the widely recognized species of Orchidinae, a heterogeneous selection of species of Habenariinae, and single species of Satyriinae and Disinae (the latter serving as outgroup). The resulting parsimony-based phylogeny reveals 12 well-resolved clades within the Orchidinae, based on Anacamptis s.l., Serapias, Ophrys, Steveniella–Himantoglossum s.l. (including ‘Comperia’ and ‘Barlia’, most species being 2n = 36), Neotinea s.l., Traunsteinera–Chamorchis, Orchis s.s., Pseudorchis–Amerorchis–Galearis–Neolindleya–Platanthera s.l. (most 2n = 42), Dactylorhiza s.l., Gymnadenia s.l. (most 2n = 40, 80), Ponerorchis s.l.–Hemipilia s.l.–Amitostigma–Neottianthe, and Brachycorythis (most 2n = 42). Relationships are less clearly resolved among these 12 clades, as are those within Habenariinae; the subtribe appears either weakly supported as monophyletic or as paraphyletic under maximum parsimony, and the species-rich genus Habenaria is clearly highly polyphyletic. The triphyly of Orchis as previously delimited is confirmed, and the improved sampling allows further generic transfers to Anacamptis s.l. and Neotinea s.l. In addition, justifications are given for: (1) establishing Steveniella as the basally divergent member of an appreciably expanded Himantoglossum that incorporates the former genera ‘Barlia’ and ‘Comperia’, (2) reuniting ‘Piperia’ with a broadly defined Platanthera as section Piperia, necessitating ten new combinations, (3) broadening Ponerorchis to include Chusua, and Hemipilia to include single ‘orphan’ species of Ponerorchis and Habenaria, and (4) recognizing ‘Gymnadenia’camtschatica as the monotypic Neolindleya camtschatica within the Pseudorchis∼Platanthera clade. Few further generic transfers are likely in Orchidinae s.s., but they are anticipated among habenariid genera, on acquisition of additional morphological and molecular evidence; one probable outcome is expansion of Herminium. Species-level relationships are also satisfactorily resolved within most of the major clades of Orchidinae, with the notable exceptions of Serapias, the derived sections of Ophrys, Himantoglossum s.s., some sections within Dactylorhiza, the former genus ‘Nigritella’ (now tentatively placed within Gymnadenia s.l.), Hemipilia s.l., and possibly Ponerorchis s.s. Relationships among the 12 major clades broadly accord with bona fide records of intergeneric hybridization. Current evidence supports the recently recognized 2n = 36 clade; it also indicates a 2n = 40 clade that is further diagnosed by digitate root-tubers, and is derived relative to the recently recognized clade of exclusively Asian genera (Ponerorchis s.l.–Hemipilia s.l.–Amitostigma–Neottianthe). This in turn appears derived relative to the Afro-Asiatic Brachycorythis group; together, these two clades identify the plesiomorphic chromosome number as 2n = 42. If the African genus Stenogolottis is correctly placed as basally divergent within a monophyletic Habenariinae, the tribe Orchideae and subtribes Orchidinae and Habenariinae could all have originated in Africa, though in contrast the Asiatic focus of the basally divergent members of most major clades of Orchidinae suggests an Asiatic radiation of the subtribe. Morphological characters informally ‘mapped’ across the molecular phylogeny and showing appreciable levels of homoplasy include floral and vegetative pigmentation, flower shape, leaf posture, gynostemium features, and various pollinator attractants. Qualitative comparison of, and reciprocal illumination between, degrees of sequence and morphological divergence suggests a nested set of radiations of progressively decreasing phenotypic magnitude. Brief scenarios, both adaptive and non-adaptive, are outlined for specific evolutionary transitions. Recommendations are made for further species sampling, concentrating on Asian Orchidinae (together with the Afro-Asiatic Brachycorythis group) and both Asian and Southern Hemisphere Habenariinae, and adding plastid sequence data. Taxonomic changes listed are: Anacamptis robusta (T.Stephenson) R.M.Bateman, comb. nov., A. fragrans (Pollini) R.M.Bateman, comb. nov., A. picta (Loiseleur) R.M.Bateman, comb. nov., Neotinea commutata (Todari) R.M.Bateman, comb. nov., N. conica (Willdenow) R.M.Bateman, comb. nov., Platanthera elegans Lindley ssp. maritima (Rydberg) R.M.Bateman, comb. nov., P. elegans Lindley ssp. decurtata (R.Morgan & Glicenstein) R.M.Bateman, comb. nov., P. elongata (Rydberg) R.M.Bateman, comb. nov., P. michaelii (Greene) R.M.Bateman, comb. nov., P. leptopetala (Rydberg) R.M.Bateman, comb. nov., P. transversa (Suksdorf) R.M.Bateman, comb. nov., P. cooperi (S.Watson) R.M.Bateman, comb. nov., P. colemanii (R.Morgan & Glicenstein) R.M.Bateman, comb. nov., P. candida (R.Morgan & Ackerman) R.M.Bateman, comb. nov. and P. yadonii (R.Morgan & Ackerman) R.M.Bateman, comb. nov. © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society, 2003, 142, 1–40.
Four plastid markers, four nuclear markers and 14 morphometric characters were used in this study to investigate the evolution of Dactylorhiza baltica (Orchidaceae) in European Russia. In total, 98, 214 and 775 samples from 85, 112 and 121 populations were involved in the combined and separate molecular and morphometric analyses, respectively. In most cases, morphometric measures were done on exactly the same plants that were used for DNA studies. Dactylorhiza baltica plants from European Russia are most probably the products of several recent and mostly local hybridization events between the diploids D. fuchsii and D. incarnata, which have each been the maternal parent on different occasions. Considerable introgression into the parental diploids via the allopolyploid D. baltica is also hypothesized. Several morphological characters, such as length of the lip lateral lobe and the length of longest leaf, were found to be robust and could be useful in identification of D. baltica. This study demonstrates the advantage of ‘combined’ techniques, especially in the case of taxonomically complex taxa. © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society, 2005, 147, 257–274.
Rates of hybridization and introgression are increasing dramatically worldwide because of translocations of organisms and habitat modifications by humans. Hybridization has contributed to the extinction of many species through direct and indirect means. However, recent studies have found that natural hybridization has played an important role in the evolution of many plant and animal taxa. Determining whether hybridization is natural or anthropogenic is crucial for conservation, but is often difficult to achieve. Controversy has surrounded the setting of appropriate conservation policies to deal with hybridization and introgression. Any policy that deals with hybrids must be flexible and must recognize that nearly every situation involving hybridization is different enough that general rules are not likely to be effective. We provide a categorization of hybridization to help guide management decisions
Multivariate statistical methods are derived for measuring selection solely from observed changes in the distribution of phenotypic characters in a population within a generation. Selective effects are readily detectable in characters that do not change with age, such as meristic traits or adult characters in species with determinate growth. Ontogenetic characters, including allometric growth rates, can be analyzed in longitudinal studies where individuals are followed through time. Following an approach pioneered by Pearson (1903), this analysis helps to reveal the target(s) of selection, and to quantify its intensity, without identifying the selective agent(s). By accounting for indirect selection through correlated characters, separate forces of directional and stabilizing (or disruptive) selection acting directly on each character can be measured. These directional and stabilizing selection coefficients are respectively the parameters that describe the best linear and quadratic approximations to the selective surface of individual fitness as a function of the phenotypic characters. The theory is illustrated by estimating selective forces on morphological characters influencing survival in pentatomid bugs and in house sparrows during severe weather conditions.
Natural hybridization threatens a substantial number of plant and animal species with extinction, but extinction risk has been difficult to evaluate in the absence of a quantitative assessment of risk factors. We investigated a number of ecological parameters likely to affect extinction risk, through an individual-based model simulating the life cycle of two hybridizing annual plant species. All parameters tested, ranging from population size to variance in pollen-tube growth rates, affected extinction risk. The sensitivity of each parameter varied dramatically across parameter sets, but, overall, the competitive ability, initial frequency, and selfing rate of the native taxon had the strongest effect on extinction. In addition, prezygotic reproductive barriers had a stronger influence on extinction rates than did postzygotic barriers. A stable hybrid zone was possible only when habitat differentiation was included in the model. When there was no habitat differentiation, either one of the parental species or the hybrids eventually displaced the other two taxa. The simulations demonstrated that hybridization is perhaps the most rapidly acting genetic threat to endangered species, with extinction often taking place in less than five generations. The simulation model was also applied to naturally hybridizing species pairs for which considerable genetic and ecological information is available. The predictions from these “worked examples” are in close agreement with observed outcomes and further suggest that an endemic cordgrass species is threatened by hybridization. These simulations provide guidance concerning the kinds of data required to evaluate extinction risk and possible conservation strategies.
Genetic analyses of reproductive barriers represent one of the few methods by which theories of speciation can be tested. However, genetic study is often restricted to model organisms that have short generation times and are easily propagated in the laboratory. Replicate hybrid zones with a diversity of recombinant genotypes of varying age offer increased resolution for genetic mapping experiments and expand the pool of organisms amenable to genetic study. Using 88 markers distributed across 17 chromosomes, we analyze the introgression of chromosomal segments of Helianthus petiolaris into H. annuus in three natural hybrid zones. Introgression was significantly reduced relative to neutral expectations for 26 chromosomal segments, suggesting that each segment contains one or more factors that contribute to isolation. Pollen sterility is significantly associated with 16 of these 26 segments, providing a straightforward explanation of why this subset of blocks is disadvantageous in hybrids. In addition, comparison of rates of introgression across colinear vs. rearranged chromosomes indicates that close to 50% of the barrier to introgression is due to chromosomal rearrangements. These results demonstrate the utility of hybrid zones for identifying factors contributing to isolation and verify the prediction of increased resolution relative to controlled crosses.
Conspicuous differences in floral morphology are partly responsible for reproductive isolation between two sympatric species of monkeyflower because of their effect on visitation of the flowers by different pollinators. Mimulus lewisii flowers are visited primarily by bumblebees, whereas M. cardinalis flowers are visited mostly by hummingbirds. The genetic control of 12 morphological differences between the flowers of M. lewisii and M. cardinalis was explored in a large linkage mapping population of F2 plants (n = 465) to provide an accurate estimate of the number and magnitude of effect of quantitative trait loci (QTLs) governing each character. Between one and six QTLs were identified for each trait. Most (9/12) traits appear to be controlled in part by at least one major QTL explaining ≥25% of the total phenotypic variance. This implies that either single genes of individually large effect or linked clusters of genes with a large cumulative effect can play a role in the evolution of reproductive isolation and speciation.
Up to the end of the 19th century the typological species concept was universally accepted, in which degree of morphological difference was the species criterion. This concept was increasingly replaced (particularly in zoology) beginning around 1900 by the biological species concept because the criterion of morphological distinctness broke down in the case of sibling species and of highly distinct intrapopulational variants. The yardstick for the recognition of biological species is the noninterbreeding of coexisting species in a local situation. This yardstick can be applied to isolated populations only by inference. It is discussed whether the making of such inferences is too arbitrary to be acceptable. A local flora is analyzed to determine whether polyploidy, apomixis, hybridization, and other deviations from regular sexual reproduction are sufficiently frequent in plants to make the biological species concept illusory. It is found that the number of difficulties is small, validating use of the sympatric situation as yardstick for the ranking of allopatric populations.
Gene exchange between locally adapted plant populations can have significant evolutionary consequences, including changes in genetic diversity, introduction of adaptive or maladaptive traits, disruptive of coadaptive gene complexes, and the creation of new ecotypes or even species. The potential for introgression between divergent populations will depend on the strength of selection against nonnative characters. Morphologically variable F2 hybrids of two Gilia capitata subspecies were used to evaluate the strength of phenotypic selection and the response to selection in the home habitats of each subspecies. At both sites, traits diagnostic of the subspecies were subject to significant phenotypic selection, probably mediated by direct selection on unmeasured correlated characters. Phenotypic selection favored native morphologies in all but a single case; leaf shape of one subspecies was favored in both habitats. The strength of selection varied between sites, with one site selecting more strongly against nonnative characters. Offspring of the F2 hybrids showed a significant evolutionary response to selection when grown in a common environment. Evolution was in the direction of similarity with the subspecies native to the site where selection was imposed. This result reveals that native character states are adaptive and suggests that selection will maintain native morphologies even after a substantial influx of genes from an ecologically and morphologically distinct, and locally adapted subspecies.
Models of hybrid zones differ in their assumptions about the relative fitnesses of hybrids and the parental species. These fitness relationships determine the form of selection across the hybrid zone and, along with gene flow, the evolutionary dynamics and eventual outcome of natural hybridization. We measured a component of fitness, export and receipt of pollen in single pollinator visits, for hybrids between the herbaceous plants Ipomopsis aggregata and I. tenuituba and for both parental species. In aviary experiments with captive hummingbirds, hybrid flowers outperformed flowers of both parental species by receiving more pollen on the stigma. Although hummingbirds were more effective at removing pollen from anthers of I. aggregata, hybrid flowers matched both parental species in the amount of pollen exported to stigmas of other flowers. These patterns of pollen transfer led to phenotypic stabilizing selection, during that stage of the life cycle, for a stigma position intermediate between that of the two species and to directional selection for exserted anthers. Pollen transfer between the species was high, with flowers of I. aggregata exporting pollen equally successfully to conspecific and I. tenuituba flowers. Although this study showed that natural hybrids enjoy the highest quality of pollinator visits, a previous study found that I. aggregata receives the highest quantity of pollinator visits. Thus, the relative fitness of hybrids changes over the life cycle. By combining the results of both studies, pollinator-mediated selection in this hybrid zone is predicted to be strong and directional, with hybrid fitness intermediate between that of the parental species.
Abstract Diploid hybrid speciation in plants is often accompanied by rapid ecological divergence between incipient neospecies and their parental taxa. One plausible means by which novel adaptation in hybrid lineages may arise is transgressive segregation, that is, the generation of extreme phenotypes that exceed those of the parental lines. Early generation (BC2) hybrids between two wild, annual sunflowers, Helianthus annuus and Helianthus petiolaris, were used to study directional selection on transgressive characters associated with the origin of Helianthus paradoxus, a diploid hybrid species adapted to extremely saline marshes. The BC2 plants descended from a single F1 hybrid backcrossed toward H. petiolaris. The strength of selection on candidate adaptive traits in the interspecific BC2 was measured in natural H. paradoxus salt marsh habitat. Positive directional selection was detected for leaf succulence and Ca uptake, two traits that are known to be important in salt stress response in plants. Strong negative directional selection operated on uptake of Na and correlated elements. A significant decrease in trait correlations over time was observed in the BC2 population for Na and Ca content, suggesting an adaptive role for increased Ca uptake coupled with increased net exclusion of Na from leaves. Patterns of directional selection in BC2 hybrids were concordant with character expression in the natural hybrid species, H. paradoxus, transplanted into the wild. Moreover, the necessary variation for generating the H. paradoxus phenotype existed only in the BC2 population, but not in samples of the two parental species, H. annuus and H. petiolaris. These results are consistent with the hypothesis that transgressive segregation of elemental uptake and leaf succulence contributed to the origin of salt adaptation in the diploid hybrid species H. paradoxus.
Gli autori hanno condotto un'indagine floristica sulle orchidee presenti nella zona occidentale del Vallo di Diano.Le entità raccolte od osservate nel corso del presente studio ammontano a 49; tra queste Ophrys oxyrrhynchos Tod. subsp. oxyrrhynchos viene segnalata per la prima volta per la penisola, essendo finora nota solo per la Sicilia.L'alto numero di entità ritrovate testimonia una buona naturalità dell'ambiente nell'area indagata; le uniche zone con un basso numero di entità presenti sono quelle situate nelle vicinanze di coltivi e dei centri abitati. Authors carried out a floristic exploration on the orchids present in the Western area of Vallo di Diano (Salerno, Italy). 49 taxa were collected or observed; among these, Ophrys oxyrrhynchos Tod. subsp. oxyrrhynchos is reported for the first time as present in continental Italy (the subspecies was previously reported only from Sicily). The high diversity found is an indication of low anthropization; in fact, the only regions showing a low number of taxa are located near cultivated fields and inurbated areas.
Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears on the screen or printed page of such transmission. The JSTOR Archive is a trusted digital repository providing for long-term preservation and access to leading academic journals and scholarly literature from around the world. The Archive is supported by libraries, scholarly societies, publishers, and foundations. It is an initiative of JSTOR, a not-for-profit organization with a mission to help the scholarly community take advantage of advances in technology. For more information regarding JSTOR, please contact support@jstor.org.
The yardstick for the recognition of biological species is the noninterbreeding of coexisting species in a local situation. This yardstick can be applied to isolated populations only by inference. It is discussed whether the making of such inferences is too arbitrary to be acceptable. A local flora is analyzed to determine whether polyploidy, apomixis, hybridization, and other deviations from regular sexual reproduction are sufficiently frequent in plants to make the biological species concept illusory. The number of difficulties is in fact small, validating use of the sympatric situation as yardstick for the ranking of allopatric populations. -from Author
The Bakersfield saltbush Atriplex tularensis is a salt-tolerant, monoecious annual member of the alkali sink scrub plant community which was once widely distributed in southern San Joaquin Valley, California. The plant has been reduced, by conversion of habitat to agriculture, to a single population at Kern Lake Preserve, about 25 km south of Bakersfield. Seed bank status, soil moisture, germination requirements, and artificial propagation were investigated to determine the most effective strategy for conservation of that remnant population and the associated eccological community. Five seedlings were successfully transferred from the preserve site to greenhouse facilities where they have produced numerous fruits. Phenotypic variation of plants in the field and greenhouse, however, indicates incomplete reproductive isolation between A. tularensis and A. serenana, a widespread, closely related species. The possibility that introgressive hybridization is occurring and its impact on potential conservation strategies are discussed.
Genetic divergence between population samples ofOrchis laxiflora and ofO. palustris from various European locations was studied by electrophoretic analysis of 25 enzyme loci. An average genetic distance of DNei = 1.24 was found between the two taxa, with 12 out of 25 loci showing alternative alleles (diagnostic loci). Genetic heterogeneity was observed within bothO. laxiflora andO. palustris, when northern and southeastern populations were compared, being lower in the former taxon (D = 0.06), than in the latter (D = 0.16). Karyologically, 2n = 36 was found for bothO. laxiflora andO. palustris. O. laxiflora andO. palustris produce hybrids, described asO. ×intermedia. Genotype analysis of several sympatric samples showed the presence of hybrid zones, including F1 hybrids and, in low proportions, recombinant classes, putatively assigned to Fn and backcrosses, as well as a few introgressed individuals of both taxa. These data indicate that hybrids are only partially fertile, with a very limited mixing up of the two parental gene pools; this is also shown by the lack of significant lowering of genetic distances when sympatric and allopatric heterospecific samples are compared. Accordingly,O. laxiflora andO. palustris form a syngameon; nevertheless they can be considered as good taxonomic species, with virtually distinct gene pools, which evolve independently. The genetic variability inO. laxiflora andO. palustris is remarkably low (
e = 0.05 and
e = 0.02, respectively). In particular, nearly complete absence of polymorphic loci was found inO. palustris from northcentral Europe. Two hypotheses are considered to explain the low genetic variability of this endangered species.
When two distinct gene pools meet and produce fertile hybrids, the outcome varies from gene to gene. At some loci a universally favorable allele has been established on one side. Such alleles soon spread through the whole population and hence differences are rarely observed. At other loci different alleles may be favored in different environments or genetic backgrounds; selection maintains these differences in the face of random mixing. At other loci—perhaps at most of those we observe in molecular surveys—different alleles may have been established by chance and may have no appreciable effect on fitness. These differences gradually fade away, at a rate that depends on the strength of selection against introgression at the other loci with which they are associated.
Pinus evolved in middle latitudes of the Northern Hemisphere in the middle Mesozoic. By the late Cretaceous pines had spread east and west throughout Laurasia, attaining high diversity in eastern Asia, the eastern United States, and western Europe, but having little representation at high northern latitudes. Changing climates in the early Tertiary established warm and humid tropical/subtropical conditions in a broad zone to 70-degrees-N throughout middle latitudes. Pines and their relatives disappeared from many middle-latitude areas during this time and were replaced by diverse angiosperm taxa of the boreotropical flora, which were adapted to the equable, tropical climate. The effect of this climate change and spread of boreotropical flora was to displace pines from their former habitats. A hypothesis is defended that pines shifted, during the three warm periods of the Eocene, into three major refugial areas in the Northern Hemisphere: high latitudes, low latitudes, and upland regions of middle latitudes, especially in western North America. Some of these refugial areas (e.g., Mexico/Central America) underwent active volcanism and mountain-building in the Eocene and became secondary centers of pine diversity. Many phylogenetic patterns within Pinus can be traced to this fragmentation, isolation, and evolution in Eocene refugia. Subsections Oocarpae and Sabinianae appear to have originated from refugia in Mexico and Central America. Older subsections such as Sylvestres, Ponderosae, Contortae, and Strobi were distributed over several refugia; subsections Leiophyllae, Australes, and Cembroides evolved in southern refugia in North America; and Canarienses evolved in southern refugia along the Tethys seaway in Eurasia. Following the cooling and drying of the climate at the end of the Eocene, many angiosperm taxa of the boreotropical flora became extinct and pines recolonized middle latitudes, a zone they have occupied to the present. Migration out of refugia provided additional opportunities for hybridization and introgression, as formerly isolated lineages expanded and met.
Selection experiments in the wild have greatly aided our understanding of how selection shapes phenotypic diversity in natural populations. However, these experi- ments have been hindered by the fact that the traits most important to adaptation and speciation may be fixed within populations. Experimental hybridization offers a means to circumvent this problem since crosses can be made between populations or species that differ for the trait of interest. Here, we discuss the advantages and limitations of this approach, review results from published studies, and suggest strategies for future experi- ments. Advantages associated with this approach include the ability to ''generate'' variation for traits of interest, as well as the increased sensitivity of selection assays because of the wider range of trait values characteristic of segregating hybrids. Moreover, experimental hybridization can be extended to crosses between near-isogenic lines, allowing the effects of major quantitative trait loci (QTLs) to be dissected in a well-defined genetic background. Limitations include widespread linkage disequilibrium created by hybridization, possible cosegregation of hybrid incompatibilities, and the large number of variable traits likely to affect hybrid fitnesses. Even with these limitations, this basic approach has been remarkably successful. We now know, for example, that many morphological differences between divergent populations or species are under selection and that the selection gradients may be surprisingly large. Also, small genetic changes in premating barriers may have large effects on assortative mating. With respect to discussions about the role of hybridization in evolution, experiments indicate that some hybrid trait combinations may be advantageous, particularly when the hybrid populations are placed in a new environment. Future studies seem likely to combine selection measurements with genetic mapping of the QTLs under- lying the selected traits. Natural hybrid zones hold particular promise for these kinds of studies because the only experimental manipulation required is the removal of small amounts of tissue for genotyping.
Models of hybrid zones differ in their assumptions about the relative fitnesses of hybrids and the parental species. These fitness relationships determine the form of selection across the hybrid zone and, along with gene flow, the evolutionary dynamics and eventual outcome of natural hybridization. We measured a component of Fitness, export and receipt of pollen in single pollinator visits, for hybrids between the herbaceous plants Ipomopsis aggregata and I. tenuituba and for both parental species. In aviary experiments with captive hummingbirds, hybrid flowers outperformed flowers of both parental species by receiving more pollen on the stigma. Although hummingbirds were more effective at removing pollen from anthers of I. aggregata, hybrid flowers matched both parental species in the amount of pollen exported to stigmas of other flowers. These patterns of pollen transfer led to phenotypic stabilizing selection, during that stage of the life cycle, for a stigma position intermediate between that of the two species and to directional selection for exserted anthers. Pollen transfer between the species was high, with flowers of I. aggregata exporting pollen equally successfully to conspecific and I. tenuituba flowers. Although this study showed that natural hybrids enjoy the highest quality of pollinator visits, a previous study found that I. aggregata receives the highest quantity of pollinator visits. Thus, the relative fitness of hybrids changes over the life cycle. By combining the results of both studies, pollinator-mediated selection in this hybrid zone is predicted to be strong and directional, with hybrid fitness intermediate between that of the parental species.
Hybrid zones are narrow regions in which genetically distinct populations meet, mate and produce hybrids; they are often only a few hundred meters wide yet may be several hundred kilometers long. After a clarification of terminology, the authors summarise relevant theory (maintenance of clines, movement of hybrid zones, barriers to gene flow, and modification of hybrid zones). They then describe ways in which this can be used to draw inferences from field data, with consideration of whether dispersal maintains hybrid populations; the strength and model of selection in the balance between dispersal and selection; the nature and implications of primary and secondary contact; the significance of reproductive isolation and introgressions; the increase of rare alleles in hybrid zones; the number and types of genes involved in hybrid zones; and evidence for modification of hybrid zones. The characteristic spatial configuration of most hybrid zones and the wide range of genotypes found within them suggest that the great majority are maintained in a stable balance between dispersal and selection. -P.J.Jarvis
Two European species belong to the genus Zelkova: Z. abelicea Boisser, endemic to the island of Crete, and Z. sicula Di Pasquale, Garfı̀ and Quézel, endemic to Sicily. Nuclear DNA markers (ISSR and AFLP) were analysed in the two species. Results showed genetic variation within the Z. abelicea population but not within the Z. sicula population. This species, existing as a unique population, revealed to be represented by a unique genotype, which is not present in the Z. abelicea sampling, thus indicating that an extreme reduction of genetic variability characterises Z. sicula. Based on this result, we can assume that agamic propagation is the reproductive strategy of this species in its present environment, unfavourable to the development of regular and functional flowering structures. The priorities for conservation programs are discussed in the light of the different genetic resources represented by the two taxa.
Abstract A previous study of the hybrid zone in western Panama between white-collared (Manacus candei) and golden-collared manakins (M. vitellinus) documented the unidirectional introgression of vitellinus male secondary sexual traits across the zone. Here, we examine the hybrid zone in greater genetic and morphological detail. Statistical comparisons of clines are performed using maximum-likelihood and nonparametric bootstrap methods. Our results demonstrate that an array of six molecular and two morphometric markers agree in cline position and width. Clines for male collar and belly color are similar in width to the first eight clines, but are shifted in position by at least five cline widths. The result is that birds in intervening populations are genetically and morphometrically very like parental candei, but males have the plumage color of parental vitellinus. Neither neutral diffusion nor nonlinearity of color scales appear to be viable explanations for the large cline shifts. Genetic dominance of vitellinus plumage traits is another potential explanation that will require breeding experiments to test. Sexual selection remains a plausible explanation for the observed introgression of vitellinus color traits in these highly dimorphic, polygynous, lek-mating birds. Two other clines, including a nondiagnostic isozyme locus, are similar in position to the main cluster of clines, but are broader in width. Thus, introgression at some loci is greater than that detected with diagnostic markers. Assuming that narrow clines are maintained by selection, variation in cline width indicates that selection is not uniform throughout the genome and that diagnostic markers are under more intense selective pressure. The traditional focus on diagnostic markers in studies of hybrid zones may therefore lead to underestimates of average introgression. This effect may be more pronounced in organisms with low levels of genetic divergence between hybridizing taxa.
Most studies of plant hybridization are concerned with documenting its occurrence in different plant groups. Although these descriptive, historical studies are important, the majority of recent advances in our understanding of the process of hybridization are derived from a growing body of experimental microevolutionary studies. Analyses of artificially synthesized hybrids in the laboratory or glasshouse have demonstrated the importance of gametic selection as a prezygotic isolating barrier; the complex genetic basis of hybrid sterility, inviability and breakdown; and the critical role of fertility selection in hybrid speciation. Experimental manipulations of natural hybrid zones have provided critical information that cannot be obtained in the glasshouse, such as the evolutionary conditions under which hybrid zones are formed and the effects of habitat and pollinator‐mediated selection on hybrid‐zone structure and dynamics. Experimental studies also have contributed to a better understanding of the biology of different classes of hybrids. Analyses of morphological character expression, for example, have revealed transgressive segregation in the majority of later‐generation hybrids. Other studies have documented a high degree of variability in fitness among different hybrid genotypes and the rapid response of such fitness to selection – evidence that hybridization need not be an evolutionary dead end. However, a full accounting of the role of hybridization in adaptive evolution and speciation will probably require the integration of experimental and historical approaches.
CONTENTS
Summary
599
I.
Introduction
599
II.
Concepts and terminology
600
III.
Historical background
600
IV.
Studies of experimental hybrids
601
V.
Experimental manipulations of natural hybrid populations
609
VI.
The biology of different classes of hybrids
612
VII.
Conclusions and future research
619
Acknowledgements
620
References
620
Taxa endemic to North-western Europe are rare, but the orchid genusDactylorhiza contains several species restricted to this area. Evidence from morphological and cytological studies have indicated that some species may have arisen recently and may be of hybrid origin. In the present report, I use allozymes to characterize the genomes in various species ofDactylorhiza and evaluate the possibilities for rapid evolutionary change in the genus. Allotetraploid species have evolved repeatedly from two principal diploid ancestral lineages. These lineages include extant diploid and autotetraploid species, from which allotetraploid derivatives may still arise. It is suggested that allotetraploidization dominates over introgression as speciation mechanism in the genus. The more common and widespread allotetraploid species could be characterized by their allozyme characters over considerable distances, indicating that each of them may have a unique origin and that they have spread from their ancestral populations to the present distribution areas. However, it is also possible that some allotetraploid species contain local populations that have been independently derived from the ancestral lineages.
The localized hybridization between Orchis mascula and O. provincialis in Sardinia is investigated. The two parental species are closely related and share the same pollinators but do not hybridize in any other areas of sympatry. Artificial crosses between the two species in areas of sympatry on the continent revealed that, in absence of an ethological isolation, a strong post-pollination barrier exists and preserves species integrity in the main part of their distribution. However, on Sardinia, morphological observations, karyological and molecular analyses of intermediate phenotypes confirmed the occurrence of hybridization between the insular O. mascula ssp. ichnusae and O. provincialis and the bi-directionality of pollen flow. The occurrence of hybrids on the island indicates a failure of otherwise strong post-pollination barriers between O. mascula and O. provincialis.
A small population (16 individuals) of Orchis colemanii Cortesi, a natural hybrid between O. mascula (L.) L. and O. pauciflora Ten. was sampled from a locality near Sassano (National Park of Cilento, province of Salerno, Southern Italy) in order to assess its genetic structure. Filter hybridizations of O. colemanii, O. mascula and O. pauciflora DNAs against a PCR-amplified ribosomal fragment indicated that all the hybrid individuals in study have the ribosomal repeats of both parents, even if not always combined in equal proportions, and that no specimen morphologically identified as O. mascula or O. pauciflora possessed detectable rDNA of the other species. The majority of the hybrid specimens (12 individuals) showed a preponderance of O. mascula rDNA, three had approximately equal proportions of parental repeats and one had a preponderance of O. pauciflora rDNA. As the parental species have different amounts of rDNA, as inferred from dot blot hybridization, it has been deduced that the 12 specimens may represent F1 or successive, presumably non-recombinant progenies, while the last four specimens may represent either F2 genotypes or backcrosses with O. pauciflora.
Flowers of different species that resemble each other are not necessarily mimics. For mimicry to be occurring, the similarity must be adaptive. Unfortunately, no case of floral mimicry has ever been fully verified and it is important that we move beyond these perceived similarities to testing whether they are truly adaptive. Here we explain the differences between Batesian and Müllerian floral mimicry, illustrate what should be done to test mimicry hypotheses, and discuss how interspecific pollen transfer influences the evolution of mimicry.
Polyploidy has played a major role in the evolution of many eukaryotes. Recent studies have dramatically reshaped views of polyploid evolution, demonstrating that most polyploid species examined, both plant and animal, have formed recurrently from different populations of their progenitors. Populations of independent origin can subsequently come into contact and hybridize, generating new genotypes. Because of the frequency of polyploidy in plants, many recognized species are probably polyphyletic. Extensive and rapid genome restructuring can occur after polyploidization. Such changes can be mediated by transposons. Polyploidization could represent a period of transilience, during which genomic changes occur, potentially producing new gene complexes and facilitating rapid evolution.
The origin of new homoploid species via hybridization is theoretically difficult be- cause it requires the development of reproductive isolation in sympatry. Nonethe- less, this mode is often and carelessly used by botanists to account for the for- mation of species that are morphologically intermediate with respect to related congeners. Here, I review experimental, theoretical, and empirical studies of homoploid hybrid speciation to evaluate the feasibility, tempo, and frequency of this mode. Theoretical models, simulation studies, and experimental syntheses of stabilized hybrid neospecies indicate that it is feasible, although evolution- ary conditions are stringent. Hybrid speciation appears to be promoted by rapid chromosomal evolution and the availability of a suitable hybrid habitat. A selfing breeding system may enhance establishment of hybrid species, but this advantage appears to be counterbalanced by lower rates of natural hybridization among self- ing taxa. Simulation studies and crossing experiments also suggest that hybrid speciation can be rapid—a prediction confirmed by the congruence observed be- tween the genomes of early generation hybrids and ancient hybrid species. The frequency of this mode is less clear. Only eight natural examples in plants have been rigorously documented, suggesting that it may be rare. However, hybridiza- tion rates are highest in small or peripheral populations, and hybridization may be important as a stimulus for the genetic or chromosomal reorganization envisioned in founder effect and saltational models of speciation.
