Epipactis × subtilis (Orchidaceae), a New Hybrid between E. albensis and E. purpurata
Abstract
A new natural hybrid Epipactis ×subtilis Jakubska-Busse, Żołubak & Łobas, hybr. nat. nov. (Epipactis albensis × Epipactis purpurata) was described and documented from the province of Lower Silesia (SW Poland). The hybrid's morphological characteristics are compared with those of the parental species.
... The currently adopted classification system of Epipactis does not take sufficient account of the variation range of morphological characters within its taxa, nor does it explain the underlying sources of this variability. Moreover, the species delimitation within Epipactis is often complicated by the ease with which the interspecific hybrids are formed in the locations inside the native ranges of the parental species, the existence of which is a common cause of taxa misidentification [15][16][17][18][19][20][21]. The fluidity of the morphological boundaries between various Epipactis species causes serious difficulties in determinig the diagnostic characters useful in species identification [22][23][24]. ...
The Epipactis helleborine (L.) Crantz group is one of the most taxonomically challenging species complexes within the genus Epipactis. Because of the exceptionally high levels of morphological variability and the ability to readily cross with other species, ninety different taxa at various taxonomic ranks have already been described within its nominative subspecies, but the taxonomic status of most of them is uncertain, widely disputed, and sometimes even irrelevant. The present review is based on results of the most recent research devoted to the E. helleborine group taxonomy. In addition, we analysed data about taxa belonging to this group presented in some research articles and monographs devoted directly to the genus Epipactis or to orchids in certain area(s). Based on the reviewed literature and data collected in four taxonomic databases available online, we propose an updated list of the 10 currently accepted taxa in the E. helleborine group (two species, six subspecies, and two varieties), which includes E. helleborine (L.) Crantz subsp. helleborine; E. helleborine subsp. bithynica (Robatsch) Kreutz; E. helleborine subsp. distans (Arv.-Touv.) R.Engel and P.Quentin; E. helleborine subsp. neerlandica (Verm.) Buttler; E. helleborine var. tangutica (Schltr.) S.C.Chen and G.H.Zhu; E. helleborine subsp. tremolsii (Pau) E.Klein; E. helleborine subsp. voethii (Robatsch) Jakubska-Busse, Żołubak, and Łobas, stat. nov.; E. condensata Boiss. ex D.P.Young; E. condensata var. kuenkeleana (Akhalk., H.Baumann, R.Lorenz, and Mosul.) Popovich; and E. cupaniana C.Brullo, D’Emerico, and Pulv.
... Nonetheless, hybrids between bona fide species within section Epipactis are often reported in nature (Vlčko et al., 2003;Batoušek, 2010). The limited genetic evidence of gene flow between species reliably indicates flow from allogams (typically E. helleborine) into autogams, including E. dunensis tynensis and E. phyllanthes (Hollingsworth et al., 2006), but such hybridization has also been inferred through morphological means in the case of E. purpurata × albensis (Jakubska-Busse et al., 2017). ...
Background and aims:
The terrestrial orchid genus Epipactis has become a model system for the study of speciation via transitions from allogamy to autogamy, but close phylogenetic relationships have proven difficult to resolve through Sanger sequencing.
Methods:
We analysed with RAD-seq 108 plants representing 29 named taxa that together span the genus, focusing on section Epipactis. Our filtered matrix of 12,543 single nucleotide polymorphisms was used to generate an unrooted network and a rooted, well-supported likelihood tree. We further inferred genetic structure through a co-ancestry heat-map and admixture analysis, and estimated inbreeding coefficients per sample.
Key results:
The 27 named taxa of the ingroup were resolved as 11 genuine, geographically widespread species: four dominantly allogamous and seven dominantly autogamous. A single comparatively allogamous species, E. helleborine, is the direct ancestor of most of the remaining species, though one of the derived autogams has generated one further autogamous species. An assessment of shared ancestry suggested only sporadic hybridisation between the re-circumscribed species. Taxa with greatest inclination towards autogamy show less if any admixture, whereas the gene pools of more allogamous species contain a mixture alleles found in the autogams.
Conclusions:
This clade is presently undergoing an evolutionary radiation driven by a wide spectrum of genotypic, phenotypic and environmental factors. Epipactishelleborine has also frequently generated many local variants showing inclinations toward autogamy (and occasionally cleistogamy) best viewed as incipient speciation from within the genetic background provided by Epipactis helleborine, which thus becomes an example of a convincingly paraphyletic species. Autogams are often as widespread and ecologically successful as allogams.
... However, despite these exquisite barriers that prevent invasion of the genome from one species to another, natural hybrids are quite common and have continuously been discovering in every main lineage of this family (e.g. Iamonico et al. 2011;Jakubska-Busse et al. 2017;Lee 2013;Liu & Chen 2007;Neto et al. 2012;Nielsen 2000). ...
Several species in the genus Pleione (Orchidaceae) have same or overlapping geographical distribution in China. In this study, two new natural hybrids, Pleione × baoshanensis and Pleione × maoershanensis, were described and illustrated. The parentage for these two hybrids was confirmed using molecular data from ITS of the nuclear ribosomal, trnT-trnL spacer and trnL-trnF region (trnL intron and trnL-trnF spacer) of the plastid DNA. Pleione × baoshanensis is intermediate between P. albiflora and P. yunnanensis, and characterized by its erose lamellae on the lip. Meanwhile, Pleione × maoershanensis is intermediate between P. hookeriana (P. chunii) and P. pleionoides, and characterized by its deep lacerate lamellae on the lip. For the individuals tested, molecular data suggest that P. albiflora is the maternal parent of Pleione × baoshanensis, and P. hookeriana (P. chunii) is the maternal parent of Pleione × maoershanensis. The history and taxonomic status of P. chunii is also discussed.
A wide range of phenotypic variability in the orchid Epipactis purpurata s. stricto was found based on analysis of herbarium material and field research. Twenty-three biometric features were analysed. New diagnostically important features of gynostemium as well as of petal and sepal sizes and colours were established. Thus E.purpurata s. stricto is redescribed, clarifying the taxonomic importance of several morphological features.
Leaf undulation is used as a diagnostic feature in the taxonomy of different taxa of the Epipactis (Orchidaceae) genus. It is considered a specifically important trait, apart from the column (gynostemium) structure, in the identification of E. muelleri. However, leaf undulation is a common developmental phenomenon in various plants, including orchids, thus the main goal of the research presented was to validate the usefulness of this feature in Epipactis taxonomy.
In the course of this study, the leaf structure of six Epipactis species was analyzed, i.e. E. albensis, E. atrorubens, E. helleborine, E. muelleri, E. palustris, and E. purpurata. The leaf margin outline and the cellular pattern of the leaf surface, as well as the presence of papillae, were examined in detail. The results obtained showed that in all taxa analyzed, representing different groups of the Epipactis genus, leaf undulation was present. The phenomenon was related to leaf-blade development and the local differential growth of leaf sectors rather than to the taxonomic position of the species. Therefore, leaf undulation studied in Helleborines, does not have a diagnostic value as a non-programmed intrinsic feature, and should not be applied to the taxa identification. The valid trait in Epipactis classification (including E. muelleri) remains the column structure.
Fossil leaves of two Early Miocene orchids (Dendrobium and Earina) are reported from New Zealand. The distinctive, raised tetra- to cyclocytic stomatal subsidiary cells of Earina and characteristic papilla-like absorbing glands and "ringed" guard cells of Dendrobium support the placement of the fossils into these genera. These therefore represent the first Orchidaceae macrofossils with cuticular preservation, the oldest records for subfamily Epidendroideae, as well as the first New Zealand and southern hemisphere fossil records for Orchidaceae. These taxa belong in basal clades to the Vandeae/Cymbideae or Epidendreae (Earina) and the Australasian clade of Dendrobium sensu lato. This phylogenetic placement demonstrates expansion of epiphytic orchids into Zealandia by the mid-Cenozoic and an important role for southern continents in the diversification of Orchidaceae.