Taxonomy of Cyrtochilum-alliance (Orchidaceae) in the light of molecular and morphological data

Abstract

BackgroundThe generic separateness and specific composition of the orchid genus Cyrtochilum was discussed for almost two centuries. Over the years several smaller taxa were segregated from this taxon, but their separateness was recently questioned based on molecular studies outcomes. The aim of our study was to revise concepts of morphological-based generic delimitation in Cyrtochilum-alliance and to compare it with the results of genetic analysis. We used phylogenetic framework in combination with phenetical analysis to provide proposal of the generic delimitation within Cyrtochilum-alliance. Two molecular markers, ITS and matK were used to construct phylogenetic tree. A total of over 5000 herbarium specimens were included in the morphological examination and the phenetical analysis included 29 generative and vegetative characters.ResultsComparative morphology of the previously recognized genera: Buesiella, Dasyglossum, Neodryas, Rusbyella, Siederella and Trigonochilum is presented. A new species within the the latter genus is described. Fourteen new combinations are proposed. The key to the identification of the genera of the Cyrtochilum-alliance and morphological characteristics of each genus are provided.ConclusionsA total of six separated genera are recognized within Cyrtochilum-alliance. The reasons of the incompatibility between morphological differences observed within studied taxa and phylogenetic tree are argued and the taxonomic implications of such inconsistency, resulting in fragmentation or lumping of taxonomic units, are discussed.Electronic supplementary materialThe online version of this article (doi:10.1186/s40529-017-0164-z) contains supplementary material, which is available to authorized users.

Towards a taxonomic revision of the genusCyrtochilum(Orchidaceae) in Northwestern South America (Northern Peru, Ecuador, Colombia, Venezuela)

“…Neodryas and Rusbyella can be distinguished based on the gynostemium and the lip form-digitate projections on each sides of the stigma are observed in Neodryas (vs very obscure projections or no projections in Rusbyella) the lip of which is sessile (long-clawed in Rusbyella). This topic was previously discussed in details by Szlachetko et al (2017).…”

“…Cyrtochilum s.str. can be distinguished from all the genera recognised by Szlachetko et al (2017) based on the angle between the lip and gynostemium (more or less right angle in Siederella, Cyrtochilum and Trigonochilum, gynostemium parallel with the lower part of the lip in Dasyglossum, Neodryas and Rusbyella) as well as based on lip form (lip unguiculate and larger than tepals in Siederella, sessile and much smaller than tepals in Cyrtochilum s.str.). While the lip of small-flowered representatives of Trigonochilum is triangular-cordate in outline, the lip of Cyrtochilum s.str.…”

The origin of Humboldt and Bonpland's holotype of Oncidium ornithorhynchum, clarified using +200‐year‐old DNA

“…The phylogenetic tree presented by Neubig & al. () has raised several debates (e.g., Dalström & Higgins, ; Kolanowska & Szlachetko, ; Szlachetko & al., ) as many of the groups that were morphologically defined in the past did not form monophyletic clades, indicating the need of new classifications (Dalström, ). In the case of the Heteranthocidium clade, a reconsideration of the traditional concept (sensu Szlachetko & al., ) was proposed in accordance to Neubig & al.…”

A new small-flowered Cyrtochilum species (Orchidaceae: Oncidiinae) from the Condor mountains in Ecuador

“…To include some complexes of plants that molecular evidence show belong together in a monophyletic Cyrtochilum (Williams et al 2001, Pridgeon et al 2009 et al 2017) for example, but exclude the closely related C. pardinum Lindl., and C. ramosissimum (Lindl.) Dalström complexes, which also belong in the same monophyletic Cyrtochilum, and move them into the distantly related Odontoglossum based on floral similarities alone (Szlachetko et al 2017) is inconsistent with the principles of monophyletic genera and is not accepted by us. We, therefore, prefer to maintain Cyrtochilum as circumscribed by Dalström (2001), by Williams et al (2001), and by Pridgeon et al (2009) DiagnoSiS: Cyrtochilum gentryi is distinguished from all other small-flowered Cyrtochilum species by the combination of features such as a creeping habit similar to species in the C. undulatum, C. flexuosum and C. auropurpureum (Rchb.f.)…”

“…With time, however, many new species were discovered and described, and it became more and more difficult to delineate Cyrtochilum from particularly Oncidium and Odontoglossum Kunth (Lindley 1833). As a result, a considerable confusion and disagreement developed among taxonomists how to treat this large group of plants (Lindley 1838, 1841, 1852, 1855, Reichenbach 1849, Beer 1854, Rolfe 1896,Kränzlin 1917,1922, Schlechter 1924, Garay 1970, Bockemühl 1989, Königer 1991, 1996, Königer & Schildhauer 1994, Senghas 1994, 1997, Dalström 2001, Szlachetko et al 2017, which continue to this day. Part of the reason for this controversy is the natural variation of species within this large complex of plants, and partially depending on the taxonomists' preference for large or small genera and specifically what features to base them on.…”