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

Abstract

Background: The 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.

Results: Comparative 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.

Conclusions: A 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.

Keywords: Cyrtochilum; Monophyly; New combinations; New species; Oncidiinae; Paraphyly; Taxonomy.

Fig. 1

Cyrtochilum volubile. a Gynostemium, side view. b Gynostemium, bottom view. c Anther. d Pollinia, various views. e Tegula and viscidium, various views (Szlachetko & Mytnik-Ejsmont 2009)

Fig. 2

Phenetic similarity (UPGMA) of Cyrtochilum s.l. species based on morphological data

Fig. 3

Bayesian 50% majority-rule tree for genus Cyrtochilum from ITS1-5.8S-ITS2 sequences. The numbers below the branches are bootstrap percentages (BP) and posterior probability (PP), bootstrap percentages ≥50% are given for supported clades. The branches length is shown above

Fig. 4

Majority-rule consensus of 7500 trees obtained in Bayesian analysis of matK gene for genus Cyrtochilum. Values below branches represent bootstrap support (≥50%) from 1000 replicates and posteriori probabilities (≥50%) (BP/PP). The branches length is shown above

Fig. 5

Cyrtochilum cryptocopis. Photo: Guido Deburghgraeve

Fig. 6

Odontoglossum angustatum. Photo by Guido Deburghgraeve

Fig. 7

Odontoglossum epidendroides. Photo by Guido Deburghgraeve

Fig. 8

Odontoglossum odoratum. a Gynostemium, side view. b Gynostemium, bottom view. c Rostellum, side view. d Anther. e Pollinia, various views (Szlachetko & Mytnik-Ejsmont 2009).

Fig. 9

Dasyglossum myanthum. Photo: Guido Deburghgraeve

Fig. 10

Dasyglossum myanthum. a Gynostemium, bottom view. b Gynostemium, side view. c Anther. d Pollinia, various views. e Tegula and viscidium, various views (Szlachetko & Mytnik-Ejsmont 2009)

Fig. 11

Trigonochilum meirax. Photo: Guido Deburghgraeve

Fig. 12

Trigonochilum meirax. a Gynostemium, bottom view. b Gynostemium, side view. c Anther. d Pollinia, various views. e Tegula and viscidium (Szlachetko & Mytnik-Ejsmont 2009)

Fig. 13

Rusbyella aurantiaca. Photo: Guido Deburghgraeve

Fig. 14

Neodryas rhodoneura. Photo: Eric Hunt

Fig. 15

Neodryas schildhaueri. Photo: Guido Deburghgraeve

Fig. 16

Siederella aurea. a, b Lip, c, d lateral sepals, e gynostemium. Drawn by N. Olędrzyńska. Scale bar 5 mm

Fig. 17

Siederella aurea. Photo: Guido Deburghgraeve

Fig. 18

Siederella aurea. a Gynostemium, bottom view. b Gynostemium, side view. c Anther. d Pollinia, various views (Szlachetko & Mytnik-Ejsmont 2009)

Fig. 19

Oncidium loxense. a Lip, b lateral sepals, c lip. Drawn by N. Olędrzyńska. Scale bar a, b = 10 mm, c = 5 mm

Fig. 20

Oncidium loxense. Photo: Eric Hunt

Fig. 21

Cyrtoglossum flowers. Photos provided by Ecuagenera

Fig. 22

Cyrtochilum volubile. a, b Lip, c lateral sepals, d gynostemium. Drawn by N. Olędrzyńska. Scale bar 5 mm

Fig. 23

Trigonochilum koenigerii—dissected perianth. a Dorsal sepal, b petal, c lateral sepal, d lip. Drawn by S. Nowak from the holotype

Fig. 24

Trigonochilum koenigerii. a Flower (side view), b gynostemium, c flower (front view), d fragment of the inflorescence. Photos: R. Medina