In Search of the True Pleurothallis
By Dr. Alec M. Pridgeon - England


For two centuries orchid taxonomists have known that Pleurothallis is an artificial assemblage with no morphological characters that can be used to define and distinguish it from many other genera of subtribe Pleurothallidinae. Until the advent of the use of DNA sequences in plant systematics there was no reliable way to understand genetic relationships under the broad umbrella of Pleurothallis. Ongoing phylogenetic studies using sequences from three different gene regions have pointed the way toward a reproducible and well-supported restructuring of this artficial megagenus into as many as eight groups. Generic names were already available for all of them, reflecting relationships correctly identified by many taxonomists of the past and present. With a genetic foundation for Pleurothallis and its relatives now in place, we can begin to address questions about character evolution and biogeography of the subtribe for the first time.

Dr. Alec M. Pridgeon is Sainsbury Orchid Fellow of the Royal Botanic Gardens, Kew, and co-editor of Genera Orchidacearum, a comprehensive multi-volume monograph of the orchid family. In orchid circles he is perhaps best known as past editor of the American Orchid Society Bulletin (now titled Orchids), Lindleyana, and The Illustrated Encyclopedia of Orchids.



Classification of Bulbophyllum based on molecular and morphological data
By Barbara Gravendeel


National Herbarium Nederland, Universiteit Leiden Branch - The Netherlands
Of the pantropical genus Bulbophyllum Thouars ca. 1200 species have been described. The name is derived from the Latin word “bulbus”, which means shaped like a bulb and the Greek word “phullon” which means leaf and which refers to the spherical shaped pseudobulbs on top of which the leaf or leaves are implanted. Other diagnostic characters by which the genus is easily recognised are the single-noded pseudobulbs, basal inflorescences and mobile lip.
Bulbophyllum has undergone a tremendous radiation in additional vegetative and floral characters: inflorescences can be compound or simple, with few to many, spirally or distichously arranged flowers. Sepals and petals can be straight or reflexed, sessile or clawed, and are often adorned with hairs, callosities and other appendages. The anther can have either two or four pollinia with or without a stipe. Most species of Bulbophyllum are epiphytes and grow in misty montane forests at 1000-2500 m altitude or in kerangas forests on wet, leached sandy soils.
A good homology assessment of the large amount of different states of morphological characters is often not possible. Therefore, a DNA sequence based study was carried out to reconstruct a phylogenetically based subdivision of Bulbophyllum and allies. The questions I want to answer with this phylogeny are focussed on biogeography and taxonomy. I am interested in (1) where the Bulbophyllinae originated (Asia, Africa, Madagascar or South America) and (2) when this happened (before or after Eocene climatological coolings). In addition, I want to investigate (3) whether separate genera in the Bulbophyllinae (such as Drymoda, Pedilochilus, Sunipia and Trias) are representing independent evolutionary units and 4) whether sections of Bulbophyllum with controversial taxonomic status (such as Cirrhopetalum) deserve generic status as some taxonomists (Lindley, Garay) claim but others (Reichenbach f., J.J. Smith, Seidenfaden, Vermeulen) dispute.

Dr. Barbara Gravendeel obtained her PhD in 2000 with a study on the morphological and molecular systematics of Coelogyne at the Nationaal Herbarium Nederland - Leiden University branch. As a postdoc, she performed parentage analyses of natural hybrids in Pleione and biogeographical analyses of the Coelogyninae. Currently, she is employed by the Dutch Science Foundation to reconstruct the phylogeny of Bulbophyllum and investigate the molecular basis of its anther morphology.

Aerides (Orchidaceae): Molecular Phylogenetics and Floral Morphology
By Alexander Kocyan (1), Ed F. de Vogel (2), Elena Conti (3), Barbara Gravendeel (4)


The orchid genus Aerides comprises 19 epiphytic or lithophytic species ranging from the Himalayas all over South East Asia. Sequences of one nuclear (ITS) and two chloroplast markers (matK, trnL-F) of 14 Aerides and 13 outgroup taxa were generated to reconstruct phylogenetic relationships within the genus. Analysis of chloroplast marker sequences revealed that Aerides is monophyletic. However, topology among Aerides species contradicts the classification at the sectional level by Christenson (1987) based on morphological characters. Multiple copies of the ITS regions were identified, suggesting incomplete homogenization of the ribosomal repeat units or a hybrid origin of some species. Floral development of Aerides differs slightly from the normal monandrous orchid pattern as the abaxial sepal appears before the abaxial petals (Aerides krabiensis) or more or less simultaneously with them, whereas usually the abaxial petals appear before the abaxial sepal. Ovary development is initiated during the bending of the anther. First developmental stages show a non-differentiated bag-like structure. Soon after, the ovary becomes structured. In the mature flower, the ovary is unilocular containing thousands of ovules that are developmentally halted at an early stage. At anthesis, most Aerides species show a more or less prominent 'Saftdecke' or 'nectar cover' in the spur base. This structure may be a protection against raindrops, evaporation or nectar thieves. One clade is characterized by the loss of this character.

(1) Dr. Alexander Kocyan works as a Post-doctoral Research Assistant at the Institute of Systematic Botany of the University of Munich. For his PhD-thesis 2001 he studied the floral morphology of apostasioid orchids at the University of Zurich. He also stayed as a research post-doc researcher in Leiden and Zurich.
(2) Nationaal Herbarium Nederland, Universiteit Leiden Branch, The Netherlands
(3) Institute of Systematic Botany, University of Zurich- Zurich, Switzerland
(4) Institute of Systematic Botany, Ludwig-Maximilians-University Munich

Classification of Pleurothallidinae
Dr. Rodolfo Solano Gómez - Herbario AMO, Mexico D.F. Mexico

Recently the Pleurothallidinae classification had been changed according to the results of a molecular phylogeny. Nevertheless, several of these changes were based on poorly sampled groups and are unknown the morphological apomorphies for these, therefore this phylogenetic classification had not been broadly accepted and most authors still use the systematic classification. However, the later is mainly based on floral characters, which are homoplasic and seem be of reduce utility to infer the relationships among the genera. Although the information obtained from anatomy, palynology and vegetative morphology is not yet adequately integrate in the Pleurothallidinae taxonomy, this can be useful for the phylogeny of the group. This kind of data, in addition of those from DNA sequences, are include in a total evidence analysis for Pleurothallidinae, in which is extended the sampling in some genera with a confused delimitation (sensu Pridgeon & Chase) such as Anathallis, Pleurothallis, Specklinia and Stelis. Also, this study allow provide a more useful classification system and the apomorphies for the recognition of the genera.

Dr Rodolfo Solano Gómez was born in 1968, in Mexico City. He studied biology in the Universidad Nacional Autónoma de México and gots his Ph.D. in the same institution. He worked from several years as associate researcher in the AMO Herbarium, with Miguel Soto Arenas and Eric Hagsater. Now he lives in the Oaxaca City, where he is a researcher for the Instituto Politécnico Nacional and is studing the Oaxacan orchids. His main orchids interests are the systematics of Pleurothallidinae subtribe and the taxonomy and conservation of Mexican orchids. Since several years ago has been preparing the taxonomic review to the Mexican species. He was a coauthor with Alec Pridgeon and Mark Chase in the molecular phylogeny of Pleurothallidinae and now he's preparing the molecular phylogeny of Stelis sensu lato".

Diversification of life forms and mycorrhizal relationships in Cymbidium: insights from molecular and anatomical data
By Tomohisa Yukawa, Kazumitsu Miyoshi, Jun Yokoyama, and William L. Stern


Cymbidium Sw., an orchid genus distributed from East and Southeast Asia to Australia, comprises about 50 species. The genus exhibits distinctive ecological diversification and occurs in terrestrial, epiphytic, and lithophytic life forms. Moreover, Cymbidium section Pachirhizanthe lacks foliage leaves and has an obligate mycotrophic nutritional existence. In this study correlation between various morphological and anatomical characters and ecological characters was tested for most species of Cymbidium and its sister groups. Furthermore, a molecular phylogenetic tree of Cymbidium (Yukawa et al. 2002) was used to examine phylogenetic constraint of these characters. The following insights were provided: (1) In Cymbidium, lithophytic and terrestrial life forms were likely to be derived from epiphytic habitat at least three times. (2) The obligate mycotrophic lineage, Cymbidium section Pachyrhizanthe diverged from a terrestrial progenitor. (3) The seed of epiphytic species showed higher hydrophilicity and larger dimensions than that of terrestrial species. (4) The seed size of obligate mycotrophic species decreased greatly in comparison with its sister photosynthetic species. (5) Development of ramified rhizomes was found only in terrestrial species. We found that this type of the rhizome is the principal dwelling for mycorrhizal fungi. (6) In this genus, development of sclerenchymatous fibers in leaves is correlated to the degree of epiphytism. (7) Differentiation of palisade tissue and amphistomaty are likely adapted to high light stress because the species possessing these characters inhabit trees at exposed positions. (8) Orchid-type endomycorrhizal fungi and tree ectomycorrhizal fungi were found in Cymbidium roots and/or rhizomes. Although terrestrial Cymbidium species symbiose with both types of fungi, epiphytic species show symbiosis only with Orchid-type endomycorrhizal fungi. On the other hand, obligate mycotrophic species symbiose exclusively with tree ectomycorrhizal fungi.

Tomohisa Yukawa - Tsukuba Botanical Garden, National Science Museum, Tsukuba Japan,
Kazumitsu Miyoshi -Department of Biological Production, Akita Prefectural University; Akita Japan;
Jun Yokoyama - Department of Ecology & Evolutionary Biology, Graduate School of Life Sciences, Tohoku University, Sendai , Japan;
William L. Stern - Department of Botany, University of Florida, Gainesville - U. S. A.




Any kind of reproduction (print, digital or anyone other) of any type of material of this site - texts, layout, photos, images and others - is strictly forbidden without previous written permission by the authors.