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.
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.
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.
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.
(Orchidaceae): Molecular Phylogenetics and Floral Morphology
By Alexander Kocyan (1), Ed F. de Vogel (2), Elena Conti (3), Barbara
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.
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
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.
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".
of life forms and mycorrhizal relationships in Cymbidium: insights
from molecular and anatomical data
By Tomohisa Yukawa, Kazumitsu Miyoshi, Jun Yokoyama, and William L.
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,
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.
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