Rodolfo Solano Gómez was born in 1968, in Mexico
City. He studied biology in the Universidad Nacional Autónoma
de Mexico and got his Ph.D. in the same institution.His main orchids
interests are the systematics of Pleurothallidinae subtribe and
the taxonomy and conservation of Mexican orchids. 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 studying the Oaxacan orchids. Since several years
ago his group of interest is the Pleurothallidinae and
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".
ON: The classification
of Pleurothallidinae subtribe (one of the biggest) is one of the most
complex and many scientists consecrated their time in studying it and
suggesting many changes. So all those studies concerning the phylogenetic
classification arose a great expectation. As this subtribe particularly
interests you and since you have been working with Alec M. Pridgeon
& Mark W. Chase in their reclassification of Pleurothallidinae,
could you give us some explanation about those changes?
RS: Since the 19th century, Pleurothallis
was the miscellaneous genus in Pleurothallidinae, in which was
placed all Pleurothallidinae that not belong to any other genus
of the subtribe. Several authors, including from John Lindley to Carl
Luer, recognized the heterogeneous nature and the convenience to segregate
Pleurothallis into several genera. Of course, to change the delimitation
of Pleurothallis affects the classification of all subtribe, since the
groups that not belong to Pleurothallis sensu stricto, should
be considered as different genera or merged into other ones. We have
a very interesting and confusing situation in Pleurothallidinae,
common in many others orchids group: the recognition of the genera was
based on the floral morphology, but it isn’t indicative of relationships
among them, but the floral adaptations with their pollinators. So, we
can’t consider two pleurothallid genera as close related only
based on their floral similitude, since the similar flowers are reflecting
the evolutionary route from which they have obtained the same pollination
syndrome. An example is in the very similar flowers of Stelis and
Platystele, but these genera aren’t close allies. On these
grounds, we used other information type, not floral, to obtain evidence
about the relationships among the Pleurothallidinae genera. We
employed three different sequences DNA, two from plastids and one from
nucleus. This way, we have three different molecular histories but also,
we can combine these into one combine history.
ON: Do you think that only DNA sequences is enough for classification?
I mean, do you think that only the phylogenetic classification is the
way for modern botany and the classification based on floral characters
should be completely abandoned or both ways should be studied together?
RS: I think that DNA sequences have some good
points over the floral morphology. Provide us with much more characters,
they haven’t affected by environmental factors as is the case
of the floral characters, and can be codified in a better way comparing
with the floral ones. Certainly, I’m forming into the phylogenetics,
so I think that this is the better way in which we can do a reclassification
of Pleurothallidinae. Now we have a system where the genera are
recognized as monophyletic groups (a genus is integrated by all species
with the same evolutionary history and the same ancestor throughout
the time) and the species that not belong to this group, should be placed
in other genus, its respective monophyletic group. On the other hand,
I think that we shouldn’t abandon the floral morphology in the
classification of the subtribe. We should analyze adequately the floral
variation in all subtribe to select and codify those characters useful
in the classification. But not only the floral characters should be
analyze, also the vegetative ones (habit, stems, sheaths, leaves, inflorescences
and else). In the last years I have been analyzing the morphological
variation from Pleurothallidinae to find characters useful for a key
of the genera. I found that some vegetative traits are more useful than
the floral ones for the first entries of the key. They can separate
groups of genera, such as the genera with annulus, the genera with lepanthiform
sheaths or the genera with sessile leaves. Then, the floral characters
can separate the genera within one of such groups, as the genera with
lepanthiform sheaths: Lepanthes, Lepanthopsis and Trichosalpinx.
On this basis I did the key of genera for Genera Orchidacearum volume
4. I wait use this information to find the morphological apomorphies
that define the genera of the subtribe (a trait which is derived and
shared among all members within a genus). These apomorphies are unknown
from several genera in the new classification and this is one of the
main critiques to it.
ON: The classification obtained by the use of data from 4 DNA sequences
can be considered definitive or should you wait for more changes?
RS: Reality there were three different sequences,
they were analyzed first independently and then combine into a single
analysis. I think that we can wait for some changes in the phylogenetic
classification of Pleurothallidinae. The subtribe is so great
and diverse and there weren’t included all genera and infrageneric
groups of it. For example, the sampling for Masdevallia, Pleurothallis,
Specklinia, Stelis and Trichosalpinx is incomplete. I wait
that a better sampling and a specific phylogenetic study for these genera
let us redefine their phylogenetic status. I suspect that Specklinia
and Trichosalpinx aren’t monophyletic groups and possibly
these should be segregated, but to do this are necessary additional
studies. My work with Stelis sensu lato provide evidences for
a infrageneric classification of this genus. Daniela Abele (from Venezuela
and actually in Germany) has studied the phylogeny of Masdevallia,
her results shows that the recent genus Diodonopsis is within
Masdevallia and possibly should be returned to it.
ON: As Alec Pridgeon and Mark W. Chase said in their article (2001,
in Lindleyana -A Phylogenetic Reclassification of Pleurothallidinae),
the circumscriptions of generic and infrageneric taxa in this subtribe
have plagued orchid taxonomists for the past two centuries. Do you consider
that it is still hard or the new propositions have already solved all
RS: In the last two centuries the classification
of Pleurothallidinae, based on morphology, was focused on the
delimitations of generic and infrageneric groups, which is more apparent
in the Luer’s taxonomic treatments. Today, we have evidences from
DNA sequences to evaluate the relationships among the subtribe members
and to reconstruct a new classification system. The main goal of this
study was establish the correct delimitation of each subtribe genus,
making each genus a monophyletic group. Sometimes the botanist aren’t
agrees with the delimitation of these groups, but as biologist, we have
to know some elementary phylogenetic principles to understand the reality
of such monophyletic genera. The phylegenetics isn’t a mode, but
the science that now and in the future provide us the tools to make
the biological classifications. Actually, from these studies we only
have the phylogenetic delimitation of all Pleurothallidinae genera.
There aren’t infrageneric classification in anyone genus yet,
this is the goal of the phylogenetic studies within the subtribe. Genera
as Acianthera, Lepanthes, Octomeria, Masdevallia, Pleurothallis,
Specklinia and Stelis are great and morphologically heterogeneous,
so that perhaps an infrageneric classification should be necessary for
them. Possibly the DNA sequences data can’t useful for this purpose,
since their divergence values are low and the resolution obtained within
each clade is poor. However, we have to find other data type, such those
from anatomy, morphology, palinology and else, in order to obtain more
resolution. The DNA sequences data are very good, but they aren’t
the only one, the better results are obtained when we can add other
ON: Orchidists have difficult to adopt a new nomenclature and in general
it takes time to adopted, it is normal. However you said, in your lecture,
that most authors still use the systematic classification.Why does it
happen? Why those studies raise so many resistance?
RS: During the past century the Pleurothallidinae
was a group poorly known by the orchidist, but at the end of this
century, it become one of the more known orchids groups. This fact was
possible due that Dr. Luer has been working with this group since the
mid 1970. Luer elaborated the more accepted classifications for the
subtribe and Pleurothallis and most orchidist followed him. On the other
hand, almost all orchid growers have been using the Luer’s classification
to name the Pleurothallidinae plants. So, at the start of the new century,
this classification was widely accepted, both by the botanist as the
growers. Is hard to accept changes as soon these arrive, the people
don’t like it easily, including the scientific community too.
Some traditional orchidists have two critiques to the phylogenetic studies
in Pleurothallidinae. One is the poor sampling for some genera,
the other one is the absent of morphological apomorphies which let us
recognize the genera. I think that these are the main facts for which
the phylogenetic classification isn’t widely accepted. Also, there
are necessary still the combinations for many species, which aren’t
provided by Pridgeon and Chase. We have the names for all Pleurothallidinae
that occur in Mexico, according to the phylogenetic system. When
the orchidsts have the names for all species Pleurothallidinae
from every Neotropic country, the phylogenetic system will be universal.
ON: In your lecture, you talked about a study that provides a more useful
classification system and the apomorphies for the recognition of genera.
What is this study and which are your most important conclusion?
RS: As I tell you
in other parts from this interview, the DNA sequences aren’t the
unique data source to evaluate the relationships within one group, there
are additional sources, such as morphological, anatomical, palinological,
chromosomal, chemical and else data. A natural classification should
be include all these data, but is difficult because some data are absent
today. On the other hand, I think that the genera should recognize by
the global morphological aspect of their plants, that’s main,
by visible traits. But to do it is require a character analysis that
provide us an useful morphological data set and then use it in the phylogeny
and classification. Actually I have a morphological data set for Stelis
sensu lato and combine it with ITS sequences data to evaluate their
phylogenetic relationships. From this study I find that Stelis
sensu lato is really a monophyletic genus, within it is embedded the
Stelis sensu stricto group, as a monophyletic group too. Here we
have two options, let Stelis with its traditional delimitation
and propose the relate groups as different genera. The other option
is consider all these groups as only one genus. Pridgeon, Chase and
I think that the better option is the second, since in the first we
have to create several new genera, which imply more taxonomic difficulties
within the Pleurothallidinae. The phylogeny of Stelis sensu lato
provide us evidence to consider necessary an infrageneric classification,
this genus can be divide into some subgenera. Also, this study provide
us the morphological characters from which we can recognized the genus
and their possible subgenera. However, there aren’t apomorphies
from these groups, since a combination of some morphological traits.
There is necessary include other data type to obtain more resolution
and support for these groups.
ON: You also mentioned species with a confused delimitation such as
Anathallis, Pleurothallis, Specklinia and Stelis. Which
are the differences between those specific genera?
RS: In my talk I mentioned that the delimitation
of some genera still is confusing, such as Anathallis, Pleurothallis,
and Specklinia, mainly, but Stelis is a well supported
genus in the molecular phylogeny. The sampling from these genera was
poor and the generic delimitations were made from the positions of the
species included. This is one of the main critiques to the phylogenetic
classification. Now we have to do a more inclusive sampling to evaluate
the phylogenetic status of some genera, mainly the more diverse. This
should be the next step, the phylogeny form each Pleurothallidinae genus.
My study with DNA sequences from Central American Pleurothallidinae
shows that some species not belong to the genus in which was assigned
for Pridgeon and Chase. For example, Anathallis platystylis and
Anathallis racemiflora (its correct specific epitheton is quadrifida)
weren’t included in the molecular phylogeny, but I have sequences
from both species and these are placed within Stelis. I think
that other Anathallis species really should be placed in Specklinia,
since these have more affinities with the second rather with the other
Anathallis, such as A. fuegii and A. yucatanensis.
The new delimitation of Pleurothallis is still preliminary, since
some groups that remain within it haven’t been sampling, as the
Brazilian Pleurobotryum and some monotypic groups (Pleurothallis
dresslerii). Probably these groups should be considered within a
genus different from Pleurothallis.
After solve these problems, probably Pleurothallis sensu stricto will
be a more or less homogeneous genus, including the Luer’s Pleurothallis
subgenus Pleurothallis and some groups such as Luer’s Ancipitia,
Rhyncopera and Scopula. However, there are difficulties to
distinguish an Anathallis from Specklinia or Stelis.
Anathallis is formed by two species groups, one of them include
A. acuminate and similar medium to large species to this. The other
group include small to minute species as A. barbulata. Specklinia
is more heterogeneous, but the most species shows the floral morphology
present in Specklinia grobyi, the plants are small to minute,
generally with abbreviate stems, annulus near the base stem raceme with
successive flowers. Stelis now seem be the miscellaneous genus in the
subtribe, different from its early conception, in which a species was
clearly recognized from other genera. Actually Stelis is distinguished
by a combination of some vegetative traits: stem more or less elongate,
annulus near the stem apex, leaves with a petiole and raceme with simultaneous
ON: Do you know the work developed by Fabio de Barros (Botanic Institute
of São Paulo) about Pleurothallidinae? In 1983, he published
Specklinia grobyi (Batem. ex Lindl.) F. Barros, (Hoehnea 10:110)
which is included in the work above mentioned.
RS: I have read some Fabio’s works, personally
I don’t know him. I know too that Fabio transferred Pleurothallis
grobyi to Specklinia, so that the Pridgeon and Chase’s
name for this species is illegitimate. Fabio recognized the affinities
of this species with Specklinia lanceola, the species type of
this genus, as well as the convenience to consider it as a different
genus from Pleurothallis. There are a great number of specific
names in the Pleurothallidinae, when Pridgeon and Chase transferred
many Pleurothallis to other genera, several combinations from
they became homonyms within some genera. I found many of these homonyms
in Stelis. On the other hand, Pridgeon and Chase forgot that
the basionym of some species has been publishing in other genus, not
Pleurothallis and when they did their combinations, they transferred
the Pleurothallis name, not the basionym. An example is Pleurothallis
setosa, the species basionym is Masdevallia fimbriata, so
that the correct name should be Specklinia fimbriata, not Specklinia
setosa. Fabio has other contribution to the new classification of
Pleurothallidinae, he recognized that Pabstiella is a validly
published name (early it was considered as illegitimate name). So, Anthereon
is an illegitimate name since it was based on the same type of Pabstiella.
ON: Do you like to add something?
RS: As I mentioned above, is difficult accept
the recent changes in taxonomy, there are require some years to do it.
However, the recent classification for Pleurothallidinae, as
well as the other orchid subtribes, have scientific basis and are constructed
on cladistic criteria. Actually the taxonomy for all flowering plants
is based on the same criteria and every day more botanists accept the
phylogenetic system of classification. My opinion is that in the future,
as orchidists we should accept this system and avoid use more than one
classification for orchids. But we should take care with increase the
genera number, we don’t should be splitter in extreme. I think
that the better way is when we have some groups very close relate forming
a very supported clade, we should recognize it as only one genus instead
of recognize each small group as a different genus. The latter way is
chaotic in the taxonomy.
photos and comments
was segregated into several genus, each one is now a
monophyletic group. One of the these genera is Acianthera,
which is very common through all American tropics. In
general terms, this genus is characterized by its leaf
sessile, stem without annulus, raceme shorter than the
leaf merging from the apex stem and sepals pubescent.
These traits can see in A. chrysantha and A.
majakoluckae (a Mexican close ally to A. pubescens).
But Acianthera include too species as A.
johsonii, in which the raceme arise from the base
stem and that in the past were considered (and recently
by Luer himself) in the genus Brenesia”.
genus segregated from Pleurothallis is Anathallis.
This is distributed in all American tropics too, but
is more common in South America. The genus is formed
by two groups, one of them grouped medium to large plants,
with the vegetative morphology and the raceme similar
to Stelis, but the flowers with sepals free,
long acuminate and internally pubescent, as it can see
in Anathallis dolichopus. The other group is
formed by minute plants, with obsolete stems, raceme
abbreviated, successively flowered and lateral sepals
frequently fussed into a synsepal, One member of this
group is A. minutalis”.
“Even though Pabstiella
was proposed as genus since 1970s, only recently it
was recognized as different from Pleurothallis.
This is a small genus, more common in South America,
Pabstiella trypterantha is a member of it.
Pridgeon and Chase proposed the name Anthereon
for this genus, since originally they ignore that Pabsteilla
was published as valid generic name”.
is a more understandable genus and this include the
pleurothallids with cordate leaves, as P. antonensis,
those species with similar flowers on a simultaneously
flowered raceme, or species as P. nelsonii,
which in the past was include in the subgenus Ancipitia.
However, some pleurothallids groups haven’t included
in the subtribe phylogeny, so that its phylogenetic
status is unknown. Temporally these groups are include
in Pleurothallis, until its correct phylogenetic
status will be solve. The Brazilian Pleurobotryum
(as the indeterminate species of the photo presented
here) is one of this groups”.
group segregated from Pleurothallis is Specklinia,
which include also the early genus Acostaea.
Although it is a morphologically heterogeneous group,
formed by minute to medium plants, there are a combination
of traits to distinguish their species: stems short
or abbreviates, annulus near the middle stem, leaves
with a petiole and successively flowered raceme. Florally
the genus is diverse, as can see from the three photos
presented here: Specklinia alata, S. endotrachys
and S. marginata (close ally to S. grobyi)”.
Stelis is the more heterogeneous group
in the subtribe. Originally the genus was easily
recognized by its very constant floral morphology,
as can see in Stelis chiapensis. A small
group of Stelis with entire stigma as
in S. rubens, not bilobed, was proposed
as different genus, Apatostelis, but
is part of Stelis sensu stricto. Other
small group, represented here by S. rufobrunnea,
were transferred to Pleurothallis subgenus
Pseudostelis, but this group is also
within Stelis. Actually, the more controversial
members of Stelis are those group that
early were part of Pleurothallis, as
subgenera Dracontia (represented by Stelis
pachyglossa), Effusia (represented
by Stelis quadrifida), Physosiphon
(represented by Stelis emarginata, before
named as S. tubata) and Unciferia
(represented by Stelis immersa)”.
Thank you very much
Photos by Rodolfo Solano
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