Rebutia pygmaea

[Les.Needham]

In the New Cactus Lexicon, Rebutia pygmaea has 32 synonyms, 13 which are ascribed to Rausch and 16 to Ritter. This can mean that either (A) Rausch and Ritter were out to find as many new Rebutias as they could or (B) Hunt is hell-bent on simplifying the classification to such an extent that his species are becoming amorphous or (C) Rebutia Pygmeae is extremely variable. There is obviously no doubt that the species is variable. So where does that leave us? If we want to describe a particular variation, what convention may we use? Is it not best described by its synonym?
Come back Linneus. We need you.

[Phil_SK]

My convention is to write things like Rebutia pygmaea 'diersiana' and so on (although I need to get into the habit of calling them Aylostera pygmaea).

I think I'm right in saying that A. pygmaea is thought to have different plants lumped in together wrongly - that there are two different lineages that show convergent evolution. I don't know where this is written or which are thought to be which but I've heard it somewhere.

[Les.Needham]

Aylosteria! Where did that come from? Was Backeberg right after all?

[Phil_SK]

Ritz et al. published a phylogenetic tree a few years ago that showed that the Aylostera and Mediolobivia types were not very closely related to the Rebutia s.s., Sulcorebutia and Weingartia types, forming two groups in their tree. See the article here, especially Fig. 1.

It would be Spegazzini who was right, not Backeberg, though

[DaveW]

If plants occur in distinct different populations, dividing them into species is easier. However many plants are part of a cline, a continuous chain of plants gradually changing in the character of the plants as one goes from one end of their often very extended range to the other. Therefore the plants at one end look radically different to those at the other, with no significant breaks in the chain.

The problem for the classifier then is do you treat them as one obviously very variable species, or arbitrarily chop the chain into discrete chunks and call these individual species? The matter is further complicated by botanical priority. Ideally you would like to select a plant with intermediate characteristics to represent the cline, but plants were stumbled on by accident in the past and named (still are as collectors have seldom botanised all the likely habitats). That means the first plant named of this cline could have come from one of the extreme ends of its range, so shows characters very different from plants at the other extreme. Later collectors may also have stumbled across the cline in other places, or nearer it's centre, and named these as new too.

As said, what would be logical and botanists would like to do in that situation is to use the name that shows intermediate characters of their chosen species, but are precluded from doing so as the first valid published name for anything they include in the species take priority, even if a most untypical outlier.

Speciation (or classification) is simply a matter of opinion, not holy writ. So you are quite at liberty to use any valid name for your plants you want, be you a "lumper" or "splitter". You can bet your life this years definitive classification will be "old hat" in a few years time and a new one have replaced it.

The Rebutia example is a good one. For generations we have associated Aylostera and Mediolobivia with Rebutia. Now DNA Sequencing has proved that wrong in that they both spring from different lines of evolution, so only evolved to look similar since they inhabit similar environments. You can expect DNA studies to throw up more of these long held mistakes that were based solely on plant morphology in the past. Not only at generic level, but regarding which species are related to which and so can be reduced to synonymy under another older published one.

Yes, there was a certain commerciality to Ritter's names since the seeds were being sold commercially by his sister Frau Winter in the 1960's, and new names always sell better. I believe Backeberg's collecting trips were also commercially orientated. That is not to say that they did not find many sound species, but that was the age of the "splitter". Things have swung too far towards "lumping" now, but as with many things excessive swings towards "splitting" in the past are met by the excessive over correction towards "lumping" today. That will inevitably again lead to some dismantling of presently lumped genera and species into a less radical "middle of the road" classification, hence the need for the proposed rewrite of the first volume of the NCL when it appears, and that may be challenged by alternative classifications in future.

Somebody said elsewhere on the Forum, they hated it when people told them "you must call a plant so and so now". No you don't, as long as the name was validly published you can call it a Trichocereus or Lobivia not an Echinopsis, or a Notocactus not a Parodia if you so wish and the "Label Police" have no powers to arrest you. Mind you I am not sure their "dirty tricks department" are not behind the quickly fading so called "permanent label ink" for plastic labels so all trace of previous classifications dissapears after a few years and you need to rewrite with the new names they dictate.

DaveW

[ralphrmartin]

oops. Duplicate post.

[ralphrmartin]

In the New Cactus Lexicon, Rebutia pygmaea has 32 synonyms... This can mean that either (A) Rausch and Ritter were out to find as many new Rebutias as they could or (B) Hunt is hell-bent on simplifying the classification to such an extent that his species are becoming amorphous or (C) Rebutia Pygmeae is extremely variable.

I'm afraid lumping all these as one species goes in stark disagreement with the facts and definition of a species. I've been on one hillside in Bolivia where 3 "forms of Rebutia pygmaea"
- all in flower at the same time, within a few yards of each other
- with three different flower colours
- each flower colour having a distinct and different body type
- there were no intermediates

It's quite clear they were not interbreeding.

Now, if they had been 2 metres tall, no one would have hesitated for a minute to call them separate species. But becuase they are just 2cm tall, the differences get dismissed as minor.

So, these certainly should be given different names.

However, the real problem with many Aylosteras is that
- most species only grow on the mountains, or at least not in the valley bottoms
- deep valleys separate the mountains
- the population(s) on each mountain rarely if ever breed with those on the next mountain
- so the populations are going their own evolutionary ways, in some cases becoming new species, in other cases still being very much like those on another mountain.

Frankly, "species" is a human construct to simplify the description of nature, which works well in a lot of cases, but falls apart in others - this being one of them.

[Les.Needham]

I can well see the taxonomist's point of view, wishing to nail down the evolutionary tree. Perhaps the taxonomist should remember the collector's viewpoint (were taxonomists once collectors?). The collector wants to be able to describe a species, not a clump of species that possibly happen to have the same ancestors. We are not collecting DNA samples, we are collecting plants that we can see, and see to be different. And then we are told that they are the same species. So we must use three names, or even four, to describe the plant we have, in order to fit in with some system. Classifications were designed for plants, not plants for classifications.

[DaveW]

Humans come in many forms and colours but are still classed as a single species homo sapiens as they can interbreed.

I don't think everybody will ever agree on what a species is:-

http://deekayen.net/what-constitutes-species

http://www.biologie.uni-hamburg.de/b-online/e37/37e.htm

http://evolution.berkeley.edu/evosite/e ... cies.shtml

http://academic.evergreen.edu/curricula ... enotes.pdf

As to species on mountains separated from each other by valleys not being able to breed with those on other mountains, that depends really on the pollinator. If the pollinator, or even originally a bird consuming the fruit and hence eventually distributing the seeds can fly from hill top to hill top, even though the plants are separated by a valley they can be considered the same species. That can even apply if you have several non interbreeding similar species on one hillside and several similar non interbreeding forms on another, as long as compatible can be pollinated with compatible by their pollinators they can be considered the same species, even if valleys or unsuitable country intervenes between populations.

The old saying used to be "a species is what a competent botanist calls a species", a sort of rebuke to amateurs to keep their nose out of the professionals business of taxonomy, since it is beyond you mere mortals! However, unlike many other genera, the study of cacti would not have advanced very far without the dedicated amateur collecting in the field and having probably more knowledge of the variation of a population than some chair bound botanist in the past, simply receiving collected plants in the mail and then naming them.

The problem in future will be does one classify plants on their morphology, as in the past. Sometimes including species from different lines of evolution due to their similarity of appearance? Or by using modern methods like DNA Sequencing when it can be proved two plants evolved from different evolutionary lines, or are not closely related so should be different species, but which in the field and cultivation look virtually identical?

I remember the Society President,John Pilbeam raised that point in his Echinocereus lecture at the AGM Visually identical looking plants now being named as separate species, solely due to their internal chemistry.

http://www.herbarium.usask.ca/research/ ... t_1994.pdf

DaveW

[Les.Needham]

Phil_SK: I checked out the article you linked to. Very interesting. The final paragraph was encouraging:
"The results of our molecular phylogenetic analyses do not support either rigorous
and schematic lumping of genera, as was done in recent
classifications of Cactaceae, or extensive splitting. Our study
reveals that Rebutia species with hairy pericarpels are rather
distantly related to Rebutia species with naked pericarpels, so
in this case, a narrow generic concept as proposed by
Backeberg (1977) better approximates a natural system. In
contrast, Sulcorebutia and Weingartia should be united into
one genus, because neither molecular nor morphological data
reveal a distinction between these genera."
(I said Backeberg was right)