What’s in a Name?!

[ralphrmartin]

... any name validly published is perfectly fine. Which is right, of course.

Not really, if you are a scientist. While there is no universal definition of a genus, it is quite clear from DNA work that some plants thought to be closely related are in fact far apart, and just look the same because of convergent evolution. So, if you believe that a shared genus name indicates a close relationship (rather than simply a similar appearance), which is really a given if you are being logical about things, some names are not "perfectly fine". In this vein, I guess many people would be upset if I called their Echeverias "cabbages" just because they look similar...

A good example alreadt given by Karl is Rebutia -plants that were thought to be all in this genus are now known to be divided into "true Rebutia" i.e. related to the plant which defines the genus, Rebutia minuscula, and "the others" Aylostera and Medilobivias, which now belong in the genus Aylostera.

So, while the names Rebutia muscula and Rebutia pygmaea are validly published, if you are being logical about things, you really ought not call them Rebutias, but Aylosteras.

[ralphrmartin]

As for Rebutia pygmaea, all being one species it is quite clear that this is a case of botanists lumping by size and form, which is pretty inexcusable in my view. I'm quite convinced that if these plants were all 20 cm tall, not 2cm, much more would be made of their differences, as they would be more noticeable.

I have myself seen 3 different "forms of R. pygmaea" all growing together in habitat in a very small area (less than 50 m x 50 m), with no evidence of interbreeding whatsoever. For example, the one with red flowers always coincided with short spines and close ribs, while the one with yellow flowers had whiter, longer spines, and so on. If these were all one species, it is very probable that we would have seen some intermediates (unless the genes for spine colour, flower colour, ribs, etc are all very close on one chromosome, which is rather implausible).

Anyway, at the end of the day, we must remember that "species" concept is just a human invention, and sometimes it is in good agreement with how nature works, and sometimes it is not - there are just populations which might or might not breed with each other, more or less frequently. This is particularly true for mountain cacti each on their own hill like "R. pygmaea."

[KarlR]

Okay, Ralph, maybe not «perfectly fine»
A poor choice of words. Using a validly published name from the 1800s which has been out of use for 200 years would be a bad idea, although it would still be a valid name.

Reicheocactus has largely been out of use for at least 50 years in most books I've seen (perhaps mostly because the name wasn't widely accepted to begin with), but it has now been resurrected by Lodé (although he uses the wrong species name for famatimensis in his book). Perhaps Homalocephala will be resurrected at some point, or perhaps Encephalocarpus will make a comeback.

What I meant with the «perfectly fine» comment was more related to names like Thelocephala, Brasilicactus or Chamaecereus. If you've always used these names I don't think it's so bad to continue using them even though they might not be the best possible choices considering current taxonomic views of the genera.

I do agree that genetics may well give us definite answers in the future, at least for genera. Hopefully it will be possible to distinguish on a species level too at some point, although what constitutes a species will vary depending on genus, I suspect.

I also agree with your take on Rebutia pygmaea (knowingly using the wrong name here ). It's the same with a lot of Sulcorebutias and Turbinicarpus.

[SpikyMike]

Thanks Karl and Ralph. Fascinating!

we must remember that "species" concept is just a human invention, and sometimes it is in good agreement with how nature works, and sometimes it is not

. Great quote