In message , Nick Maclaren
writes

In article ,
Dave Poole writes:
|
| Moderation is the key - shift something that is clearly wrong, but
| don't go smashing things up and re-inventing new genera for no
| genuinely good reason. Especially when (as in the case of orchids ie.
| Odontoglossum, now decimated into half a dozen or more weird genera)
| they are clearly genetically compatible and therefore very closely
| allied.

I think that's a very good criterion. When inter-generic hybrids
are easy to produce, and fertile, that surely is evidence that the
generic boundaries are too specific?

You might like to consider the implications of that for Orchidaceae. For
example the hybrid genus ×Adamara is Brassavola x Cattleya x Epidendrum
x Laelia, so it would seem that at least two pairs of those genera
produce fertile hybrids.


| Crikey, I bet the Op (DC) is wondering what can of worms he's opened
| up. We haven't had a decent thrash-out like this here on urg for a
| long time. All because of an un-named Doritaenopsis hybrid too!

Well, we could get started on my bugbear - cladists! Obviously
Prunus spinosa needs to be abolished as a category, because it is
no sort of a clade (being a descendant of P. cerasifera and
Microcerasus/Prunus microcarpa and an ancestor of P. domestica).


Point of order. Prunus spinosa being an allopolyploid doesn't exclude it
from being a clade. Some allopolyploid species are - e.g. Spartina
anglica - and others - e.g. Tragopogon micellus - aren't.

Anyway, most cladists accept that species can be paraphyletic.

Regards,
Nick Maclaren.

--
Stewart Robert Hinsley