In article ,
Stewart Robert Hinsley wrote:

It hybridises readily and naturally, doesn't it? Lack of natural
inter-fertility is the usual criterion. As you should know, the
classification of such things is very much a matter of taste,
because plants have truly weird sex lives.

That however is not definitive. The red (Silene dioica) and white
campions (Silene latifolia) hybridise readily and naturally, but still
seem to be could species.

Not in the same way. The key is the claim that the hybridisation
is causing the elimination of the separate populations - i.e. the
two 'species' aren't stable in juxtaposition. There are plenty of
good species that will hybridise, but where the parent populations
remain stable even in the presence of the other and the hybrids.

If the only way to keep them distinct is to keep them physically
separate, then it makes a mockery of the term species. Yes, I know
that botanic species is as much a Linnaean as a Darwinian concept.


Regards,
Nick Maclaren.