Speciation & Classification
I believe Maureen's statement "it seems to me that other factors
outweigh cross-fertility in botanical classifications. But then again,
plants seem to get reclassified rather frequently which suggests that
the rules are constantly changing." is misleading. Classification is
designed to reflect our best knowledge of evolutionary relationships,
not convenience for identification. The central core of species
separation is the degree of fertility. This can be the result of
barriers which are physiological, behavioural or geographic but lower
fertility is assumed to be the best indicator of greater evolutionary
separation and this should be reflected in the classification. Although
there is a constant ground swell of systematic revision, it is always
designed to get us closer to the evolutionary relationships and is more
often at the generic or higher levels.
Ian, in Ottawa where the snow has cleared over three irises, proof that
there is life after winter.