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Taxonomy clarification

Medit-folks:

A while back (June 27), Rand Lee asked a question about plant taxonomy. I 
replied, but have since found out that the outbound email here was down 
that day. I don't recall seeing the message come back via Medit-plants 
or seeing any other (public) replies, so here it is, albeit rather late. 
Sorry if you all did see this before and it just didn't come to me!

Rand: here are some comments on your mail...

> Am I right in assuming that the term cultivar (abbreviation cv.) is used
> properly to refer to a plant arising in cultivation or maintained solely
> in cultivation?

Sounds OK to me.

>And that the term subspecies refers to a genetically transmissible 
>variation within a species, 

>That the term variety refers technically to any variation
> within a species or subspecies?

>where the term form or forma refers to a variation
> arising within a member of a species that may not be transmissible via
> seed but is reproducable via cloning?

There's a hierarchy of ranks here: species, subspecies, variety, 
subvariety, forma, subforma. That's laid out in the International Code of
Botanical Nomenclature, but there are no hard and fast rules as to which
rank a particular plant entity should belong.

I tend to regard subspecies as having discrete or semi-discrete 
geographical distributions and an often clinal variation, merging into each
other somewhat, and involving several characters. Varieties tend to be
distinct in one or only a few rather clear-cut characters and may share the
same distribution area. Forms I would define as very minor variations,
e.g., different colored flower variants.

>That the term type technically refers to
> a plant that is considered representative of a species or subspecies?

Not quite; a type is defined by the Code as follows:

"The application of names of taxa at the rank of family or below is 
determined by means of nomenclatural types ... A nomenclatural type is that
element to which the name of a taxon is permanently attached, whether it is
as a correct name or a synonym. The nomenclatural type is not necessarily
the most typical representative element of a taxon."

A type is a preserved plant specimen (dried and pressed, or in spirit) or
an illustration. It is a visual element that acts as a standard reference
item so that anyone may discern (or attempt to discern) what taxon (family,
genus, species, etc.) is meant by a particular name. As the code says, a
type is not necessarily a typical example of a taxon as generally
understood. In fact, a type specimen can be a specimen of a species other
than the species to which the name is question is normally applied. That's
when the trouble begins...

Nick.

Nick Turland
Flora of China Project, Missouri Botanical Garden, 
P.O. Box 299, St. Louis, MO 63166-0299, U.S.A.
Email: nturland@lehmann.mobot.org
Tel.: (314) 577-0269 (direct line, voice mail)
Fax: (314) 577-9438 (Flora of China fax)
MBG Web Site: http://www.mobot.org
Flora of China Web: http://flora.harvard.edu/china/
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