Re: Iris setosa (response)

 One of the things
>that bothers me about the occurence of I hookeri (= setosa var
>canadensis) on the east coast of N America is how did it get there
>from the west coast? Did it originally occur on the entire north
>coast of an earlier N American continent and spread down the east
>coast to Maine and the Canadian maritime Provinces? I would really
>like to know. Anybody have enough geology to offer clues?

The standard idea is that I. setosa was widespread in both NE Asia and
across North America at various times during the glacial period.  Glacial
advance would have separated western and eastern populations, which then
evolved enough differences to become separate species (Note that an animal
taxonomist would not consider setosa and hookeri separate species if they
could freely interbreed, but plant taxonomists use different criteria).  If
the separation occurred during the last glacial maximum, then hookeri as a
species may only be a few tens of thousands of years old.

Where is I. tridentata in all this?  Supposedly it cannot be crossed with
setosa or hookeri, but is included in the same series or subseries.  I have
plants of this species in my garden but they are poor "doers" and have
never bloomed.  It is found in N. Car., S. CAr., Ga. and Fla., separated by
a definite gap from hookeri.  Did the Japanese botanists who studied the
problem of hookeri include tridentata in their work?

Bill Shear
Department of Biology
Hampden-Sydney College
Hampden-Sydney VA 23943
(804)223-6172
FAX (804)223-6374
email<bills@hsc.edu>
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