SPEC-setosa/hookeri

The idea that hookeri came from setosa or vis-versa is a somewhat
simplistic view of the probable origin of the two species.  It seems
most likely that there was one species that was spread around the
northern parts of North America.  When the ice age came, the ice
penetrated sufficiently far south in Central Canada that it killed off
this species in the middle and the two populations on either side simple
grew to be different.  Although it would be difficult to prove, the
setosa is probably as different, today, from the parent species as
hookeri.  We must also consider tridentata in the area of Florida,
Tennessee and the Carolinas, which is closely related to the other two
species and is now separated by much of the east coast area. This
species seems to have evolved into a semi-tropical cousin of the two
Arctic or semi-Arctic species. 

Ian, in Ottawa where it is quite mild - around 0C
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