Jim, Thank you! I encountered the word Rassenkreis many years ago, used to describe exactly the situation David mentions. The example given was a moth, I think, with one end of the arc in Florida in the US, and the other end somewhere around Belize. But I somehow got a bad spelling of Rassenkreis in my head, and despite only being a couple of letters off was never able to get a hit on it - until now. A long-standing irritation resolved, just in time for Christmas! Steve On Fri, 21 Dec 2007, J.E. Shields wrote: > David, > > One expression for this that I recall is Rassenkreis, a breeding or racial > circle or arc. I think I have seen "cline" applied to the sort of > variational gradient you describe. We still someone who knows for sure to > enlighten us! > > Jim Shields > > At 07:04 PM 12/20/2007 -0800, David wrote: > >There is a botanical word I'm looking for it's something like gradient, > >but I don't think that's the word. It is used when referring to a species > >with a broad distribution which has one form at one end of its > >distribution and a very different form at the other end. The two extreme -- Steve Marak -- samarak@gizmoworks.com