My understanding has always been that no matter where the culutre came from,
within a couple of months, your local microflora will take over in your
starter. If that's true, then that would explain why your cultures change
their flavor characteristics.

Is this true? Or am I repeating a sourdough urban legend here?

Sure seems true. My starter has always had a very, very mild flavor unless I
work the Dickens out of it by keeping it stiff and doing two long, slow bulk
rises before the final proof. However, when I gave some to a friend of mine
who lives just 6 miles away (though it's not near the river, like me, but is
instead at a higher elevation near a wetland), within three months, she had
super tangy bread. And I know she's not doing anything differently from me.
I taught her how to make bread, myself.




--
Jeff Miller