How different is one starter from another?
I've read a couple of recent comments by Mac, and sphealey, and others about the origin and character of sourdough starters. I'm still wondering what's the real scoop. I've read from highly authoritative, credible sources several different versions of various arguments about sourdough culture organisms and their origin and survivability in a culture.
I'll try to summarize the gist of them briefly:
1) There are only a handful of organisms in the world that will live in any sourdough starter. Therefore, there is not that much variation from culture to culture once they stabilize.
1a) It's more how you maintain the starter that determines which organisms are favored and active, and therefore what the flavor will be.
2) A geographic region's environment results in only certain characteristic organisms living in the sourdough starters in that region, so the flavor varies by region. You really can't maintain the character of a starter originated from a different region because it will inevitably be taken over by the organisms of that particular region.
3) You can maintain a sourdough starter's initial organisms if you are careful not to contaminate the starter. The character of the starter will continue indefinitely if you do that.
4) The yeast and lactobacillus bacteria come from the air into your culture.
5) The yeast and lactobacillus bacteria come from the skin and microenvironment of the kitchen into your culture.
6) Yeast and lactobacillus bacteria only come from the flours that go into the culture.
7) Yeast and lactobacillus bacteria can be contributed from raisins, grapes, yogurt, and other additives to a culture.
8) No, the organisms on grapes, raisins, yogurt aren't really the right ones and would do nothing or perhaps even contaminate and delay the development of a healthy culture.
9) Other? I've probably left some key argument out of the list above.
I'm wondering if any members of this site can put a finer point on this. Which of the many sources which make widely differing and often contradictory arguments should be considered most credible and why? What about personal experience or experiments you've done? Do you have any real examples where two cultures supposedly of different origin are maintained in the exact same way and yet taste very different? I'm looking for credible scientific evidence or definitive experiments people have done themselves and can attest to, if possible.