Based on my own personal, anecdotal, and subjective observations, a sourdough start has a home. I mean, it seems to belong near where it was first started. It's as if the wild yeasts know from whence they came and prefer to be in that place.
For example, I have a sourdough start that came down from my Aunt Alice, my grandfather's aunt. She made this start in the 1930s, and it has proliferated throughout the family. I got the start from my grandmother, and Cousin Edith had some of the start, and Cousin Lillian did too, and so did various other relatives who lived nearby.
Aunt Alice lived about ten miles from where I grew up and not more than forty miles from my grandmother. My grandmother made the most incredible sourdough English muffins - just the right amount of rise to the dough, perfect air pockets, that tangy bite from the sourdough itself. With her homemade raspberry jam, ye gods I don't think there has ever been a better combination in this world.
Anyway, I got the start from my grandmother and starting baking bread and English muffins and it went really well. Then when my wife started graduate school, we ended up moving about 300 miles away from home. There was also a drop in altitude from about 4000 feet above sea level to about 700. And my sourdough went flat.
Oh, it didn't quit working or anything that drastic. It just was slower to rise, never rose quite as high, and it lost some of its bite. However, anytime I'd go back home and take my start along, it would perform like my grandmother's again. It's as if it knew it was home and celebrated by rising a bit higher, a bit faster, letting out just a touch more of the sourdough flavor.
Now that I'm back near where I grew up, the sourdough is back to normal. But when my cousin came up to visit and took some home with her to Texas, about 1500 miles away, she never had good results at all.
Maybe it's all in my head. Maybe sourdough acts exactly the same no matter where it is. But I don't think so. I really believe that sourdough works better, tastes better, and truly is better when it is near its ancestral home. San Francisco sourdough is best in San Francisco. Alaskan sourdough is best in Alaska. And Aunt Alice's sourdough belongs here.