From my limited experience in sourdough starters (mostly use mine for pancakes) your local strain of yeast may or may not give you the desired performance. That is why San Francisco is known for their bread, they have a great local yeast strain perfect for breads. Other places have yeasts better for brewing fermented beverages.
Sausage making is the same way (dry-aged, cured uncooked products) certain countries have a product which cannot be reproduced any other place in the world due to their unique local yeast & mold strains.
You may be able to get a specific bacterial strain to inoculate your sponge with, but it will not stay dominant for long until local strains take over.
Different wild yeast strains have different qualities to them, Some rise great, some brown great, while others do not do either and just smell good.
I believe it has to do with your geographic location and what strain of wild yeast has taken hold in your culture.
Even if you took a strain of wild yeast from one section of the world that performed perfectly, a short month or two after relocating it, your local yeast strain will win out and you will lose the qualities that you desired.
Can someone please confirm my statement?