Two species of bacteria share a single Petri dish. Both eat the same food, and by all rules, one should outcompete the other. But in reality, they often live together for years. The secret lies in knowing when to leave.
Bacteria don't stay put. When a stranger appears nearby, they start moving faster. Not immediately, though: first slowly, then, when the strangers become numerous, abruptly, as if an alarm goes off. Scientists call this 'fleeing from a neighbor' and tested it in a computer model.
It turns out that this behavior spontaneously creates order. Bacteria of one species gather in patches, and those of the other in different patches. The patches don't mix, and each species gets its own share of food. Even the weaker species, which would lose in a well-mixed environment, now survives. Sometimes it even becomes more abundant than the strong one.
So a simple rule—'speed up when a stranger is near'—explains why so many species live side by side in nature without destroying each other.
In the model, the weak species sometimes becomes more numerous than the strong one — simply because it flees faster and grabs empty spots.