I'm sorry, but you clearly don't understand the issue. The concept that a species arises that subsists on an abundance of a certain food is not only consistent with evolution, it more or less confirms it.
It helps to remember that evolution is not an intelligent Deity but a concept revolving around survival and reproduction. If nuclear war wipes out most of the life on earth, and the only thing left around is cockroaches, a species that thrives on the abundance of cockroaches will emerge to the top of the food chain. If there's an abundance of herring, species that can't thrive on it won't benefit from it - species that do, will.
Pandas thrive on bamboo - it grows very fast and in the right environment, will spread everywhere. Wipe out bamboo or otherwise threaten their environment, and the delicate balance is destroyed. Koalas on the other hand, survive almost exclusively on eucalyptus leaves. Besides having a very low metabolic rate and therefore needing very little, there's extremely little competition for the food, thus allowing them to benefit from it.
I can't begin to understand why you think this would suggest "design". If anything, it totally corroborates what evolution teaches. I would have to suspect an intelligent designer wouldn't make these kinds of symbiosis so extremely delicate, and would make species have a "back-up" plan.
Humans have made use of this basic concept for millenia - kill what it eats, kill the species.