[Elsie]

By specializing to exclusivity on a particular food source (bamboo) which has subsequently become constricted in it's range.

Is this like that cactus in the desert that is the ONLY food for a certain bird (or insect; I don't remember the details) and that creature is the ONLY pollinater of it?

[From many - one.]

Yucca and yucca moth.

[Stultis]

Is this [Pandas and bamboo] like that cactus in the desert that is the ONLY food for a certain bird (or insect; I don't remember the details) and that creature is the ONLY pollinater of it?

Sure. Evolution can't "know" (and doesn't "care") that it may be staking important matters on an ultimately impermanent resource. How could it? It only "knows" that the resource is available here and now. All evolution can ever act on is the present (or then present) creature and environment as they present themselves.