What are you on about, Dave? Natural selection applies everywhere. Young, old, alive or dead. Why do you think we have a duopoly of just two mobile OSes? Natural selection!

Even if the dominant species on some distant planet were replaced with AI, the natural selection would not stop. Small fluctuations or even blind chance (like the one that did away with Mr T-Rex to clear the way for you) would result in some of them moving up while others dying away.

Energy? Ultimately, natural selection is driven by the struggle for resources. That's what it is all about: resources are limited, which means not all indoviduals can survive and reproduce. Most of them must die. Which ones die and which ones survive and produce the next generation, that is where natural selection steps in.

Resources can come in many forms. Materials, energy, even information.