What does this conch they found come to symbolize

It symbolizes a few things. The conch becomes a symbol of democracy. It is used to give even the lowliest of littluns a chance to speak. The conch also gives Ralph a certain amount of authority. He resembles an adult with a "megaphone" to the others. The conch comes to symbolize responsible authority from the old world. As visions of the old world quickly fade into nothing, so does the symbolism of the conch.