[lisper]

This is a common misconception. The collection is the unit of replication, but the gene is nonetheless the unit of selection. This argument was laid out in excruciating detail by Dawkins, but the TL;DR is that reproductive fitness can only ever be measured relative to some environment, and all the other genes in a replicative unit are (part of) the environment for a gene and its alleles.

[phkahler]

Collection, chromosome, Gene, base pair. Selection happens at all these levels.

[lisper]

Nope. Selection can only happen at the level of something that has an effect on the phenotype. That's the definition of a gene.