Should a colleague receive authorship for identifying a research gap and reviewing a manuscript?
Identifying a research gap and reviewing a manuscript does not seem to warrant authorship to me.

Things would be different if your colleague had also worked with you in designing the study, experiment or research project to address the gap she or he identified. Or if your colleague had written part of the manuscript, say the summary of the existing state of the art.

Different disciplines have wildly different conventions on what constitutes enough contribution to warrant authorship. For instance, the American Psychological Association offers resources and a helpful scorecard. At the first link, we find:


  An author is considered anyone involved with initial research design, data collection and analysis, manuscript drafting, and final approval. However, the following do not necessarily qualify for authorship: providing funding or resources, mentorship, or contributing research but not helping with the publication itself.


This does not seem to cover your colleague's contribution under the specific conventions in psychology.

I suggest you look over the websites of associations in your field, and/or of relevant journals/conferences, perhaps the venue where you are considering submitting your work. There may be similar resources specific to your field.