Personally I agree with maybe half of this map. Folk metal, melodic death metal, industrial metal, and nu-metal are all clearly related to heavy metal. But Are all these types of music truly derivatives of heavy metal, or psychedelic or hard rock which came first? One of the islands that I agree most with is the one just under heavy metal. The 90's music definitely lead to post grunge which developed into nu-metal which is mostly attributed to the 2000's. The bottom right island is only half right however. Deathcore and hardcore are definitely related to emo but in no way did emo come first. Also ska and punk rock are pretty close and possibly show a few similarities to emo but are so distant they really should be different islands. A few of the other islands that I agree with are country, folk, oldies, blues, and jazz being related to one another.
Most of the parts of the map that I disagree with are on the left side. For example, techno, electro, and trance have no business being anywhere close to "chill-out." And why aren't acustic, reggae, and psychedelic all close to "chill-out?" Additionally didn't indie pop develop from brit pop and not the other way around? Also I personally feel that ambient and post rock are so "far out" that they really should just be little islands in the middle of no where. Finally, one of the islands that bothers me the most is how in the world is psychedelic anywhere close to related to whatever doom metal is.
In conclusion I feel that this map is based on a really neat concept, it just needs to be revised.