DEVELOPMENTAL BIAS. “Cichlid fishes in Lake Malawi are more closely related to other cichlids in Lake Malawi than to those in Lake Tanganyika, but species in both lakes have strikingly similar body shapes. In each case, some fish have large fleshy lips, others protruding foreheads, and still others short, robust lower jaws.”
http://www.nature.com/news/does-evolutionary-theory-need-a-rethink-1.16080