The mbuna cichlids of lake malawi are a model for adaptive radiation. currently, there are over 400 species, all derived from one common ancestral species. the graph shows the current count of species scientists have discovered in the lake. this diversification most likely took place because a) water temperatures varied with location. b) mutation happened at a very high rate in the lake ecosystem. c) different fish lineages evolved to take advantage of different foods. d) different fish groups were isolated by barriers within the lake from other groups.