Host use and host shifts in Drosophila.

Over a thousand Drosophila species have radiated onto a wide range of feeding and breeding sites. These radiations involve adaptations for locating, accepting, and growing in hosts with highly differing characteristics. In a number of species, owing to the availability of sequenced genomes, particular steps in host specialization and genes that control them, are being identified. Many cases of specialization involve the ability to detoxify some component of the host. Examples include Drosophila sechellia and the octanoic acid in Morinda citrifolia, alpha-amanitin in mycophagous drosophilids, and the alkaloids in cactophilic species. Owing to the known ecologies of many species for which genomes exist, the Drosophila model system provides an unprecedented opportunity to simultaneously examine the genes underlying HOST LOCATION, HOST ACCEPTANCE and HOST USE, the types of selection acting upon them and any coevolutionary interactions among the genes underlying these steps.