Adaptations of Drosophila and yeasts: their interactions with the volatile 2-propanol in the cactus-microorganism-Drosophila model system.

The interactions of yeasts growing in decaying cactus tissue with and without 2-propanol were studied with respect to the costs and benefits provided to three cactophilic Drosophila species (D. mojavensis, D. arizonensis and D. buzzatii). Two common cactus yeasts, Candida sonorensis and Cryptococcus cereanus, which can tolerate and metabolize 2-propanol, provide benefits to the three Drosophila species in the presence of the alcohol, as compared with another common cactus yeast, Pichia cactophila, which has less tolerance and cannot metabolize 2-propanol. Because 2-propanol is commonly found in decaying cactus tissue and C. sonorensis and Cr. cereanus are also frequently recovered from the rotting tissue being utilized by the Drosophila species, the interactions described here are viewed as a possible adaptation in which the yeast provides benefits to one of its vectors by metabolism of 2-propanol in the habitat.