Yeast communities of the cactus Pilosocereus arrabidae as resources for larval and adult stages of Drosophila serido.

The feeding behavior of Drosophila serido on the yeast communities of necrotic stem tissue of Pilosocereus arrabidae were studied in a sand dune ecosystem of Rio de Janeiro, Brazil. The prevalence of cactophilic yeasts including Pichia barkeri, Candida sonorensis and Geotrichum sp. in the crops and external surfaces of D. serido reflected its association with the cactus habitat. The effective number of yeasts vectored on the surface of flies was higher than that in the crops. Also overlap between the yeasts from stems and from crops was partial suggesting selective feeding by the flies in the substrates visited. The females had a higher effective number of yeast species and a lower similarity than males with the yeast community of P. arrabidae. This was probably related to the search for oviposition sites by females. The presence of Pichia thermotolerans-like and Pichia amethionina var pachycereana in the flies, but not in P. arrabidae stems, indicated that D. serido was not limited to this cactus species. The larvae and adults lived in different patches with the adults feeding in patches with higher yeast species richness. The larvae had a narrower feeding niche and higher overlap with P. arrabidae, and preferred P. barkeri and Pichia cactophila as food. Adult flies fed on patches with the most frequent yeasts except for P. cactophila. Pichia caribaea was found in higher frequency in the adult crops than in the stems. Our data suggested that there was food selection and diet partitioning between adult and larval stages of D. serido.