Host use and developmental instability in the cactophilic sibling species Drosophila gouveai and D. antonietae

Abstract

The Drosophila repleta group encompasses an ensemble of species that inhabit desertic areas unfriendly to other drosophilids. These species have a tractable ecology since they breed and feed on necrotic tissues of Cactaceae making them suitable models to investigate the role of host plant shifts in diversification. Most species have their own primary host plant that may be shared with a closely related species. However, the consequences of host plant shifts from primary to secondary hosts have not been thoroughfully studied so far. We investigate the effect of the rearing cactus host on developmental instability and performance in D. gouveai and D. antonietae a pair of closely related cactophilic sibling species and their F1 interespecific hybrids reared in primary and secondary host cacti. Fluctuating asymmetry for wing size was significantly greater in flies of both species reared in their respective secondary cactus host as compared to those grown in the primary host. Interspecific hybrids also exhibited host dependent levels of FA. However, hybrids did not show increased levels of FA as did pure parental species, suggesting that hybridization per se did not affect developmental stability. Finally, even though cactus host shifts affected different measures of fitness (larval viability and adult size), we did not detect a consistent relationship between FA and fitness in all isofemale lines of both species. Our results suggest that FA cannot be used as a sensitive indicator to reflect genetic and phenotypic quality in all cases and its application is discussed.