Modifying Hawaiian Drosophila laboratory diet with material from the wild: Phenotypic response to microbial and nutritional variation

Abstract

Invertebrate conservation and research are necessary to protect a large portion of Hawai`i’s nativefauna. Because fourteen species of Hawaiian Drosophila (Hawaiian picture-wing flies) are listed as endangered, with many more species in decline, understanding the biology and ecology of these animals is critical to their conservation. Research indicates that Hawaiian Drosophila exhibit phenotypic changes in reproduction and longevity based on their microbiome community assemblage. Lab-reared organisms maintain different microbiome community compositions than their wild counterparts, and Drosophila microbiomes are predominantly formed from diet. Therefore, understanding the phenotypic response of lab-reared flies to a wild-derived diet is necessary to establish robust populations of lab-reared Hawaiian Drosophila in their historical habitat range. Here, we supplement lab-reared Drosophila crucigera diet with rotting host plant to gauge the phenotypic effects of “wild” sources of nutrition. Flies exposed to a wild-derived diet did not exhibit increased fecundity compared to flies fed on a standard lab diet. However, flies who were exposed to frass from flies given a wild diet had higher fecundity than flies exposed to frass derived from a standard diet. Internal fly microbiome sequencing revealed that fungal diversity was impacted when flies were directly exposed to host plant substrate. Bacterial diversity was affected by inoculum that consisted of frass or a suspended solution of host plant microbes. Achieving effective diet supplementation for Hawaiian picture-wing flies in lab culture may ultimately improve rearing methods and conservation efforts to reintroduce endangered species to the wild.