Phenotypic response to a wild-derived diet in captive Drosophila crucigera, a Hawaiian picture-wing fly

Invertebrate conservation and research are necessary to protect a large portion of Hawai`i’s native fauna. 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 or microbes derived from a wild 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, both as an active microbe supplement and as inert plant/microbe material. Flies exposed to a wild-derived diet had increased fecundity and longer lifespan compared to flies that were not exposed to wild-derived host plant material. We also supplement lab-reared fly diet with fecal transplants whose donors were exposed to a wild-derived diet to assess the efficacy of host flies and their frass as a vector for transmitting microbiome-related benefits. Supplementing the diet of Hawaiian picture-wing flies with habitat-derived microbes to enhance reproduction and longevity in the lab may ultimately improve rearing methods and conservation efforts to reintroduce endangered species to the wild.