Abstract
Spotted-wing drosophila (SWD), Drosophila suzukii, has become one of the most widely studied insect species over the last decade, largely due to its recent invasion and rapid expansion across the Americas and Europe. Unlike other drosophilid species, which colonize rotting fruit, SWD females possess a serrated ovipositor that allows them to lay eggs in intact ripening fruit, causing significant economic problems for fruit/berry producers worldwide. Though an impressive amount of research has been conducted on SWD's ecology and physiology, aspects of their nutritional ecology remain ambiguous. This review synthesizes the research to date to provide a more comprehensive view of SWD's nutritional relationship with its fruit hosts and associated microbes. Overall, data suggest that SWD's ability to utilize novel resources is likely due to changes in their ecological, rather than physiological, niche that are largely mediated by microbial associations. Studies show that SWD's nutrient intake is comparable to other drosophilid species, indicating limited adaptation to feeding on lower-protein resources. Instead, data show that fruit protein content is a reliable predictor of host suitability and that fruit-microbe dynamics have a strong impact on protein availability. In particularly, fruit protein increases after infestation with SWD-associated microbes, suggesting that initially-suboptimal intact fruits can become protein-rich on a timeframe that is relevant for larval nutrition. This body of work suggests that microbial associations between flies and their fruit hosts can compensate for the nutritional differences between intact and rotting fruit, and that these relationships are likely responsible for SWD's expanded nutritional niche.
Highlights
Spotted-wing drosophila (SWD), Drosophila suzukii, is a fruit fly species endemic to Eastern and Southeastern Asia [1, 2] but is a recent invasive species in North and South America and Europe [3,4,5,6,7,8,9]
Because the inoculated fruit tissues did not accumulate protein and become more deplete in carbohydrates, the P:C ratio of fruit changed quite quickly. These results suggest that intact fruits that are sub-optimal high-carbohydrate resources at the time of oviposition can quickly become optimal high-protein resources
The synthesis of current research shows that, from a nutritional perspective, the invasion success of SWD is due to interactions between fly physiology, host plant characteristics, and microbial associations that have expanded SWD’s ecological niche in such a way that the pest can utilize novel resources
Summary
Spotted-wing drosophila (SWD), Drosophila suzukii, is a fruit fly species endemic to Eastern and Southeastern Asia [1, 2] but is a recent invasive species in North and South America and Europe [3,4,5,6,7,8,9]. Despite testing different P:C ratios, Young et al [23] and Silva-Soares et al [13] showed that larval survival and developmental times were optimal on more protein-biased diets, which ranged in these studies from a P:C ratio of 1:2 to 24:1.
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