Diet hierarchies guide temporal-spatial variation in Drosophila suzukii resource use

Authors: Stockton, Dara; LOEB, GREGORY - Cornell University

Submitted to: Frontiers in Ecology and Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/20/2021
Publication Date: 2/1/2022
Citation: Stockton, D.G., Loeb, G.M. 2022. Diet hierarchies guide temporal-spatial variation in Drosophila suzukii resource use. Frontiers in Ecology and Evolution. 9. Article 816557. https://doi.org/10.3389/fevo.2021.816557.
DOI: https://doi.org/10.3389/fevo.2021.816557

Interpretive Summary: Spotted-wing drosophila (SWD) is a major pest of berry crops in the United States. To better understand which crops and wild plants are a potential infestation risk we studied female host use dynamics over time. We tested two things. First, we asked whether preferences could shift towards a certain host plant if that was all that was available in a given area. This is important because host plants vary in different locations around the country, and we were concerned that some hosts could be overlooked if not studied over successive generations. When we conducted this test though, we did not find significant differences between groups reared long-term on different diets. Second, we tested how females responded to different host plants given different availability ratios. We compared raspberry (most preferred), with mushroom (middle), and goose manure (least preferred) in single or multiple combinations. We found that while raspberry use was by far greatest, when raspberry was absent, female SWD laid many more eggs in mushroom and manure.This means that even less preferred host plants or substrates could host SWD when other more preferred hosts are unavailable, particularly during the winter when fruit are scarce.

Technical Abstract: Among insects, female oviposition preferences are critical to understanding the evolutionary dynamics between herbivores and hosts. Previous studies have shown than in Drosophila, resource use has a strong genetic basis, although there is evidence that preferences are adaptable given isolation from ancestral hosts. Given the high degree of adaptability and behavioral plasticity of invasive species, we were interested in the mechanisms affecting host preferences of the invasive fruit fly, Drosophila suzukii, which in recent years has developed a nearly global range. We studied the diet hierarchies of D. suzukii using combination of laboratory and field assays designed to assess how female oviposition host choice differs given the availability of, and experience, with different host plants. We found that host preferences did not shift over time and flies reared on two differential, isolated diets up to F12 behaved and performed similarly regardless of diet lineage. Rather, female host choice appeared guided by a fixed hierarchical system of host preferences. Raspberry was more preferred to mushroom, which was more preferred to goose manure. However, if preferred resources were absent, the use of less-preferred resources was compensatory. We suggest that among niche specialists, such as D. suzukii, these hierarchies may support a bet-hedging strategy, rather than multiple-niche polymorphism, allowing for niche separation during periods of increased competition, while maintaining more diverse, ancestral feeding behaviors when preferred resources are scarce.