Molecular and behavioral studies reveal differences in olfaction between winter and summer morphs of Drosophila suzukii

Abstract

Spotted-wing drosophila, Drosophila suzukii (Matsumura), is a major economic pest of several fruit crops in Europe, North and South America, and other parts of the world because it oviposits in ripening thin-skinned fruits. This vinegar fly exhibits two distinct morphotypes: a summer and a winter morph. Although adaptations associated with the winter morph enhance this invasive pest’s capacity to survive in cold climates, winter is still a natural population bottleneck. Since monitoring early spring populations is important for accurate population forecasts, understanding the winter morph’s response to olfactory cues may improve current D. suzukii management programs. In this study, a comparative transcriptome analysis was conducted to assess gene expression differences between the female heads of the two D. suzukii morphs, which showed significant differences in 738 genes ( p ≤ 0.0001). Out of twelve genes related to olfaction determined to be differentially expressed in the transcriptome, i.e. , those related to location of food sources, chemosensory abilities, and mating behavior, nine genes were upregulated in the winter morph while three were downregulated. Three candidate olfactory-related genes that were most upregulated or downregulated in the winter morph were further validated using RT-qPCR. In addition, behavioral assays were performed at a range of temperatures to confirm a differing behavioral response of the two morphs to food odors. Our behavioral assays showed that, although winter morphs were more active at lower temperatures, the summer morphs were generally more attracted to food odors. This study provides new insights into the molecular and behavioral differences in response to olfactory cues between the two D. suzukii morphs that will assist in formulating more effective monitoring and physiological-based control tools.

Winter Is (Not) Coming: Is Climate Change Helping Drosophila suzukii Overwintering?

“…Additionally, monitoring traps are less efficient during the winter, which could be associated with differences in the response to volatiles between SM and WM [55]. Schwanitz et al (2022) found several differentially expressed genes between SM and WM associated with the olfactory behavior of D. suzukii, namely those linked to food-seeking and mating behaviors, reinforcing previous work that suggested that WM flies have different food preferences than SM [56,57]. Considering that the flies surviving the winter are the most concerning at the beginning of the fruiting season [21], it is essential to understand these transcriptomic differences between SM and WM, to develop management practices targeted at WM flies and therefore reduce the impact of the winter survivors on the first fruits.…”

The contrasting role of climate variation on the population dynamics of a native and an invasive insect pest

“…trapping data for the northeast USA show very few captures of D. suzukii adults during the winter compared with those during summer months [62], which is a pattern that could be due to lower population sizes but also to lower adult activity and a lack of response to volatile cues from traps by the winter compared with that of the summer morphs [63]. Nevertheless, we expect that greater numbers of overwintering D. suzukii adults could result in larger populations in the spring because of a greater likelihood of overwinter survival, leading to earlier trap captures, in contrast with Briem et al [64].…”

Does the seasonal phenotype of Drosophila suzukii influence cellular immunity and parasitisation?

“…Adults of the winter phenotype have a longer lifespan at lower temperatures, have larger and darker bodies (Shearer et al., 2016; Wallingford & Loeb, 2016) and enter a temperature‐dependent reproductive diapause (Rossi‐Stacconi et al., 2016; Toxopeus et al., 2016; Zerulla et al., 2015). Furthermore, comparisons of the two phenotypes showed that the winter phenotype has an overexpression of detoxification genes in response to insecticides (Seong et al., 2022) and the summer morphs have a higher attraction to food odours (Schwanitz et al., 2022). The winter phenotype is adapted to colder conditions and is, therefore, the dominant phenotype at lower temperatures.…”