Chemical cues from competitors change the oviposition preference of Drosophila suzukii

Abstract

Although Drosophila suzukii Matsumura (Diptera: Drosophilidae) infests fresh and ripening fruits, it is attracted to fermented fruits as well. Because fermented fruits attract other flies too, if D. suzukii utilizes fermented fruits as oviposition substrates, competition can be more intense on them. To avoid such competition, D. suzukii may change oviposition preference when particular species of competitor flies are present, but the effect of odor cues associated with competitors on the oviposition preference of D. suzukii is still unknown. To examine such effect, we investigated the oviposition preference of D. suzukii in the presence of four competitor fly species, Drosophila melanogaster Meigen, Drosophila lutescens Malloch, Drosophila rufa Kikkawa & Peng, Drosophila auraria Peng, and D. suzukii itself. We prepared artificial substrates with yeast treatment (Y + : yeast supplementation, Y À : control) and competitor fly treatment (F + : pre-inoculated with competitor fly odor, F À : control), and performed two-choice experiments using the substrates with various Y and F treatments. Our results showed that D. suzukii oviposited more eggs on Y + substrates than on Y À substrates when no competitor flies were present and the presence of competitor flies influenced D. suzukii's oviposition preference for yeast-supplemented substrates and its effect changed depending on the competitor fly species. If the presence of competitors around fallen fruits on the ground suppresses D. suzukii's oviposition on the fallen fruits and facilitates the oviposition on non-fermenting substrates in nature, it may drive D. suzukii to use ripening fruits on the tree. Such selective pressure may facilitate the evolution of morphological traits such as a serrated ovipositor in D. suzukii.

Mind the Wound!—Fruit Injury Ranks Higher than, and Interacts with, Heterospecific Cues for Drosophila suzukii Oviposition

“…Shaw et al (2018) [ 5 ] observed that groups of D. suzukii females tend to avoid egg laying on an artificial fly culture medium infested with eggs and larvae of heterospecific Drosophila ( D. melanogaster ). In part, similar observations were made by Kidera et al (2020) [ 6 ], who let different Drosophila species oviposit on an artificial fruit medium (grape juice agar) and subsequently allowed groups of D. suzukii females to make their oviposition choice. Here we argue that the use of an artificial substrate and fly groups in confined spaces can be a serious problem for identifying a hierarchical order of oviposition preferences among different potential host fruit categories.…”

“…Avoidance of heterospecific cues by the fruit pest Drosophila suzukii is currently discussed as a possible mechanism that reduces interspecific competition with faster developing Drosophila spp. [ 5 , 6 ]. Unlike related Drosophila fruit flies (e.g., D. melanogaster ) D. suzukii possesses a strongly sclerotized ovipositor, with which females can pierce the skin of, and lay eggs into, numerous wild and domesticated fruits [ 7 ].…”

Behavioral and Genomic Sensory Adaptations Underlying the Pest Activity ofDrosophila suzukii

“…Both D. suzukii and D. melanogaster display yeast-mediated oviposition preference, with yeast being a major attractant, more so than fruit volatiles, for D. melanogaster ( Becher et al. 2012 ), and D. suzukii exhibiting competition dependent yeast attraction, choosing to oviposit in substrates without yeast only when other species are present ( Kidera and Takahashi 2020 ).…”

Behavioral and genomic sensory adaptations underlying the pest activity ofDrosophila suzukii

“…This lack of behavioral difference despite clear differences in ripe vs. rotten fruit oviposition preference may be due to the key role of yeast, which converts fruit sugars to ethanol during fermentation, in guiding natural oviposition preference. Both D. suzukii and D. melanogaster display yeast-mediated oviposition preference, with yeast being a major attractant, more so than fruit volatiles, for D. melanogaster (Becher et al, 2012), and D. suzukii exhibiting competition dependent yeast attraction, choosing to oviposit in substrates without yeast only when other species are present (Kidera and Takahashi, 2020). Figure 2E, S2D, supplementary file 2).…”