A well-known pest of fruit crops is the invasive spotted wing drosophila (SWD), which was brought from South-East Asia. By removing the fruit’s skin’s mechanical defenses to lay its eggs, it creates a point of entrance for additional infestation. The fruit rots and becomes unusable as a result of egg deposition and injected bacteria that speed up deterioration. Although this little invasive fruit fly is well recognized for seriously harming agriculture’s economy, less is known about how it affects other natural ecosystems like forests.
According to a recent study by Swiss researchers from the Swiss Federal Institute for Forest, Snow, and Landscape Research (WSL) and the kobüro Biotopia, the SWD competes fiercely with other fruit-eating species and that its presence could have significant effects on ecosystems. The study’s findings were published in the academic journal NeoBiota.
By examining a total of 12,000 fruits for SWD egg deposits, the research team evaluated the utilization of possible host plants at 64 sites in forests from mid-June to mid-October 2020. They also noted fruit degradation symptoms following egg deposition to assess whether SWD attacks are the cause of the condition. They also kept an eye on the local drosophilid (invasive fruit fly) fauna since they thought the SWD would outnumber and maybe outcompete other fruit-eating insects.
Of the 39 fruit-bearing forest plant species the authors evaluated, egg deposits were observed on the fruits of 31 of them, with 18 species exhibiting attack rates greater than 50%. Additionally, after egg deposition, more than 50% of the afflicted plant species exhibited significant decay symptoms. Because they modify the chemical makeup of fruits and alter visual cues like color, shape, and reflected patterns, egg depositions may change how appetizing fruits are. As a result, fruit consumption by seed dispersers like birds may decrease.
There will likely be major ecological effects given the enormous amount of infected fruit. According to Prof. Martin M. Gossner, an entomologist at the WSL, “rapid decay of fruits attacked by the spotted wing drosophila results in a loss of fruit available for other species competing for this resource and may disrupt seed-dispersal mutualisms due to reduced consumption of fruit by dispersers such as birds.” Plants and seed dispersers may suffer if the fly reproduces in huge numbers.
The authors also discovered that SWD were significantly represented and predominated in trap catches, and they demonstrated that the native drosophilid population decreased as SWD increased in abundance. This shows that the invading species has harmed native communities in additional ways.
Since higher average and winter temperatures will likely result in shorter generation times and lower winter mortality, which will eventually increase the pressure on forest fruits and the competitiveness of the SWD over native drosophilids, the authors note that these potentially severe ecological impacts may be amplified in temperate forests as a result of ongoing climate change.
