Fallen fruit: A backup resource during winter shaping fruit fly communities

Abstract

Abstract Fallen fruits provide important feeding and breeding substrates for insects such as Drosophilidae and can be a potential trophic reservoir when usual host fruits become scarce. Recently, two invasive fruit fly species, Drosophila suzukii and Chymomyza amoena, have become established in Europe and are expected to alter existing Drosophilidae communities. In this study, carried out between September 2021 and April 2022 in northern France, we aimed to disentangle the relative roles of microclimatic, landscape and local factors driving the diversity of the Drosophilidae community in decaying fruit across seasons. Minimum site temperature during the week preceding sampling and the proportion of rotten fruit tissue had the strongest positive influence on Drosophilidae abundance and species richness. Drosophilidae abundance also increased with urbanisation (portion of building cover) around the sampled trees. Decaying apples were important breeding sites for C. amoena across seasons, but provided a suboptimal substrate for D. suzukii, which was only present in late summer. This study sheds light on the important role of unharvested fallen crop fruit in maintaining the diversity of an insect family that is generally overlooked in field studies. It also emphasises the importance of considering multiple scales and factors when studying the interactions between invasive species, native species and their shared trophic resources. Finally, our data highlight the importance of the Drosophilidae community in recycling agricultural waste.