Niche shift of tephritid species after the oriental fruit fly (Bactrocera dorsalis) invasion in La Réunion.
Aim: In a context of successive fruit fly invasions (Tephritidae), this study investigated how the top invader, Bactrocera dorsalis, displaced established fruit fly populations. We focused, particularly, on how this invasion impacted the host range and climatic niche of each resident species. Location: La Réunion, France, Indian Ocean. Methods: We collected fruit from more than 100 plant species across the island, in cultivated and non-cultivated areas at different altitudes in order to monitor the emergence of fruit flies. Fruit collection was conducted over two field campaigns: from 2001 to 2009, before the B. dorsalis invasion; and from 2018 to 2019, after the B. dorsalis invasion. We compared the distribution and host range of fruit fly species for the two periods. Results: Our results confirmed the generalist character of B. dorsalis, with the infestation of 52 out of 112 of the fruit species collected in the field. After the B. dorsalis invasion, we observed a shift in the host range and spatial distribution of established tephritids. The host range of specialist species that only share a few host species with B. dorsalis did not change significantly. On the contrary, we observed a significant shift in diversity or proportion of host range and climatic niches for the generalist species, such as Bactrocera zonata, Ceratitis quilicii and Ceratitis capitata. Main conclusions: We provide evidence of the competitive displacement induced by B. dorsalis on other established species. The coexistence between B. dorsalis and generalist Ceratitis species seems possible because they have different responses to climatic conditions or the capacity to exploit other host fruit species. In contrast, the coexistence of B. zonata with B. dorsalis seems to be compromised because both species have similar ecological requirements. This research provides useful information for managing invasions, particularly since understanding competitive displacements is essential for the identification of empty niches and for modelling potential species distribution.