Abstract
AbstractAimIn 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.LocationLa Réunion, France, Indian Ocean.MethodsWe 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.ResultsOur 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 conclusionsWe 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.
Highlights
Biological invasions are a major threat to biodiversity (Millennium Ecosystem Assessment (Program), 2005; Murphy & Romanuk, 2014)
We focused on the following points: i) the distribution and host range of this polyphagous species in La Réunion; ii) How the host range has evolved and iii) how the climatic niche of each species changed after this invasion
Our findings reveal two different types of response for Ceratitis species: C. capitata found an ecological refuge in host plants with small berries rarely infested by B. dorsalis, such as Murraya paniculata and Passiflora suberosa, while the C. quilicii host range largely overlaps that of B. dorsalis
Summary
Biological invasions are a major threat to biodiversity (Millennium Ecosystem Assessment (Program), 2005; Murphy & Romanuk, 2014). They can lead to a decrease in gene pools by causing the extinction of native species and alter habitat and ecosystem functions (Simberloff et al, 2013; Vilà et al, 2010). Competitive displacement is generally observed between closely related species. In most cases, it is triggered by the invasion of an exotic species, which displaces an indigenous species or an established exotic species (Reitz & Trumble, 2002). Differential climatic tolerance among competitors can allow species coexistence across environmental gradients (Czárán, 1991)
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