Sequential invasions by fruit flies (Diptera: Tephritidae) in Pacific and Indian Ocean islands: A systematic review

Abstract

The aim of our review was to examine the cases of Tephritidae invasions across island systems in order to determine whether they follow a hierarchical mode of invasion. We reviewed the literature on factors and mechanisms driving invasion sequences in Pacific and Southwest Indian Ocean islands and gathered every record of invasion by a polyphagous tephritid in island groups. From invasion date or period, we defined an invasion link when a new fruit fly established on an island where another polyphagous tephritid is already resident (that was indigenous or a previous invader). Across surveyed islands, we documented 67 invasion links, involving 24 tephritid species. All invasion links were directional, i.e., they involved a series of invasions by invaders that were closely related to a resident species but were increasingly more competitive. These sequential establishments of species are driven by interspecific competition between resident and exotic species but are also influenced by history, routes, and flows of commercial exchanges and the bridgehead effect. This information should be used to improve biosecurity measures. Interactions between trade flow, invasive routes, and the presence of invasive and resident species should be integrated into large-scale studies.

Keywords: biosecurity; exotic species; human‐mediated dispersal; interspecific competition; patterns of invasion.

FIGURE 1

Invasion among 15 Pacific territories by polyphagous fruit flies. For each territory, the sequence of circles extends from indigenous species (when present) on the right to invasive species to the left, with 1st‐, 2nd‐, 3rd‐, and 4th‐order invaders in temporal sequence from right to left using invasion date or period from Appendix S1. Some species were eradicated after introduction (such as B. dorsalis in Nauru and in Australia) but represent successful cases of invasion of one polyphagous species in the presence of another polyphagous species

FIGURE 2

Invasion of eight islands in the Southwest Indian Ocean by polyphagous fruit flies. For each territory, the sequence of circles extends from indigenous species (when present) on the right to invasive species to the left, with 1st‐, 2nd‐, 3rd‐, and 4th‐order invaders in temporal sequence from right to left using invasion date or period from Appendix S1

FIGURE 3

Diagram of the invasion links among polyphagous tephritids from Appendix S1. Each link represents a successful invasion by one species in the presence of another species. The number in brackets for each invasive species represents the number of invasions observed in the presence of another polyphagous species