Can host reproduction number inform the invasion potential of Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), into endemic Queensland fruit fly, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), areas in southeaster

Abstract The competitive displacement of one tephritid species by another tephritid is much discussed but not well understood. In south-eastern Australia, Bactrocera tryoni is speculated to have competitively displaced Ceratitis capitata by 1953. Here, I compared the host reproduction number (HRN) in 37 host fruit for B. tryoni and C. capitata to calculate a reproductive advantage (RA) for each fruit fly. I found 17 hosts where the RA favoured C. capitata but this number declined after tropical hosts were removed from the list. There were four hosts with RA > 10. Regarding the RA for B. tryoni , I found 20 hosts favouring B. tryoni (12 with RA > 10) with several commonly grown hosts at the time of displacement. I speculate that HRN and RA may partly explain why B. tryoni displaced C. capitata. The possible role of other tephritids in the displacement of C. capitata could not be assessed due to lack of HRN data.