The Fallacy of Year-Round Breeding in Polyphagous Tropical Fruit Flies (Diptera: Tephritidae): Evidence for a Seasonal Reproductive Arrestment in Bactrocera Species

Abstract

Bactrocera fruit flies are major pests of horticulture in tropical parts of the world and are highly invasive. Able to breed in many different fruit types, and living in hot to warm climates where temperature is not limiting, it is assumed that these flies breed continuously in their native environment. However, Bactrocera are native to monsoonal rainforests, where the mature fruit needed for breeding is largely absent for four to five months a year during the dry season. Reviewing literature and published population graphs of these flies, we argue that there is evidence to suggest that these flies undergo a reproductive arrest during the dry season when breeding hosts are scarce. We believe females stop or limit reproduction through a diapause or quiescence mechanism, so extending their life-span during the unfavourable breeding period. Once through that period they then switch their life-history strategy to focus on reproduction. Evidence is that this behaviour continues in invaded and agricultural systems and is not just restricted to rainforests. We cannot confirm this hypothesis with the information available, but because of its potential significance in managing these pests we urge that targeted research be carried out to confirm or deny the hypothesis.