Evolutionary mechanisms of insecticide resistance in the Mediterranean fruit fly Ceratitis capitata (Wiedmann)

The Mediterranean fruit fly (medfly) Ceratitis capitata is one of the most invasive agricultural pests worldwide. It is highly polyphagous and causes considerable economic losses in fruit production. Despite environmental concerns, chemical control remains the most important strategy used in medfly pest management. The most frequently used pesticides belong to organophosphorus and carbamates. Both classes target acetyl-cholinesterase (AChE), a key enzyme in the nervous system of insects, and inhibit its activity. Intensive applications of such pesticides generated a widespread resistance due to well-established aminoacid changes in the enzyme. Although the mechanism of resistance is now well known, this has not been translated into better understanding of its origin (recurrent versus single) and its spread and maintenance across the large geographic range and diverse environmental conditions. In order to study the genetic variation related to insecticide resistance, several medfly specimens were collected from various regions worldwide, such as: Tunisia, Spain, Greece, Guatemala, South Africa and Australia. A marker system has been developed to assess nucleotide variation affecting various regions of the medfly genome, using restriction–site associated DNA (RAD) tags. In addition, coalescence methods and phylogenetic reconstruction were used to evaluate neutral processes of population divergence and expansion vs. non-neutral processes driven by pesticides. Insecticide resistance is useful for the study of evolutionary change. The analysis of genomic variation in population of a worldwide pest such as C. capitata can provide a picture of how local and global factors determine the future of lineages under climate change and increased globalization.