Polyandry and sperm use in the invasive species Ceratitis capitata.

The medfly, Ceratitis capitata, is one of the most destructive agricultural insect pests. It is a polyphagous tepritid species which from its home range in East Africa, has spread to the Mediterranean area, the Americas and Australia. The medfly mating system, is based on arboreal leks, where females encounter several courting males and freely select a mate. Female remating has been reported under laboratory conditions and open field situations. The extent of medfly remating may affect a wide range of evolutionary processes such as sperm competition and sperm use with implications for gene flow and genetic diversity. From an applied perspective, different levels of polyandry may locally have an effect on the efficacy of the Sterile Insect Technique (SIT) which is currently the most commonly applied control strategy against medfly. The availability of high resolution molecular markers such as SSRs coupled with sound statistical tests and simulated estimates allowed us to infer that 1) the level of polyandry may vary among populations and 2) in presence of remating one male, the last one, tends to sire most of the progeny (p2 = 0.8) This paternity advantage is a consequence of second male sperm precedence: the sperm from the second male are utilised four times more with respect to those from the first male. These sperm precedence data are discussed in the light of possibile mechanisms of use and storage.