Mating success, fecundity and fertility of marula fruit fly, Ceratitis cosyra Walker (Diptera: Tephritidae) exposed to simulated heat waves

Anthropogenic activities contribute to more volatile weather conditions, including more frequent heat waves of higher intensity and longer duration. Heat waves may have the potential to change the distribution patterns of pest species, which may relate to the effects of high temperatures on fertility. This study determined the reproductive consequences associated with exposure to heat waves for the marula fruit fly, Ceratitis cosyra (Walker) (Diptera: Tephritidae). Heat waves were represented by five consecutive days of temperatures 5 – 7°C higher than the optimal temperature for development. Female and male C. cosyra, were exposed to four separate temperature treatments (25°C as the control; and 31°C, 34°C and 37°C as heat waves) to evaluate the effects of each temperature on survival over five days (n = 50 for each sex and temperature). Thereafter, females and males exposed to the same temperatures were paired with untreated individuals of the opposite sex to mate (n = 50 for each sex and temperature). This was repeated five times and mating propensity, mating latency, fecundity and fertility were recorded. Heat wave temperatures did not reduce survival when compared with the control. Sex and temperature had no effect on mating propensity. A decrease in mating latency occurred as temperatures increased, with both treated sexes mating slightly earlier at 34°C. Heat-treated females had significantly lower fecundity and fertility than untreated females paired with heat-treated males. Females mated with heat-treated males did not suffer decreased fecundity relative to the control, but fertility tended to decline with temperature. In conclusion, C. cosyra females were more susceptible to increasing heat wave temperatures than males. Results also indicated that fecundity and fertility were the reproductive traits mostly affected in C. cosyra when exposed to heat waves. This research could help to derive more accurate distribution predictions for C. cosyra in a changing climate.