Effects of repeated thermic and antibiotic treatments on a Trichogramma (Hym., Trichogrammatidae) symbiont

Each individual of all populations of the thelytokous species Trichogramma cordubensis is infected by Wolbachia . Populations are composed of females, a few rare males and some intersexual or gynandromorphic individuals often capable of normal reproduction as females. Antibiotic (minocycline) and high temperature (30°C) treatments inactivate Wolbachia and induce male production. After these treatments, the sex ratio depending on the remaining frequency of thelytoky shows a genetic variability. Effect of cycles with and without treatments (minocycline or 30°C) on the thelytokous reproduction of ‘individuals’ (one ‘individual’ being one Trichogramma + n Wolbachia ) was studied. The resistance of thelytokous reproduction to 30°C but not to minocycline, probably due to Wolbachia genes, increased. It is concluded that potentialities of adaptation to high temperature exist in Wolbachia and can explain a part of the spreading of these symbionts among host populations.