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 hig h temperature (30 degrees C) treatments inactivate Wolbachia and induce mal e production. After these treatments, the sex ratio depending on the remain ing frequency of thelytoky shows a genetic variability. Effect of cycles wi th and without treatments (minocycline or 30 degrees C) on the thelytokous reproduction of 'individuals' (one 'individual' being one Trichogramma +n W olbachia) was studied. The resistance of thelytokous reproduction to 30 deg rees 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 am ong host populations.