Physiological cost induced by the maternally-transmitted endosymbiont Wolbachia in the Drosophila parasitoid Leptopilina heterotoma

F. FLEURY a1c1, F. VAVRE a1, N. RIS a1, P. FOUILLET a1 and M. BOULÉTREAU a1
a1 Laboratoire de Biométrie et Biologie Évolutive, UMR CNRS 5558, Université Claude Bernard Lyon I, Villeurbanne F69622, France


Endosymbiotic bacteria of the genus Wolbachia infect a number of invertebrate species in which they induce various alterations in host reproduction, mainly cytoplasmic incompatibility (CI). In contrast to most other maternally transmitted parasites, manipulation of host reproduction makes the spread of Wolbachia possible even if they induce a physiological cost on their hosts. Current studies have shown that fitness consequences of Wolbachia infection could range from positive (mutualist) to negative (parasitic) but, in most cases, Wolbachia do not have strong deleterious effects on host fitness and the status of association remains unclear. Here, we show that in the Drosophila parasitoid wasp Leptopilina heterotoma, Wolbachia infection has a negative impact on several host fitness traits of both sexes. Fecundity, adult survival and locomotor performance are significantly reduced, whereas circadian rhythm, development time and offspring sex-ratio are not affected. Although the cost of bacterial infection can be overcome by effects on host reproduction i.e. cytoplasmic incompatibility, it could influence the spread of the bacterium at the early stages of the invasion process. Clearly, results underline the wide spectrum of phenotypic effects of Wolbachia infection and, to our knowledge, Wolbachia infection of L. heterotoma appears to be one of the most virulent that has ever been observed in insects.

(Received January 19 2000)
(Revised April 26 2000)
(Accepted April 30 2000)

Key Words: endosymbiosis; host–parasite evolution; virulence; Wolbachia; cytoplasmic incompatibility; fitness traits.

c1 Corresponding author: Laboratoire de Biométrie et Biologie Evolutive, UMR CNRS 5558, Université Claude Bernard Lyon I, 43 Bd du 11 Novembre 1918, 69622 Villeurbanne Cedex France. Tel: +33 4 72 43 19 21. Fax: 33 4 78 89 27 19. E-mail: