Exposé Chercheur Invité

Bugs and Drugs and Speciation: The Impact of Mutualistic Wolbachia on Drosophila Development, Sexual Behaviour and Symbiotic Speciation

Wolfgang J. MILLER (Université de Médecine de Vienne, Autriche)

Current standard models of speciation disregard potential impacts of microbial reproductive tract symbionts fostering host speciation. Based on numerous theoretical models but limited experimental data, prime candidates driving symbiotic speciation in arthropods are intracellular bacteria belonging to the genus Wolbachia. They are inherited symbionts of many arthropods capable of manipulating host reproductive biology for their own benefits. However, it is an ongoing debate as to whether or not reproductive symbionts are capable
of triggering host speciation in nature and if so, to what extent.

Hence we applied the classic model system of symbiotic speciation manifest in neotropical Drosophila paulistorum semispecies by means of present-day molecular approaches and artificial symbiont-depletion experiments. This superspecies, consisting of at least six reproductively isolated semispecies, has been the object of attention of an array of researchers since at least 1955, when it was initially trapped mid-evolution in flagrant statu nascendi. In this system it has been proposed that microbial endosymbionts foster incipient speciation.

We have recently demonstrated the α-proteobacteria Wolbachia as the maternally transmitted core endosymbiont of D. paulistorum semispecies that presently foster symbiotic speciation by triggering pre- and postmating isolation mechanisms . Here we will report on

(i) the impact of Wolbachia on driving artificial de novo reproductive isolation in D. paulistorum,

(ii) their effects on host pheromone expression patterns and sexual behaviour, and

(iii) unorthodox transmission modes of mitochondria in hybrids.
Finally we will introduce a second symbiotic speciation system in statu nascendi, i.e., the Glossina morsitans species group of tsetse flies, where conspecific but incompatible Wolbachia infections trigger postmating isolation in nature

Salle Silvolab (Campus de Kourou)

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