Bugs and drugs and speciation: the impact of symbiotic Wolbachia on Drosophila development, sexual behavior and speciation

The Drosophila paulistorum species complex serves a well-studied model system for evaluating the impact of symbiosis on host speciation since they evolve rapidly and comprise an ancestral, but highly dynamic, reservoir of microbial symbionts. Theory and some experimental evidence suggest that in evolutionary long-term host-symbiont interactions, reproductive parasites might evolve a more benign lifestyle towards mutualism, manipulate sexual mating behavior, and foster host speciation. However, it is an ongoing debate as to whether or not microbial symbionts are capable of driving host speciation in nature and if so, to what extent. Prime candidates are Wolbachia, inherited, endosymbiotic bacteria of many arthropods, presently attracting attention as potential biocontrol agents since they affect host reproductive biology. Here we will document that all D. paulistorum semispecies harbor conspecific but distinctive Wolbachia strains that provide significant fitness benefits such as viability and fecundity to their natural hosts. In semispecies hybrids, however, these naturally obligate mutualists turn into pathogens, triggering embryonic lethality and male sterility. Besides their impact on post-mating isolation, we show that in their native D. paulistorum hosts Wolbachia manipulate sexual behavior by triggering pre-mating isolation via selective mate avoidance, i.e. avoiding mates harboring another, incompatible symbiont variant. Our study reveals that endosymbionts can co-evolve rapidly with their native hosts and play a significant role in host physiology, pheromone expression and sexual behavior, thereby they are capable of driving natural host speciation.

Contact

  David Hughes
  dph14@psu.edu