We surveyed natural populations of E. virens throughout its Europe-wide range for natural parasites, and particularly tested for the presence of intracellular Wolbachia bacteria. Surprisingly, the results indicate that very few E. virens populations support parasite infections.
We also found no evidence for the presence of Wolbachia in the populations screened. The results therefore show that parasitic infections do not play a role in the maintenance of sex in this system.