Data from: “Darwin’s corollary” and cytoplasmic incompatibility induced by Cardinium may contribute to speciation in Encarsia wasps (Hymenoptera: Aphelinidae)

The potential importance of cytoplasmic incompatibility (CI) – inducing
bacterial symbionts in speciation of their arthropod hosts has been
debated. Theoretical advances have led to a consensus that a role is
plausible when CI is combined with other isolating barriers. However, the
insect model systems Nasonia and Drosophila are the only two experimental
examples documented. Here we analyzed the components of reproductive
isolation between the parasitoid wasp Encarsia suzannae, which is infected
by the CI-inducing symbiont Cardinium, and its uninfected sibling species
Encarsia gennaro. Laboratory crosses demonstrated that: 1) sexual
isolation is incomplete; 2) hybrid offspring production is greatly reduced
in the interspecific CI cross; 3) viable hybrids may be produced by curing
E. suzannae males of Cardinium with antibiotics; 4) hybrid offspring
production in the reciprocal cross is greatly reduced by hybrid
inviability due to genetic incompatibilities; 5) hybrid sterility is
nearly complete in both directions at the F1 stage. Thus, asymmetrical
hybrid incompatibilities and CI act as complementary isolating mechanisms.
We propose a new model for contributions of CI symbionts to speciation,
with CI reducing gene flow between species in one direction, and in the
other, a symbiont sweep resulting in accelerated mtDNA evolution, negative
cytonuclear interactions and hybrid incompatibilities.