Fig. 1
Diagram of experimental crosses and their outcomes. a Interspecific crosses of Nasonia vitripennis and N. longicornis strains R3 and UT produce F1 hybrids prior to 2008. b An asymmetric, postzygotic F1 hybrid lethality arises between N. vitripennis strains and N. longicornis strain R3 but not with N. longicornis strain UT. c To test if this asymmetric hybrid lethality is due to a maternal genetic or cytoplasmic effect, heterozygous offspring of N. longicornis (UT/R3 and R3/UT) were crossed with N. vitripennis, resulting in approximately 50% survival of F1 hybrid female offspring with both genotypes and cytotypes, indicating the hybrid incompatibility is not due to the R3 cytotype. d To further test the maternal genetic effect on hybrid mortality, N. longicornis strains UT and R3 were reciprocally backcrossed to each other, resulting in ~99.8% genome replacement into the alternative line’s cytotype. Females of these strains were then mated with N. vitripennis males, resulting in the same F1 hybrid lethality observed when the R3 genome was in a UT cytotype (IntR3/UT) but not when the UT genome was in the R3 cytotype (IntUT/R3)