The Susceptibility of Mediterranean (MED) Species to Attack by a Parasitoid Wasp Changes between Two Whitefly Strains with Different Facultative Endosymbiotic Bacteria.

In this study, two strains of the mitochondrial lineage Q1 of MED species, characterized by a different complement of facultative bacterial endosymbionts, were tested for their susceptibility to be attacked by the parasitoid wasp , a widespread natural enemy of . Notably, the BtHC strain infected with and was more resistant to parasitization than the BtHR strain infected with and . The resistant phenotype consisted of fewer nymphs successfully parasitized (containing the parasitoid mature larva or pupa) and in a lower percentage of adult wasps emerging from parasitized nymphs. Interestingly, the resistance traits were not evident when parasitism was compared between BtHC and BtHR using parasitoids originating from a colony maintained on BtHC. However, when we moved the parasitoid colony on BtHR and tested after it was reared on BtHR for four and seven generations, we saw then that BtHC was less susceptible to parasitization than BtHR. On the other hand, we did not detect any difference in the parasitization of the BtHR strain between the three generations of tested. Our findings showed that host strain is a factor affecting the ability of to parasitize and lay the basis for further studies aimed at disentangling the role of the facultative endosymbiont and of the genetic background in the resistance of MED to parasitoid attack. Furthermore, they highlight that counteradaptations to the variation of defence mechanisms may be rapidly selected in to maximize the parasitoid fitness.