RT Journal Article SR Electronic T1 Wolbachia and host intrinsic reproductive barriers contribute additively to post-mating isolation in spider mites JF bioRxiv FD Cold Spring Harbor Laboratory SP 2020.06.29.178699 DO 10.1101/2020.06.29.178699 A1 Cruz, Miguel A. A1 Magalhães, Sara A1 Sucena, Élio A1 Zélé, Flore YR 2020 UL http://biorxiv.org/content/early/2020/11/14/2020.06.29.178699.abstract AB Wolbachia are widespread maternally-inherited bacteria suggested to play a role in arthropod host speciation through induction of cytoplasmic incompatibility, but this hypothesis remains controversial. Most studies addressing Wolbachia-induced incompatibilities concern closely-related populations, which are intrinsically compatible. Here, we used three populations of two genetically differentiated colour forms of the haplodiploid spider mite Tetranychus urticae to dissect the interaction between Wolbachia-induced and host-associated incompatibilities, and to assess their relative contribution to post-mating isolation. We found that these two sources of incompatibility act through different mechanisms in an additive fashion. Host-associated incompatibility contributes 1.5 times more than Wolbachia-induced incompatibility in reducing hybrid production, the former through an overproduction of haploid sons at the expense of diploid daugters (ca. 75% decrease) and the latter by increasing the embryonic mortality of daughters (by ca. 49%). Furthermore, regardless of cross direction, we observed nearcomplete F1 hybrid sterility and complete F2 hybrid breakdown between populations of the two forms, but that Wolbachia did not contribute to this outcome. This study identifies the mechanistic independence and additive nature of host-intrinsic and Wolbachia-induced sources of isolation. It suggests that Wolbachia could drive reproductive isolation in this system, thereby potentially affecting host differentiation and distribution in the field.Competing Interest StatementThe authors have declared no competing interest.CIcytoplasmic incompatibilitywCIWolbachia-induced cytoplasmic incompatibilityHIHost-associated incompatibilityEMEmbryonic mortalityFMFemale mortalityMDMale developmentJMJuvenile mortalityFPFemale proportion over total number of eggs laidSRSex ratio (here ratio of females to males in the offspring).