1 Parasitoid gene expression changes after adaptation to symbiont-protected hosts 2 3 Alice B. Dennis,1,2,3,4 Vilas Patel,5 Kerry M. Oliver,5 and Christoph Vorburger1,2 4 1Institute of Integrative Biology, ETH Zürich, Zürich, Switzerland 5 2EAWAG, Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland 6 3Current address: Unit of Evolutionary Biology and Systematic Zoology, Institute of Biochemistry and Biology, University 7 of Potsdam, Potsdam, Germany 8 4E-mail:
[email protected] 9 5Department of Entomology, University of Georgia, Athens, Georgia 30602 10 11 Abstract: 12 Reciprocal selection between aphids, their protective endosymbionts, and the parasitoid wasps that 13 prey upon them offers an opportunity to study the basis of their coevolution. We investigated 14 adaptation to symbiont-conferred defense by rearing the parasitoid wasp Lysiphlebus fabarum on 15 aphids (Aphis fabae) possessing different defensive symbiont strains (Hamiltonella defensa). After 16 ten generations of experimental evolution, wasps showed increased abilities to parasitize aphids 17 possessing the H. defensa strain they evolved with, but not aphids possessing the other strain. We 18 show that the two symbiont strains encode different toxins, potentially creating different targets 19 for counter-adaptation. Phenotypic and behavioral comparisons suggest that neither life history 20 traits nor oviposition behavior differed among evolved parasitoid lineages. In contrast, 21 comparative transcriptomics of adult female wasps identified a suite of differentially expressed 22 genes among lineages, even when reared in a common, symbiont-free, aphid host. In concurrence 23 with the specificity of each parasitoid lineages’ infectivity, most differentially expressed parasitoid 24 transcripts were also lineage-specific.