Lysiphlebus fabarum; experimental evolution; clones; Aphis fabae; parasitoids; aphids; transcriptomics; Antagonistic coevolution; Hamiltonella defensa; endosymbionts; resistance
(2016), Are aphid parasitoids locally adapted to the prevalence of defensive symbionts in their hosts?, in BMC evolutionary biology
, 16(1), 271-271.
(2016), Bacterial endosymbionts protect aphids in the field and alter parasitoid community composition, in ECOLOGY
, 97(7), 1712-1723.
(2015), Cheaper isn't always worse: Strongly protective isolates of a defensive symbiont are less costly to the aphid host, in Proceedings of the Royal Society London B
, 282, 20142333.
(2015), Genetic and morphological variation in sexual and asexual parasitoids of the genus Lysiphlebus - an apparent link between wing shape and reproductive mode, in BMC EVOLUTIONARY BIOLOGY
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(2015), Sugar-feeding behaviour and longevity of European Culicoides biting midges., in Medical and veterinary entomology
, 29, 17-25.
(2015), Symbiont-conferred protection against Hymenopteran parasitoids in aphids: how general is it?, in Ecological Entomology
, 40, 85-93.
(2014), Biased Transmission of Sex Chromosomes in the Aphid Myzus persicae Is Not Associated with Reproductive Mode, in PLOS ONE
, 9(12), e116348.
(2014), Experimental evolution of parasitoid infectivity on symbiont-protected hosts leads to the emergence of genotype specificity., in Evolution; international journal of organic evolution
, 68(6), 1607-16.
(2014), The evolutionary ecology of symbiont-conferred resistance to parasitoids in aphids., in Insect science
, 21(3), 251-64.
(2014), Thelytoky and sex determination in the hymenoptera: mutual constraints., in Sexual development : genetics, molecular biology, evolution, endocrinology, embryology, and patholog
, 8(1-3), 50-8.
, Faithful vertical transmission but ineffective horizontal transmission of bacterial endosymbionts during sexual reproduction of the black bean aphid, Aphis fabae, in Ecological Entomology
, Population Genetic Issues: New Insights Using Conventional Molecular markers and Genomics Tools.
Antagonistic coevolution between hosts and parasites is a driving force behind many important evolutionary phenomena, including the maintenance of genetic polymorphism. An increasing number of studies report that hosts may rely on 'helpers' in the form of microbial endosymbionts for defence against parasites. This challenges our current understanding of host-parasite coevolution that is based on models assuming direct interactions between host and parasite."Symbiont-mediated coevolution in an insect host-parasitoid system" is the first large-scale project to explicitly address how defensive symbionts affect the coevolution between hosts and parasites. In the first three years of the project we have developed new mathematical models that account for resistance provided by defensive symbionts and describe the expected dynamics of such symbiont-mediated coevolution, and we have investigated this process empirically, using a study system comprising the black bean aphid, Aphis fabae, its bacterial endosymbiont Hamiltonella defensa, and the aphid parasitoid Lysiphlebus fabarum. Our work has shown that host infection with H. defensa strongly modifies the reciprocal selection between aphids and parasitoids. While the aphids' own defences are relatively weak and general, the resistance conferred by symbionts is strong and acts much more specifically, but it is also associated with costs such as a reduced lifespan. These are the conditions under which our models predict that the symbionts may take over from the hosts the coevolutionary arms race against the parasites. In our study system, parasitoids do indeed harbour ample genetic variation for the ability to overcome symbiont-conferred resistance, and they can adapt rapidly to the presence of defensive symbionts in their hosts. However, we also found that different counteradaptations are required to break resistance by different strains of H. defensa. Overall, the project has demonstrated unambiguously that endosymbionts play a crucial role in host-parasite coevolution.Despite the progress we made, open questions remain. It is still unknown whether more protective strains of H. defensa are also more costly to the host, which would help explain the maintenance of the observed variation in this symbiont, and we lack a mechanistic understanding of parasitoid counteradaptations to symbiont-conferred resistance. These issues will be addressed by the research proposed for a two-year extension of my SNF Professorship. We till test experimentally for a trade-off between host protection and costs to the host by quantifying these effects for multiple isolates of H. defensa within the same genetic backgrounds. We will further investigate whether parasitoids have evolved the ability to suppress their host's defensive symbionts, and we will try to identify the genes involved in parasitoid counteradaptations. For this we will take advantage of recent advances in whole-transcriptome sequencing (RNA-Seq) and apply this technique to compare gene expression between parasitoids selected for an improved ability to parasitize symbiont-protected hosts and unselected controls. Given that resistance conferred by symbionts is a feature of many host-parasite interactions, the proposed research will represent an important step towards a better understanding of host-parasite coevolution. I also expect this work to yield applied benefits, because aphid parasitoids are frequently used for biological control of pest aphids. Host resistance conferred by defensive symbionts compromises the efficiency of biological control. Our work on parasitoid counteradaptations is therefore timely and will help to develop more effective biocontrol agents.