Whole-body transcriptomics of Nasonia vitripennis females as they respond to sex allocation cues

Linking the evolution of the phenotype to the underlying genotype is a key aim of evolutionary genetics and is crucial to our understanding of how natural selection shapes a trait. Here we consider the genetic basis of sex allocation behaviour in the parasitoid wasp Nasonia vitripennis using a transcriptomics approach. Females allocate offspring sex in line with Local Mate Competition (LMC) theory. Female-biased sex ratios are produced when one or few females lay eggs on a patch. As the number of females contributing offspring to a patch increases, less female-biased sex ratios are favoured. We contrasted the transcriptomic responses of females as they oviposit under conditions known to influence sex allocation: foundress number (a social cue) and the state of the host (parasitised or not). We found, that when females encounter other females on a patch, or assess host quality with their ovipositors, the resulting changes in sex allocation is not associated with significant changes in whole-body gene expression. We also found that the gene expression changes produced by females, as they facultatively allocate sex in response to a host cue and a social cue, are very closely correlated. We expanded the list of candidate genes associated with oviposition behaviour in Nasonia, some of which may be involved in fundamental processes underlying the ability to facultatively allocate sex, including sperm storage and utilisation. Overall design: 2 x 3 factorial design. Females were placed into 1 of 2 "foundress number" groups: 1) alone or 2) in the presence of 9 other females (co-foundresses). Females were further subdivided into host treatment groups: i) given no host, ii) given a fresh host and iii) given a pre-parasitised host. This gives a total of 6 possible treatment combinations. For each of these 6 groups, 7 pools of 10 females were sequenced giving 42 libraries altogether.

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Cook N, Trivedi U, Pannebakker BA, Blaxter M, Ritchie MG, Tauber E, Sneddon T, Shuker DM