Foraging behaviour variations, for gene expression and transcriptomic divergence in parasitic wasp populations of Venturia canescens

Foraging behaviours encompass strategies to locate resources and to
exploit them. In many taxa, these behaviours are driven by a major gene
called for, but mechanisms vary between species. In the parasitoid wasp
Venturia canescens, sexual and asexual populations coexist in sympatry but
differ in life-history trait, physiology and behaviours, which could
impact their foraging strategies. Here, we explored the molecular bases
underpinning divergence in behaviours by testing two mutually nonexclusive
hypotheses: first, the divergence in the for gene correlates with
difference in foraging strategies, and second, the latter rely on a
divergence in whole-genome expression. Using comparative genomics, we
showed that the for gene was conserved across insects considering both
sequence and gene model complexity. Polymorphism analysis did not support
the occurrence of two allelic variants diverging across the two
populations, yet the asexual population exhibited less polymorphism than
the sexual population. Sexual and asexual transcriptomes sharply split,
with 10.9% of differentially expressed genes, but these were not enriched
in behavioural-related genes. We showed that the for gene was more highly
expressed in asexual female heads than in sexual heads and that those
differences correlate with divergence in foraging behaviours in our
experiment since asexuals explored the environment more and exploited more
host patches. Overall, these results suggested that fine tuning of for
gene expression between populations may have led to distinct foraging
behaviours. We hypothesized that reproductive polymorphism and coexistence
in sympatry of sexual and asexual populations specialized to different
ecological niches via divergent optima on phenotypic traits could imply
adaptation through different expression patterns of the for gene and at
many other loci throughout the genome.