Genomic analyses of the southern and eastern yellowjacket wasps (Hymenoptera: Vespidae) reveal evolutionary signatures of social life

The evolution of sociality in insects represented a remarkable development
in biological history. Social wasps are particularly noteworthy because
they display gradations in social behaviors. Here, we sequence the genomes
of two highly diverged Vespula wasps to gain greater insight into the
evolution of sociality. Both V. squamosa and V. maculifrons Buysson
(Hymenoptera: Vespidae) are highly social wasps and live in large colonies
characterized by distinct caste systems. However, V. squamosa is a
facultative social parasite, and V. maculifrons is its frequent host. We
found that the genomes of both species were ~200 Mbp in size, similar to
the sizes of congeneric species. Analyses of gene expression from members
of different castes and developmental stages revealed similarities in
expression patterns among immature life stages. Next, we found evidence of
DNA methylation within the genome of both species directly from PacBio
HiFi DNA sequence reads. Patterns of gene expression were correlated with
DNA methylation levels within genes; genes that were highly and uniformly
expressed were also relatively highly methylated. Finally, we uncovered
evidence of differences in patterns of molecular evolution in the two
taxa, consistent with V. squamosa showing changes in selective constraint
associated with its facultatively parasitic or polygyne life history.
Moreover, rates of gene evolution were correlated with variation in gene
expression between castes and developmental stages, as expected if more
highly expressed genes were subject to stronger levels of selection.
Overall, this study expands our understanding of genomic consequences of
social evolution in insects. Keywords: Social Insects, Genetics, Behavior,
Population Genetics, Vespidae Entomological Society of America Editorial
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