Selection pressures from pathogens appear to play an important role in shaping social evolution. Social behavior, in particular brood care, is associated with pathogen pressure in wood-dwelling "lower" termites. Yet, generally pathogen pressure is predicted to be low in wood-dwelling termite species that never leave the nest except for the mating flight. In comparison, pathogen pressure is predicted to be higher in species that leave the nest to forage, and thus constantly encounter a diversity of microbes from their environment. We hypothesized that such differences in predicted pathogen pressure are also reflected by differences in the intensity of natural selection on immune genes. We tested this hypothesis in a phylogenetic framework, analyzing rates of non-synonymous and synonymous substitutions on single-copy immune genes. Therefore, we leveraged recent genomic and transcriptomic data from eight termite species, representing wooddwelling and foraging species as well as 14 additional species spanning the winged insects (Pterygota). Our results provide no evidence for a role of pathogen pressure in selection intensity on single-copy immune genes. Instead, we found evidence for a genome-wide pattern of relaxed selection in termites.

The English grain aphid, Sitobion avenae, is a major agricultural pest of wheat, barley and oats, and one of the principal vectors of Barley Yellow Dwarf Virus (BYDV) leading to significant reductions in grain yield, annually. Emerging resistance to and increasing regulation of insecticides has resulted in limited options for their control. Using PacBio HiFi data, we have produced a high quality draft assembly of the S. avenae genome; generating a primary assembly with a total assembly size of 475.7 Mb, and an alternate assembly with a total assembly size of 430.8 Mb. Our primary assembly was highly contiguous with only 326 contigs and a contig N50 of 15.95 Mb. Assembly completeness was estimated at 97.7% using BUSCO analysis and 31,007 and 29,037 protein coding genes were predicted from the primary and alternate assemblies, respectively. This assembly, which is to our knowledge the first for an insecticide resistant clonal lineage of English grain aphid, will provide novel insight into the molecular and mechanistic determinants of resistance and will facilitate future research into mechanisms of viral transmission and aphid behavior.

It has been hypothesized that selection pressure from pathogens plays an important role in shaping social evolution. Social behaviour, in particular brood care, is associated with pathogen pressure in wood-dwelling “lower” termites. Yet, generally pathogen pressure is low in wood-dwelling termite species that never leave the nest except for the mating flight. In comparison, pathogen pressure is higher in species that leave the nest to forage, and thus constantly encounter a diversity of microbes from their environment. We hypothesized that such differences in pathogen pressure are also reflected by differences in the intensity of natural selection on immune genes. We tested this hypothesis in a phylogenetic framework, analyzing rates of non-synonymous and synonymous substitutions on single-copy immune genes. Therefore, we leveraged recent genomic and transcriptomic data from eight termite species, representing wood-dwelling and foraging species as well as 14 additional species spanning the winged insects (Pterygota). Our results provide no evidence for a role of pathogen pressure in selection intensity on single-copy immune genes. Instead, we found evidence for a genome-wide pattern of relaxed selection in termites.Life Science Identifiers (as available Zoobank)Ephemera danica:urn:lsid:zoobank.org:act:06633F75-4809-4BB3-BDCB-6270795368D5Coptotermes sp.urn:lsid:zoobank.org:pub:D6724B7F-F27A-47DC-A4FC-12859ECA0C71Blattella germanica:rn:lsid:zoobank.org:pub:1EA126BA-E9D2-4AA6-8202-26BA5B09B8ADLocusta migratoriaurn:lsid:zoobank.org:pub:D792A09E-844A-412A-BFCA-5293F8388F8CPeriplaneta americana (Blatta americana):urn:lsid:zoobank.org:act:95113A55-4C6D-4DC7-A0E5-620BACADFFE5Apis mellifera:urn:lsid:zoobank.org:act:9082C709-6347-4768-A0DC-27DC44400CB2Bombyx mori (Phalæna (Bombyx) mori)urn:lsid:zoobank.org:act:215466E3-E77F-46E9-8097-372837D7A375Drosophila melanogaster:urn:lsid:zoobank.org:act:5B39F0AA-270D-4AA8-B9A3-C36A3A265910