No evidence for immune-gene specific signals of selection in termites

Meusemann, Karen; Korb, Judith; Schughart, Maximilian; Staubach, Fabian

doi:10.1101/783738

Cited by 1 publication

(2 citation statements)

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“…Therefore, it is possible to observe pervasive relaxed selection without a reduction in N e , given a change in s that affects many loci. Previous authors have hypothesized that the cooperative interactions of social species can buffer or compensate for the expression of deleterious mutations, particularly in relation to immune responses [41][42][43][44][45][46]. The creation of a benign environment through social cooperation (e.g., termite mounds) and/or the compensating for the expression of deleterious alleles (e.g., through food allocation) will lead to a reduction in selection pressures for the genes involved [46].…”

Section: (D) Alternative Explanations For Relaxed Selection In Termit...mentioning

confidence: 99%

“…Hence, if pervasive relaxed selection were caused by a reduced we might expect relaxed selection to be restricted to one or two of the termite species, or observe comparable levels of relaxed selection in some cockroach species (e.g., Periplaneta americana, a recently urbanized cockroach species, sister lineage to the termite species in our analysis). Second, if a reduced s across many genes were due to the social benefits of group living (e.g., allogrooming), we might expect a larger overlap of orthologues to be under relaxed selection (Figure 1d; but see [43]), and a larger proportion of orthologues under relaxed selection in the termite ancestral branches.…”

Section: (D) Alternative Explanations For Relaxed Selection In Termit...mentioning

confidence: 99%

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Pervasive relaxed selection in termite genomes

Ewart,

Ho,

Chowdhury

et al. 2023

Preprint

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The genetic changes that enabled the evolution of eusociality have long captivated biologists. In recent years, attention has focussed on the consequences of eusociality on genome evolution. Studies have reported higher molecular evolutionary rates in eusocial hymenopteran insects compared with their solitary relatives. To investigate the genomic consequences of eusociality in termites, we sequenced genomes from three of their non-eusocial cockroach relatives. Using a phylogenomic approach, we found that termite genomes experienced lower rates of synonymous mutations than those of cockroaches, possibly as a result of longer generation times. We identified higher rates of nonsynonymous mutations in termite genomes than in cockroach genomes, and identified pervasive relaxed selection in the former (24–31% of the genes analysed) compared with the latter (2–4%). We infer that this is due to a reduction in effective population size, rather than gene-specific effects (e.g., indirect selection of caste-biased genes). We found no obvious signature of increased genetic load in termites, and postulate efficient purging at the colony level. Additionally, we identified genomic adaptations that may underpin caste formation, such as genes involved in post-translational modifications. Our results provide insights into the evolution of termites and the genomic consequences of eusociality more broadly.

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