Patterns of Positive Selection in Seven Ant Genomes

Abstract

The evolution of ants is marked by remarkable adaptations that allowed the development of very complex social systems. To identify how ant-specific adaptations are associated with patterns of molecular evolution, we searched for signs of positive selection on amino-acid changes in proteins. We identified 24 functional categories of genes which were enriched for positively selected genes in the ant lineage. We also reanalyzed genome-wide data sets in bees and flies with the same methodology to check whether positive selection was specific to ants or also present in other insects. Notably, genes implicated in immunity were enriched for positively selected genes in the three lineages, ruling out the hypothesis that the evolution of hygienic behaviors in social insects caused a major relaxation of selective pressure on immune genes. Our scan also indicated that genes implicated in neurogenesis and olfaction started to undergo increased positive selection before the evolution of sociality in Hymenoptera. Finally, the comparison between these three lineages allowed us to pinpoint molecular evolution patterns that were specific to the ant lineage. In particular, there was ant-specific recurrent positive selection on genes with mitochondrial functions, suggesting that mitochondrial activity was improved during the evolution of this lineage. This might have been an important step toward the evolution of extreme lifespan that is a hallmark of ants.

Adaptive evolution of animal proteins over development: support for the Darwin selection opportunity hypothesis of Evo-Devo

“…In order to characterize the signal of positive selection, we used the log-likelihood ratio test statistic (∆lnL) of H 1 to H 0 models with or without positive selection, from the branch-site model (Zhang et al 2005) as precomputed in Selectome on filtered alignments , and as used in (Roux et al 2014;Daub et al 2017).…”

Transcriptomics and neuroanatomy of the clonal raider ant implicate an expanded clade of odorant receptors in chemical communication

“…A long-standing debate in the field of sociogenomics is the importance of conserved genes vs. novel genes in social evolution (2,3). Researchers have tried to address this question primarily by either looking for signatures of positive selection associated with the evolution of sociality (43,44) or by looking for genes that are differentially expressed between different morphological and behavioral castes (45,46). An alternative approach is to find genes with specific functions in social behavior and to examine their evolution.…”

Rapid expansion of immune-related gene families in the house fly,Musca domestica

“…Numerous studies have reported that genes encoding proteins in the insect immune response are exceptionally likely to evolve by repeated positive selection (Schlenke and Begun 2003;Sackton et al 2007;Lazzaro 2008;Obbard et al 2009;Keebaugh and Schlenke 2012;Roux et al 2014); here, we focus particularly on rates of gene gain and loss. Several lines of evidence suggest that the M. domestica immune response is unusual, at least when compared with the standard Dipteran model D. melanogaster.…”