Conserved Genes Underlie Phenotypic Plasticity in an Incipiently Social Bee

Abstract

Despite a strong history of theoretical work on the mechanisms of social evolution, relatively little is known of the molecular genetic changes that accompany transitions from solitary to eusocial forms. Here, we provide the first genome of an incipiently social bee that shows both solitary and social colony organization in sympatry, the Australian carpenter bee Ceratina australensis. Through comparative analysis, we provide support for the role of conserved genes and cis-regulation of gene expression in the phenotypic plasticity observed in nest-sharing, a rudimentary form of sociality. Additionally, we find that these conserved genes are associated with caste differences in advanced eusocial species, suggesting these types of mechanisms could pave the molecular pathway from solitary to eusocial living. Genes associated with social nesting in this species show signatures of being deeply conserved, in contrast to previous studies in other bees showing novel and faster-evolving genes are associated with derived sociality. Our data provide support for the idea that the earliest social transitions are driven by changes in gene regulation of deeply conserved genes.

Sociality emerges from solitary behaviours and reproductive plasticity in the orchid beeEuglossa dilemma

“…This is, in part, because molecular studies of insect sociality have been conducted primarily on advanced eusocial species (such as honeybees and ants), leaving the basis of simpler social behaviour relatively understudied [4]. Consequently, investigation of the mechanisms enabling social behaviour in species that form small, flexible social groups may be especially informative, providing unique opportunities to test hypotheses about the evolution of social behaviour [5].…”

Genetic signatures of dominance hierarchies reveal conserved cis‐regulatory and brain gene expression underlying aggression in a facultatively social bee

“…Approximately 4% of the reads were removed from the libraries after adapter removal and quality filtering (% surviving reads). Paired-end reads were aligned to the C. australensis genome 31 using TopHot2 after quality filtering. 32…”

“…Averaged normalized read counts were used to construct heatmaps with the R package heatmap.2 in gplot (version 2.12.1). Functional annotation of genes was extracted from the C. australensis genome 31 and GO ontology enrichment was performed on DEGs upregulated in each of the four behavioral categories using a Fisher's exact test on the R package topGO for cellular functions, biological processes, and molecular functions 34 (version 2.3). Resulting P-values were then adjusted for multiple testing using the method of Benjamini and Hochberg 35 for calculating false discovery rate.…”

“…This includes corto (upregulated in maintained rank and losers) which is upregulated in C. calcarata that maintain rank as well as those who are consistently losers, and ETS98b which is upregulated primarily in subordinates of both C. australensis and Apis mellifera. 31,49 Significantly enriched GO terms in C. australensis were compared to seven different studies related to aggression, dominance, and social structure, representing eight different species (Tables S3 and S5). We found that the broadest overlap occurred in metabolic genes (GO:0005975-carbohydrate metabolic process, GO:0019538-protein metabolic process; Table S3); with additional overlap in GO terms enriched for defense response (GO:0006952) and immune function (GO:0002376-immune system process, GO:0045087-innate immune response; Table S3).…”

The molecular basis of socially-mediated phenotypic plasticity in a eusocial paper wasp

“…By comparing the gene expression profiles of groups of individuals that differ in their phenotypes as a result of plasticity, it is possible to isolate phenotypic effects of gene expression while controlling for genetic differences. Using this approach, significant progress has been made in unravelling the molecular underpinnings of sequential sex changes in hermaphroditic fish (Horiguchi et al 2013;Casas et al 2016;Todd et al 2019), the distinct gregarious social phenotype of desert locusts (Cullen et al 2017;Lo et al 2018), and the reproductive castes of social insects (Simola et al 2016;Libbrecht et al 2018;Rehan et al 2018;Shell & Rehan 2018). Such studies typically rely on comparisons between groups of individuals with well-differentiated phenotypes, however.…”