Synergies Between Division of Labor and Gut Microbiomes of Social Insects

Abstract

Social insects maximize resource acquisition and allocation through division of labor and associations with microbial symbionts. Colonies divide labor among castes and subcastes, where the plasticity of caste roles decreases in clades with higher social grades. Recent studies indicate that specific castes may also foster distinct gut microbiomes, suggesting synergies between division of labor and symbiosis. The social organization of a colony potentially partitions evolutionary persistent microbial partners to optimize symbioses and complement division of labor. However, research in this area has received limited attention. To elucidate if a structured microbiota is adaptive, we present three testable predictions to address consistent community structure, beneficial functions, and selection for microbiota that support caste roles. First, we posit that social insect groups spanning lower to higher social grades exhibit increasingly distinct caste microbiomes, suggesting that structured microbiomes may have evolved in parallel to social complexity. Second, we contend that the development of these microbiomes during colony maturation may clarify the extent to which they support division of labor. Third, we predict that mature social insect colonies with the most extreme division of labor demonstrate the strongest distinctions between caste microbiomes, carrying the greatest promise of insight into microbiome composition and function. Ultimately, we hypothesize that caste-specific microbiomes may enhance symbiotic benefits and the efficiency of division of labor, consequently maximizing fitness.

Genome reduction and relaxed selection is associated with the transition to symbiosis in the basidiomycete genus Podaxis

“…One NRPS (also in bold) was only predicted from two of the termite specialist strains. ll OPEN ACCESS iScience 24, 102680, June 25, 2021 iScience Article that variation in the symbiotic gut microbiota among castes of superorganismal insect colonies may be analogous to the variation in microbiota observed between tissues or body regions of multicellular organisms (Sinotte et al, 2020). Our results indicate a similar analogy between apparently obligate fungal symbionts living within a superorganismal insect colony and the bacterial endosymbionts of non-superorganismal insects.…”

Inter- and Intra-Species Diversity of Lactic Acid Bacteria in Apis mellifera ligustica Colonies

“…However, as also evidenced by other authors [ 71 , 72 , 73 ], to identify the causes and consequences of intra-species diversity, experimental and phenotypic data must be linked to each biotype profile. Moreover, with our knowledge, only few studies [ 74 , 75 ], if any, link the biotype’s diversity to specific ecological niches in honey bee foragers. On this basis, the main important scientific result obtained in our study was the finding that the specific biotypes, through their metabolic profile, contribute to the correct physiology of the associated honey bee organs or to the definition of beebread features.…”

Microbiome structure of a wildDrosophilacommunity along tropical elevational gradients and comparison to laboratory lines

“…Hammer et al, (2019) raised compelling points about bacterial microbiome functionality and demonstrated multiple invertebrate species that appear to have no resident gut microbiome. In other insect species, host transmission of extracellular symbionts (like those in the gut) have been hypothesised to result in long-term associations between insect and microbe (Sanders et al, 2014;Kwong et al, 2017;Sinotte et al, 2020). The long-term laboratory survival of these four Drosophila species (minimum 24 generations) with radically different microbiome composition compared to the field suggests that they do not fit the hypothesis of long-term association between host and microbe, nor that their symbiotic relationship with bacteria is highly specialised (Leftwich et al, 2017).…”