Philosophical Transactions of the Royal Society B: Biological Sciences最新文献

Colonies of the bacterim Streptomyces coelicolor divide labour between cells that specialize in growth and sporulation and cells that specialize in antibiotic production. This division of labour arises owing to costly chromosome deletions in the antibiotic overproducers. However, the spatial distribution and temporal emergence of these mutations in S. coelicolor colonies remain unknown, or whether mutation frequency-which we liken to the caste ratio in social insects-is phenotypically plastic. To elucidate changes in the proportions of specialized cells (measured as the mutation frequency), we sampled S. coelicolor colonies grown under different conditions. Temporally, mutation frequency increased linearly with colony age and size. Spatially, mutations accumulated disproportionately in the colony centre, despite greater growth and sporulation at the periphery. Exposing colonies to sub-inhibitory concentrations of some antibiotics, a competitive cue in Streptomyces, increased mutation frequencies. Finally, direct competition with other Streptomyces that naturally produce antibiotics increased mutation frequencies, while also increasing spore production. Our findings provide insights into the intrinsic and environmental factors driving division of labour in Streptomyces colonies by showing that mutation frequencies are dynamic and responsive to the competitive environment. These results show that chromosome deletions are phenotypically plastic and suggest that Streptomyces can flexibly adjust their caste ratio.This article is part of the theme issue 'Division of labour as key driver of social evolution'.

Multimember societies often exhibit Division of labour (DoL), where different individuals perform distinct tasks such as brood care, food acquisition and defence. While demand for tasks exists at the group level, assigning them to specific members poses an organizational challenge. I propose the 'Helping Niche Specialization hypothesis' (HeNS hypothesis), which suggests that cues indicating societal demand for tasks along with the current distribution of help, influence individual biases towards specific task preferences. This process may begin during early ontogeny, even before helping behaviours are actively performed. I first introduce the concept of the 'helping niche', a special form of the social niche. Next, I outline procedures central to the HeNS hypothesis, which represent a stepwise process: (i) societal and environmental cues bias individuals towards task preferences, which may arise already during early life, (ii) experience with preferred tasks reinforces these biases, (iii) learning-by-doing enhances task performance, and/or (iv) reduced response thresholds make task execution more likely, leading to (v) differentiation and specialization. Furthermore, I discuss the costs and benefits of specialization, how helping niches may emerge during development, the environmental conditions that favour them, and alternative pathways to DoL.This article is part of the theme issue 'Division of labour as key driver of social evolution'.

Division of labour (DOL) plays a key role across all scales of biological organization, but how its expression varies across contexts is still poorly understood. Here, we measure DOL in a crucial task, colony defence, in a social insect that affords precise experimental control over individual and colony traits, the clonal raider ant (Ooceraea biroi). We find that DOL in defence behaviour emerges within colonies of near-identical workers, likely reflecting variation in individual response thresholds, and that it increases with colony size. Additionally, colonies with pupae show higher defence levels than those without brood. However, we do not find evidence for a behavioural syndrome linking defence with exploration and activity, as previously reported in other systems. By showing how colony composition and size affect group response to potential threats, our findings highlight the role of the social context in shaping DOL.This article is part of the theme issue 'Division of labour as key driver of social evolution'.

The article reviews the long-standing debate on the division of labour in human societies from a sociological perspective. The division of labour is analysed as a secular trend towards increasing specialization on the one hand and as prevailing arrangements of specialization on the other. The dominant view in economics and other social sciences is that division of labour exists in human societies because it is efficient. We cast doubt on this view by discussing objections to the efficiency paradigm. We show that efficiency considerations, while important, are ultimately insufficient to explain both increasing specialization over time and prevailing arrangements of specialization in real life. As a broader framework, we briefly outline an explanatory triad of efficiency, norms and power. Social norms and power relations often complement unclear and ambiguous efficiency and performance criteria, but they can also conflict with principles of efficiency and rationality.This article is part of the theme issue 'Division of labour as key driver of social evolution'.

Division of labour within social groups and the interspecific relationships within mutualisms have traditionally been treated as separate research areas. In this opinion, we align terminologies and concepts between the two fields, by comparing within-group division of labour to the outsourcing of functions in mutualisms. Division of labour and interspecific outsourcing share fundamental similarities. Both are built from specialization of some individuals within the relationship on tasks or functions required for survival, growth and reproduction. Both also generate variable fitness outcomes. A key difference is that mutualisms generally generate direct fitness gain, while benefits from cooperative sociality often accrue from a mix of direct and indirect fitness. Additionally, the levels of physical and physiological specialization within many mutualisms expand far beyond the levels of differentiation seen in cooperative social groups, with the exception of reproductive division of labour. The consideration of between-species outsourcing in the context of division of labour allows expansion of our understanding of both fields and beyond, to consider general principles as drivers of division of labour, and role differences more broadly across levels of complexity.This article is part of the theme issue 'Division of labour as key driver of social evolution'.

Post-Marx, social scientists have tended to define 'labour' as working for others in return for a wage rather than as a harmonious Durkheimian-style interdependency. This mini-review of recent anthropological literature considers whether, in a world where the 'standard employment contract' is dwindling and many are out of work, 'division of labour' has any continuing relevance.This article is part of the theme issue 'Division of labour as key driver of social evolution'.

An important advantage to sociality is division of labour, which is often associated with specialization of group members, such as the polymorphic subcastes of ant workers. Given this advantage, it is puzzling that many social groups do not show clear specialization. Among ants, workers of closely related species have one, two or even three polymorphisms. The degree of specialism of asocial animals depends on environmental variability because specialists will perform poorly in some conditions. Here, we use a numeric model to consider whether the magnitude and type of environmental variability can help to explain the diversity of specialism in cooperative groups. By finding the optimal distribution of group members along a single dimension of specialization for two tasks, we predict when groups should be composed of specialists, generalists, both of these (trimodal) or moderate specialists. Generalism is predicted more when environments are unstable and when task importance-rather than demand-varies but depends on the likelihood that the group can complete all tasks in the range of experienced conditions. The benefit of sociality is strongest in invariable environments and there is selection for redundancy in the workforce, which may explain the widely observed inactivity in social insects.This article is part of the theme issue 'Division of labour as key driver of social evolution'.

The social organization of Damaraland and naked mole-rats is often suggested to resemble the societies of eusocial insects more closely than that of any other vertebrate. Eusocial insects feature queens that hardly contribute to the workforce, and specialized worker castes. However, in Damaraland and naked mole-rats, which live in family groups with a single breeding pair and multiple non-breeding helpers, the work division is still unclear. Previous studies, largely confined to laboratory settings, could not quantify their primary cooperative behaviour, which is digging extensive foraging tunnels. Here, we studied the distribution of workload in 11 wild Damaraland mole-rat groups, using body acceleration loggers to evaluate behavioural time budgets of 86 individuals. We found behavioural differences between breeders and non-breeders that emerged with increases in group size, such that in large groups, breeders spent less time digging, more time resting, and were overall less active than non-breeders. We did not find any indication of a caste system among non-breeders, though the amount of time individuals spent digging varied with age and sex. Overall, the lower contribution by breeders to the group's workload is a pattern rarely observed in other cooperative vertebrates; nevertheless, the lack of evidence for castes suggests that eusociality may be limited to invertebrates.This article is part of the theme issue 'Division of labour as key driver of social evolution'.

Division of Labour (DoL) among group members reflects the pinnacle of social complexity. The synergistic effects created by task specialization and the sharing of duties benefitting the group raise the efficiency of the acquisition, use, management and defence of resources by a fundamental step above the potential of individual agents. At the same time, it may stabilize societies because of the involved interdependence among collaborators. Here, I review the conditions associated with the emergence of DoL, which include the existence of (i) sizeable groups with enduring membership; (ii) individual specialization improving the efficiency of task performance; and (iii) low conflict of interest among group members owing to correlated payoffs. This results in (iv) a combination of intra-individual consistency with inter-individual variance in carrying out different tasks, which creates (v) some degree of mutual interdependence among group members. DoL typically evolves 'bottom-up' without external regulatory forces, but the latter may gain importance at a later stage of the evolution of social complexity. Owing to the involved feedback processes, cause and effect are often difficult to disentangle in the evolutionary trajectory towards structured societies with well-developed DoL among their members. Nevertheless, the emergence of task specialization and DoL may entail a one-way street towards social complexity, with retrogression getting increasingly difficult the more individual agents depend on each other at progressing stages of social evolution.This article is part of the theme issue 'Division of labour as key driver of social evolution'.

Eusocial insects are characterized by reproductive division of labour, with one (or a few) individuals specialized in reproduction (queen and in termites, also a king) and the other individuals performing all other tasks (workers). Among workers, further division of labour can occur. Termites have three main castes: reproductives, comprising a queen and king; morphologically differentiated sterile soldiers; and workers. Task division among workers varies greatly depending on lifestyle and degree of workers' reproductive potential, which varies from totipotency to reproduce up to sterility. In wood-dwelling species, which do not forage outside the nest, all tasks are performed by totipotent workers, comprising multiple-instars with less further division of labour. Foraging species with pluripotent workers also have a multi-instar worker caste, but some division of labour between brood care versus foraging and defence exists. The first task seems mainly to be done by smaller-and potentially younger-instars, while the latter two tasks are performed by larger-and potentially older-workers. The highest degree of division of labour occurs in foraging species with sterile workers. Here, morphological worker castes with defined tasks and age polyethism occur. Comparisons with Metazoa reveal striking similarities with termites concerning gradients in germline/soma differentiation and cell totipotency.This article is part of the theme issue 'Division of labour as key driver of social evolution'.