Bipartite network analysis of ant-task associations reveals task groups and absence of colonial daily activity

Abstract

Social insects are one of the best examples of complex self-organized systems exhibiting task allocation. How task allocation is achieved is the most fascinating question in behavioural ecology and complex systems science. However, it is difficult to comprehensively characterize task allocation patterns due to behavioural complexity, such as the individual variation, context dependency and chronological variation. Thus, it is imperative to quantify individual behaviours and integrate them into colony levels. Here, we applied bipartite network analyses to characterize individual-behaviour relationships. We recorded the behaviours of all individuals with verified age in ant colonies and analysed the individual-behaviour relationship at the individual, module and network levels. Bipartite network analysis successfully detected the module structures, illustrating that certain individuals performed a subset of behaviours (i.e. task groups). We confirmed age polyethism by comparing age between modules. Additionally, to test the daily rhythm of the executed tasks, the data were partitioned between daytime and nighttime, and a bipartite network was re-constructed. This analysis supported that there was no daily rhythm in the tasks performed. These findings suggested that bipartite network analyses could untangle complex task allocation patterns and provide insights into understanding the division of labour.

Reproductive potentials of task-shifting workers in a queenless ant

“…We set oocyte length as the response variable, worker task as the fixed effect, and colony ID as the random effect. To examine the effects of fixed effects, we performed Type II analysis of variance using the Anova function of the "car" package (Fox and Weisberg 2019) to compare the constructed models with the null models. For post hoc analysis, the significance level was adjusted using the Bonferroni method (P = 0.05/3).…”