Worker Personality and Its Association with Spatially Structured Division of Labor

<div><p>Division of labor is a defining characteristic of social insects and fundamental to their ecological success. Many of the numerous tasks essential for the survival of the colony must be performed at a specific location. Consequently, spatial organization is an integral aspect of division of labor. The mechanisms organizing the spatial distribution of workers, separating inside and outside workers without central control, is an essential, but so far neglected aspect of division of labor. In this study, we investigate the behavioral mechanisms governing the spatial distribution of individual workers and its physiological underpinning in the ant <i>Myrmica rubra.</i> By investigating worker personalities we uncover position-associated behavioral syndromes. This context-independent and temporally stable set of correlated behaviors (positive association between movements and attraction towards light) could promote the basic separation between inside (brood tenders) and outside workers (foragers). These position-associated behavior syndromes are coupled with a high probability to perform tasks, located at the defined position, and a characteristic cuticular hydrocarbon profile. We discuss the potentially physiological causes for the observed behavioral syndromes and highlight how the study of animal personalities can provide new insights for the study of division of labor and self-organized processes in general.</p></div

Spatial fidelity of <i>M. rubra</i> workers within colonies.

<p>Presented is the proportion of scans a worker of a given origin (O = outside, E = entrance, B = brood and Q = queen) was detected at the one of the four monitored locations during experiment 1. Presented are medians and quartiles, circles indicate outliers. Significant differences between the positions (p<0.0001) are indicated by different lower case letters on top of the figure.</p

We present the differences between the five analyzed CHC substance classes (left to right).

<p>Proportion of the five substance classes. Median and quartiles are presented. Significant differences between the four groups investigated (B = brood, O = outside, Q = queen, E = Entrance) are indicated by the lower-case letters on top of the individual graphs (all significant p<0.003; ns = no significant difference). Circles indicate outliers.</p

MDS ordination of the worker personality dimensions (2D stress = 0.11), based on euclidian distances.

<p>Each symbol represents an individual worker. Lines indicate the contribution of each behavioral trait to the separation among the three groups investigated (B = brood, O = outside and E = entrance). All three groups are significantly different from each other (all p<0.007). The three main contributors to group separation are phototactic (Experiment 3a), activity (3c) and brood-care tendency (3f). The interest in protein foraging (3e), exploration (3b), non-nestmates (3d) and aggression (3g) contributed to a lesser extent.</p