Self-organized sorting limits behavioral variability in swarms

Abstract

Swarming is a phenomenon where collective motion arises from simple local interactions between typically identical individuals. Here, we investigate the effects of variability in behavior among the agents in finite swarms with both alignment and cohesive interactions. We show that swarming is abolished above a critical fraction of non-aligners who do not participate in alignment. In certain regimes, however, swarms above the critical threshold can dynamically reorganize and sort out excess non-aligners to maintain the average fraction close to the critical value. This persists even in swarms with a distribution of alignment interactions, suggesting a simple, robust and efficient mechanism that allows heterogeneously mixed populations to naturally regulate their composition and remain in a collective swarming state or even differentiate among behavioral phenotypes. We show that, for evolving swarms, this self-organized sorting behavior can couple to the evolutionary dynamics leading to new evolutionarily stable equilibrium populations set by the physical swarm parameters.

How many dissenters does it take to disorder a flock?

“…It is interesting to compare this critical fraction of dissenters of p 0.01 » to the corresponding value for the finite cohesive flocks studied in [19]. In the latter, considering the limit of large inter-agent cohesiveness, typical values of the critical fraction of dissenters are around p 0.5 (see figure 1 in [19]). This fraction can even be further increased by lowering the cohesiveness, which allows aligners to expel dissenters and reorganize into several flocking clusters.…”

“…Recent work has begun to consider the effect of disorder either present in the environment in the form of physical obstacles to the motion [10][11][12][13][14] or arising from variations in the properties of individual agents or their ability to align with neighbors [15][16][17][18][19]. Both environmental disorder and disruptions in alignment rules were found to destabilize the flocking state, in agreement with observations in bacteria and insect swarms, where a fraction of individuals with a decreased production of signaling compounds or pheromones that promote collective behavior can disrupt organization.…”

Spatial Self-Organization Resolves Conflicts Between Individuality and Collective Migration

“…In microbial communities, maintaining diversity in the population can enable bet-hedging strategies to survive uncertain environments and resolve trade-offs 13,15,16,17,18 . However, heterogeneity can also be disruptive, as is the case in simulated swarms where non-aligners tend to be purged from the swarm 19 . This raises a dilemma: although phenotypic diversity provides advantages, it also tends to reduce coordination.…”

Collective motion as a distinct behavioural state of the individual

“…Our findings reported here suggest that, in locusts, the sensory-motor act of Considerable research has been devoted in recent years to understanding the effect of variability among individuals on the group's collective behavior, both experimentallyranging from bacteria to primates [24][25][26][27][28][29][30][31][32][33] -and theoretically [34][35][36][37][38][39][40] ; (see [41][42][43] for recent reviews).…”