Nest choice in arboreal ants is an emergent consequence of network creation under spatial constraints

Biological transportation networks must balance competing functional
priorities. The self-organizing mechanisms used to generate such networks
have inspired scalable algorithms to construct and maintain low-cost and
efficient human-designed transport networks. The pheromone-based trail
networks of ants have been especially valuable in this regard. Here, we
use turtle ants as our focal system: In contrast to the ant species
usually used as models for self-organized networks, these ants live in a
spatially constrained arboreal environment where both nesting options and
connecting pathways are limited. Thus, they must solve a distinct set of
challenges which resemble those faced by human transport engineers
constrained by existing infrastructure. Here, we ask how a turtle ant
colony’s choice of which nests to include in a network may be influenced
by their potential to create connections to other nests. In laboratory
experiments with Cephalotes varians and Cephalotes texanus, we show that
nest choice is influenced by spatial constraints, but in unexpected ways.
Under one spatial configuration, colonies preferentially occupied more
connected nest sites; however, under another spatial configuration, this
preference disappeared. Comparing the results of these experiments to an
agent-based model, we demonstrate that this apparently idiosyncratic
relationship between nest connectivity and nest choice can emerge without
nest preferences via a combination of self-reinforcing random movement
along constrained pathways and density-dependent aggregation at nests.
While this mechanism does not consistently lead to the de-novo
construction of low-cost, efficient transport networks, it may be an
effective way to expand a network, when coupled with processes of pruning
and restructuring.