Abstract:Nests built by eusocial insect species are often complex structures consisting of multiple effectively integrated and functionally distinct substructures. Stigmergy, self-assembly and self-organisation have been proposed as the mechanisms that translate simple individual behaviour into coordinated collective activity. Here, we consider these processes focusing on their implications for the generation of new structures, nest adaptiveness and the evolution of building rules. We discuss in particular how self-org… Show more
“…One also remarks that in nest ( c ) the curvature distribution is more spread along the H axis, and it is extremely similar to the curvature distribution of the random surface ( e ). These results suggest that the construction process is intrinsically noisy and that probabilistic rather than deterministic rules control the building behaviour [39,40]. Figure 6KDE of the frequency of surface mesh elements in the bidimensional space mean curvature ( H )–Gaussian curvature ( Γ ).…”
We present a simple three-dimensional model to describe the autonomous expansion of a substrate whose growth is driven by the local mean curvature of its surface. The model aims to reproduce the nest construction process in arboreal
Nasutitermes
termites, whose cooperation may similarly be mediated by the shape of the structure they are walking on, for example focusing the building activity of termites where local mean curvature is high. We adopt a phase-field model where the nest is described by one continuous scalar field and its growth is governed by a single nonlinear equation with one adjustable parameter
d
. When
d
is large enough the equation is linearly unstable and fairly reproduces a growth process in which the initial walls expand, branch and merge, while progressively invading all the available space, which is consistent with the intricate structures of real nests. Interestingly, the linear problem associated with our growth equation is analogous to the buckling of a thin elastic plate under symmetric in-plane compression, which is also known to produce rich patterns through nonlinear and secondary instabilities. We validated our model by collecting nests of two species of arboreal
Nasutitermes
from the field and imaging their structure with a micro-computed tomography scanner. We found a strong resemblance between real and simulated nests, characterized by the emergence of a characteristic length scale and by the abundance of saddle-shaped surfaces with zero-mean curvature, which validates the choice of the driving mechanism of our growth model.
“…One also remarks that in nest ( c ) the curvature distribution is more spread along the H axis, and it is extremely similar to the curvature distribution of the random surface ( e ). These results suggest that the construction process is intrinsically noisy and that probabilistic rather than deterministic rules control the building behaviour [39,40]. Figure 6KDE of the frequency of surface mesh elements in the bidimensional space mean curvature ( H )–Gaussian curvature ( Γ ).…”
We present a simple three-dimensional model to describe the autonomous expansion of a substrate whose growth is driven by the local mean curvature of its surface. The model aims to reproduce the nest construction process in arboreal
Nasutitermes
termites, whose cooperation may similarly be mediated by the shape of the structure they are walking on, for example focusing the building activity of termites where local mean curvature is high. We adopt a phase-field model where the nest is described by one continuous scalar field and its growth is governed by a single nonlinear equation with one adjustable parameter
d
. When
d
is large enough the equation is linearly unstable and fairly reproduces a growth process in which the initial walls expand, branch and merge, while progressively invading all the available space, which is consistent with the intricate structures of real nests. Interestingly, the linear problem associated with our growth equation is analogous to the buckling of a thin elastic plate under symmetric in-plane compression, which is also known to produce rich patterns through nonlinear and secondary instabilities. We validated our model by collecting nests of two species of arboreal
Nasutitermes
from the field and imaging their structure with a micro-computed tomography scanner. We found a strong resemblance between real and simulated nests, characterized by the emergence of a characteristic length scale and by the abundance of saddle-shaped surfaces with zero-mean curvature, which validates the choice of the driving mechanism of our growth model.
“…Our datings of crown‐Isoptera, concomitant to those putative nests, could fuel the debate around those nests and their significance for the origin of eusociality, although the construction of large mounds is a derived trait, acquired more recently, within termites. Irrespectively of those dubious fossils (Legendre et al ., 2015), nest structures in termites result from advanced cooperation among colony members, revealing highly integrated social systems (Grassé, 1986; Invernizzi & Ruxton, 2019). The capacity to build a nest was probably inherited by the common ancestor of the crown‐Isoptera (Mizumoto & Bourguignon, 2020).…”
Deciphering the timing and tempo of lineage diversification of organisms has greatly benefited from advances in Bayesian phylogenetic analyses using morphological data. Those advances, however, have not been used for termites despite a rich fossil record. Here, we estimate divergence times for living and fossil termites using the fossilized birth–death (FBD) process on a previously published morphological matrix expanded with two new fossils that we describe (see Appendices S1 and S2). Those fossils, based on soldier specimens, are the mid‐Cretaceous mastotermitid Milesitermes engeli gen. et sp. nov., and the Middle Eocene Reticulitermes grimaldii sp. nov. The latter is the oldest occurrence of a Rhinotermitidae soldier and the first termite soldier described from Baltic amber. Our dating estimates provide new stem‐ages and crown‐ages for termites, suggesting older ages than previously thought for several lineages. Importantly, crown‐Isoptera – and, therefore, eusociality – may have arisen approximately 200 Ma. We conclude with further directions to keep improving our understanding of the timing of differentiation in termites.
“…Sensitivity to trail pheromones and other cues are modulated by neurophysiological differences among nestmates and colonies (Mizunami et al, 2010 ; Muscedere et al, 2012 ; Rittschof et al, 2019 ). The evolution of stigmergic processes can be non-linear, as small changes in ecological context or to nestmate sensitivity can result in novel colony-level outcomes (Invernizzi and Ruxton, 2019 ). How colonies are able to use stigmergic regulation to generate adaptive collective behavior amidst uncertainty is a fundamental motivator of this work.…”
In this paper, we introduce an active inference model of ant colony foraging behavior, and implement the model in a series of in silico experiments. Active inference is a multiscale approach to behavioral modeling that is being applied across settings in theoretical biology and ethology. The ant colony is a classic case system in the function of distributed systems in terms of stigmergic decision-making and information sharing. Here we specify and simulate a Markov decision process (MDP) model for ant colony foraging. We investigate a well-known paradigm from laboratory ant colony behavioral experiments, the alternating T-maze paradigm, to illustrate the ability of the model to recover basic colony phenomena such as trail formation after food location discovery. We conclude by outlining how the active inference ant colony foraging behavioral model can be extended and situated within a nested multiscale framework and systems approaches to biology more generally.
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