Coevolutionary motion and swarming in a niche space model of
ecological species interactions |
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Authors: | C J Dommar A Ryabov B Blasius |
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Institution: | (1) Department of Physics, University of Potsdam, 14415 Potsdam, Germany;(2) ICBM, University of Oldenburg, 26111 Oldenburg, Germany |
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Abstract: | Organisms are involved in coevolutionary relationships with their competitors, predators, preys and parasites. In this context,
we present a simple model for the co-evolution of species in a common niche space, where the fitness of each species is defined
via the network of interactions with all other species. In our model, the sign and type of the pairwise interactions (being
either beneficial, harmful or neutral) is given by a pre-determined community matrix, while the interaction strength depends
on the niche-overlap, i.e. the pairwise distances between species in niche space.
The evolutionary process drives the species toward the places with the higher local fitness along the fitness gradient. This
gives rise to a dynamic fitness landscape, since the evolutionary motion of a single species can change the landscape of the
others (known as the Red Queen Principle). In the simplest case of only two-species we observe either a convergence/divergence
equilibrium or a coevolutionary arms race.
For a larger number of species our analysis concentrates on an antisymmetric interaction matrix, where we observe a large
range of dynamic behaviour, from oscillations, quasiperiodic to chaotic dynamics. In dependence of the value of a first integral
of motion we observe either quasiperiodic motion around a central region in niche space or unbounded movement, characterised
by chaotic scattering of species pairs.
Finally, in a linear food-chain we observe complex swarming behaviour in which the swarm moves as a whole only if the chain
consists of an even number of species. Our results could be an important contribution to evolutionary niche theory. |
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