Intransitivity and coexistence in four species cyclic games

Intransitivity is a property of connected, oriented graphs representing species interactions that may drive their coexistence even in the presence of competition, the standard example being the three species Rock-Paper-Scissors game. We consider here a generalization with four species, the minimum number of species allowing other interactions beyond the single loop (one predator, one prey). We show that, contrary to the mean field prediction, on a square lattice the model presents a transition, as the parameter setting the rate at which one species invades another changes, from a coexistence to a state in which one species gets extinct. Such a dependence on the invasion rates shows that the interaction graph structure alone is not enough to predict the outcome of such models. In addition, different invasion rates permit to tune the level of transitiveness, indicating that for the coexistence of all species to persist, there must be a minimum amount of intransitivity.Comment: Final, published versio

Chaotic attractors in Atkinson-Allen model of four competing species

We study the occurrence of chaos in the Atkinson-Allen model of four competing species, which plays the role as a discrete-time Lotka-Volterra-type model. We show that in this model chaos can be generated by a cascade of quasiperiod-doubling bifurcations starting from a supercritical Neimark-Sacker bifurcation of the unique positive fixed point. The chaotic attractor is contained in a globally attracting invariant manifold of codimension one, known as the carrying simplex. Biologically, our study implies that the invasion attempts by an invader into a trimorphic population under Atkinson-Allen dynamics can lead to chaos.Peer reviewe

On the dynamics of multi-species Ricker models admitting a carrying simplex

We study the dynamics of the Ricker model (map) T. It is known that under mild conditions, T admits a carrying simplex , which is a globally attracting invariant hypersurface of codimension one. We define an equivalence relation relative to local stability of fixed points on the boundary of Σ on the space of all 3D Ricker models admitting carrying simplices. There are a total of 33 stable equivalence classes. We list them in terms of simple inequalities on the parameters, and draw each one's phase portrait on Σ. Classes 1-18 have trivial dynamics, i.e. every orbit converges to some fixed point. Each map from classes 19-25 admits a unique positive fixed point with index -1, and Neimark-Sacker bifurcations do not occur in these 7 classes. In classes 26-33, there exists a unique positive fixed point with index 1. Within each of classes 26 to 31, there do exist Neimark-Sacker bifurcations, while in class 32 Neimark-Sacker bifurcations can not occur. Whether there is a Neimark-Sacker bifurcation in class 33 or not is still an open problem. Class 29 can admit Chenciner bifurcations, so two isolated closed invariant curves can coexist on the carrying simplex in this class. Each map in class 27 admits a heteroclinic cycle, i.e. a cyclic arrangement of saddle fixed points and heteroclinic connections. As the growth rate increases the carrying simplex will break, and chaos can occur for large growth rate. We also numerically show that the 4D Ricker map can admit a carrying simplex containing a chaotic attractor, which is found in competitive mappings for the first time.Peer reviewe

Chaotic attractors in the four-dimensional Leslie-Gower competition model

We study the occurrence of the chaotic attractor in the four-dimensional classical Leslie-Gower competition model. We find that chaos can be generated by a cascade of quasiperiod-doubling bifurcations starting from a supercritical Neimark-Sacker bifurcation of the positive fixed point in this model. The chaotic attractor is contained in the three-dimensional carrying simplex, that is a globally attracting invariant manifold. Biologically, the result implies that the invasion attempts by an invader into a trimorphic population under the Leslie-Gower dynamics can lead to chaos. (C) 2019 Elsevier B.V. All rights reserved.Peer reviewe

Global stability and repulsion in autonomous Kolmogorov systems

Criteria are established for the global attraction, or global repulsion on a compact invariant set, of interior and boundary fixed points of Kolmogorov systems. In particular, the notions of diagonal stability and Split Lyapunov stability that have found wide success for Lotka-Volterra systems are extended for Kolmogorov systems. Several examples from theoretical ecology and evolutionary game theory are discussed to illustrate the results

Robust permanence for interacting structured populations

The dynamics of interacting structured populations can be modeled by $\frac{dx_i}{dt}= A_i (x)x_i$ where $x_i\in \R^{n_i}$, $x=(x_1,\dots,x_k)$, and $A_i(x)$ are matrices with non-negative off-diagonal entries. These models are permanent if there exists a positive global attractor and are robustly permanent if they remain permanent following perturbations of $A_i(x)$. Necessary and sufficient conditions for robust permanence are derived using dominant Lyapunov exponents $\lambda_i(\mu)$ of the $A_i(x)$ with respect to invariant measures $\mu$. The necessary condition requires $\max_i \lambda_i(\mu)>0$ for all ergodic measures with support in the boundary of the non-negative cone. The sufficient condition requires that the boundary admits a Morse decomposition such that $\max_i \lambda_i(\mu)>0$ for all invariant measures $\mu$ supported by a component of the Morse decomposition. When the Morse components are Axiom A, uniquely ergodic, or support all but one population, the necessary and sufficient conditions are equivalent. Applications to spatial ecology, epidemiology, and gene networks are given

On the Stabilizing Effect of Predators and Competitors on Ecological Communities

Ecological communities can lose their permanence if a predator or a competitor is removed: the remaining species no linger coexist. This well known phenomenon is analyzed for some low dimensional examples of Lotka-Volterra type, with special attention paid to the occurrence of heteroclinic cycles