Evolution of predator-prey systems described by a Lotka-Volterra equation under random environment. (English) Zbl 1113.34042

Takeuchi, Y.; Du, N. H.; Hieu, N. T.; Sato, K.

J. Math. Anal. Appl. 323, No. 2, 938-957 (2006).

Consider random 2D Lotka-Volterra systems
\[ \dot{x} = x (a(\xi_t)-b(\xi_t)y) , \quad \dot{y} = y (-c(\xi_t)+d(\xi_t)x) \]
for the size \(x\) of prey and \(y\) of predators, where \(a,b,c,d : E \to \mathbb R_+ \setminus \{0\}\) and the Markov process \(\xi\) has two states \(E=\{1,2\}\) only. Suppose that \(\xi\) jumps at times which have conditionally independent, exponentially distributed increments. It is proved that, under the influence of so-called telegraph noise \(\xi\), all positive trajectories of such a system always go out from any compact set of \(\mathbb R_{+}^{2}\) with probability one if two rest points of the two systems do not coincide. In case where they have the rest point in common, the trajectory either leaves from any compact set of \(\mathbb R_{+}^{2}\) or converges to the rest point. The escape of the trajectories from any compact set means ecologically that the system is neither permanent nor dissipative.
The authors extend investigations of Slatkin (1978) in 1D to 2D, known from ecology. Some simulation results are presented as well. For the probabilistic proofs, they use well-known techniques of 0-1 laws.

Reviewer: Henri Schurz (Carbondale)

MSC:

34F05	Ordinary differential equations and systems with randomness
37H10	Generation, random and stochastic difference and differential equations
60H10	Stochastic ordinary differential equations (aspects of stochastic analysis)
92D25	Population dynamics (general)
92D40	Ecology

Keywords:

predator-prey model; telegraph noise; dissipativity; permanence; persistency; 0-1 laws; Markov chains; long term behavior

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