Host-virus evolutionary dynamics with specialist and generalist infection strategies: bifurcations, bistability and chaos

TL;DR

This paper models the evolutionary dynamics of viruses evolving between specialist and generalist strategies, revealing conditions for stability, coexistence, and chaos through bifurcation analysis.

Contribution

It introduces a nonlinear mathematical model analyzing bifurcations, stability, and chaos in host-virus evolution with both specialist and generalist strains.

Findings

Identification of stable equilibria and periodic orbits.

Conditions leading to bistability and coexistence.

Detection of chaotic dynamics and bifurcation points.

Abstract

In this work we have investigated the evolutionary dynamics of a generalist pathogen, e.g. a virus population, that evolves towards specialisation in an environment with multiple host types. We have particularly explored under which conditions generalist viral strains may rise in frequency and coexist with specialist strains or even dominate the population. By means of a nonlinear mathematical model and bifurcation analysis, we have determined the theoretical conditions for stability of nine identified equilibria and provided biological interpretation in terms of the infection rates for the viral specialist and generalist strains. By means of a stability diagram we identified stable fixed points and stable periodic orbits, as well as regions of bistability. For arbitrary biologically feasible initial population sizes, the probability of evolving towards stable solutions is obtained for each point of the analyzed parameter space. This probability map shows combinations of infection rates of the generalist and specialist strains that might lead to equal chances for each type becoming the dominant strategy. Furthermore, we have identified infection rates for which the model predicts the onset of chaotic dynamics. Several degenerate Bogdanov-Takens and zero-Hopf bifurcations are detected along with generalized Hopf and zero-Hopf bifurcations. This manuscript provides additional insights into the dynamical complexity of host-pathogen evolution towards different infection strategies.