1,970 research outputs found
A food chain ecoepidemic model: infection at the bottom trophic level
In this paper we consider a three level food web subject to a disease
affecting the bottom prey. The resulting dynamics is much richer with respect
to the purely demographic model, in that it contains more transcritical
bifurcations, gluing together the various equilibria, as well as persistent
limit cycles, which are shown to be absent in the classical case. Finally,
bistability is discovered among some equilibria, leading to situations in which
the computation of their basins of attraction is relevant for the system
outcome in terms of its biological implications
Spreading of families in cyclic predator-prey models
We study the spreading of families in two-dimensional multispecies
predator-prey systems, in which species cyclically dominate each other. In each
time step randomly chosen individuals invade one of the nearest sites of the
square lattice eliminating their prey. Initially all individuals get a
family-name which will be carried on by their descendants. Monte Carlo
simulations show that the systems with several species (N=3,4,5) are
asymptotically approaching the behavior of the voter model, i.e., the survival
probability of families, the mean-size of families and the mean-square distance
of descendants from their ancestor exhibit the same scaling behavior. The
scaling behavior of the survival probability of families has a logarithmic
correction. In case of the voter model this correction depends on the number of
species, while cyclic predator-prey models behave like the voter model with
infinite species. It is found that changing the rates of invasions does not
change this asymptotic behavior. As an application a three-species system with
a fourth species intruder is also discussed.Comment: to be published in PR
Severe population collapses and species extinctions in multi-host epidemic dynamics
Most infectious diseases including more than half of known human pathogens
are not restricted to just one host, yet much of the mathematical modeling of
infections has been limited to a single species. We investigate consequences of
a single epidemic propagating in multiple species and compare and contrast it
with the endemic steady state of the disease. We use the two-species
Susceptible-Infected-Recovered (SIR) model to calculate the severity of
post-epidemic collapses in populations of two host species as a function of
their initial population sizes, the times individuals remain infectious, and
the matrix of infection rates. We derive the criteria for a very large,
extinction-level, population collapse in one or both of the species. The main
conclusion of our study is that a single epidemic could drive a species with
high mortality rate to local or even global extinction provided that it is
co-infected with an abundant species. Such collapse-driven extinctions depend
on factors different than those in the endemic steady state of the disease
On the critical behavior of the Susceptible-Infected-Recovered (SIR) model on a square lattice
By means of numerical simulations and epidemic analysis, the transition point
of the stochastic, asynchronous Susceptible-Infected-Recovered (SIR) model on a
square lattice is found to be c_0=0.1765005(10), where c is the probability a
chosen infected site spontaneously recovers rather than tries to infect one
neighbor. This point corresponds to an infection/recovery rate of lambda_c =
(1-c_0)/c_0 = 4.66571(3) and a net transmissibility of (1-c_0)/(1 + 3 c_0) =
0.538410(2), which falls between the rigorous bounds of the site and bond
thresholds. The critical behavior of the model is consistent with the 2-d
percolation universality class, but local growth probabilities differ from
those of dynamic percolation cluster growth, as is demonstrated explicitly.Comment: 9 pages, 5 figures. Accepted for publication, Physical Review
Persistence of complex food webs in metacommunities
Metacommunity theory is considered a promising approach for explaining
species diversity and food web complexity. Recently Pillai et al. proposed a
simple modeling framework for the dynamics of food webs at the metacommunity
level. Here, we employ this framework to compute general conditions for the
persistence of complex food webs in metacommunities. The persistence conditions
found depend on the connectivity of the resource patches and the structure of
the assembled food web, thus linking the underlying spatial patch-network and
the species interaction network. We find that the persistence of omnivores is
more likely when it is feeding on (a) prey on low trophic levels, and (b) prey
on similar trophic levels
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