2,755 research outputs found
Predation effects on mean time to extinction under demographic stochasticity
Methods for predicting the probability and timing of a species' extinction
are typically based on a combination of theoretical models and empirical data,
and focus on single species population dynamics. Of course, species also
interact with each other, forming more or less complex networks of
interactions. Models to assess extinction risk often lack explicit
incorporation of these interspecific interactions. We study a birth and death
process in which the death rate includes an effect from predation. This
predation rate is included via a general nonlinear expression for the
functional response of predation to prey density. We investigate the effects of
the foraging parameters (e.g. attack rate and handling time) on the mean time
to extinction. Mean time to extinction varies by orders of magnitude when we
alter the foraging parameters, even when we exclude the effects of these
parameters on the equilibrium population size. In particular we observe an
exponential dependence of the mean time to extinction on handling time. These
findings clearly show that accounting for the nature of interspecific
interactions is likely to be critically important when estimating extinction
risk.Comment: 11 pages, 4 figures; Typos removed. For further discussion about the
paper go to http://purl.org/net/extinctio
The conflict interaction between two complex systems. Cyclic migration
We construct and study a discrete time model describing the conflict
interaction between two complex systems with non-trivial internal structures.
The external conflict interaction is based on the model of alternative
interaction between a pair of non-annihilating opponents. The internal conflict
dynamics is similar to the one of a predator-prey model. We show that the
typical trajectory of the complex system converges to an asymptotic attractive
cycle. We propose an interpretation of our model in terms of migration
processes
Community-driven dispersal in an individual-based predator-prey model
We present a spatial, individual-based predator-prey model in which dispersal
is dependent on the local community. We determine species suitability to the
biotic conditions of their local environment through a time and space varying
fitness measure. Dispersal of individuals to nearby communities occurs whenever
their fitness falls below a predefined tolerance threshold. The spatiotemporal
dynamics of the model is described in terms of this threshold. We compare this
dynamics with the one obtained through density-independent dispersal and find
marked differences. In the community-driven scenario, the spatial correlations
in the population density do not vary in a linear fashion as we increase the
tolerance threshold. Instead we find the system to cross different dynamical
regimes as the threshold is raised. Spatial patterns evolve from disordered, to
scale-free complex patterns, to finally becoming well-organized domains. This
model therefore predicts that natural populations, the dispersal strategies of
which are likely to be influenced by their local environment, might be subject
to complex spatiotemporal dynamics.Comment: 43 pages, 7 figures, vocabulary modifications, discussion expanded,
references added, Ecological Complexity accepte
Moving forward in circles: challenges and opportunities in modelling population cycles
Population cycling is a widespread phenomenon, observed across a multitude of taxa in both laboratory and natural conditions. Historically, the theory associated with population cycles was tightly linked to pairwise consumer–resource interactions and studied via deterministic models, but current empirical and theoretical research reveals a much richer basis for ecological cycles. Stochasticity and seasonality can modulate or create cyclic behaviour in non-intuitive ways, the high-dimensionality in ecological systems can profoundly influence cycling, and so can demographic structure and eco-evolutionary dynamics. An inclusive theory for population cycles, ranging from ecosystem-level to demographic modelling, grounded in observational or experimental data, is therefore necessary to better understand observed cyclical patterns. In turn, by gaining better insight into the drivers of population cycles, we can begin to understand the causes of cycle gain and loss, how biodiversity interacts with population cycling, and how to effectively manage wildly fluctuating populations, all of which are growing domains of ecological research
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