Populations of species in ecosystems are constrained by the availability of resources within their environment. In effect this means that a growth of one population, needs to be balanced by the reduction in size of others. In neutral models of biodiversity all populations are assumed to change incrementally due to stochastic births and deaths of individuals. Here we propose and model another redistribution mechanism driven by abrupt  collapses of the entire population of a single species freeing up resources for the remaining ones. This mechanism may be relevant  for communities of bacteria, with strain-specific collapses caused e.g. by invading bacteriophages, or for other ecosystems where infectious diseases play an important role. The emergent property of the population dynamics in our system are cyclic "diversity waves" triggered by collapses of globally dominating populations. The population diversity in the environment peaks at the beginning of each wave and exponentially decreases afterwards. Population sizes in our system follow a bimodal distribution with the lower peak composed of the recently collapsed or the newly arrived species. In contrast to this, the upper peak of the distribution consists of the surviving species in the current diversity wave. The populations of the most abundant species in the upper peak exhibit a scale-free  distribution with a nearly universal exponent of about 1.7. We show that our model is robust with respect to variations in dynamical rules including gradual redistribution of populations between subsequent collapses and variation in species' growth or collapse rates .
Populations of species in ecosystems are often constrained by availability of resources within their environment. In effect this means that a growth of one population, needs to be balanced by comparable reduction in populations of others. In neutral models of biodiversity all populations are assumed to change incrementally due to stochastic births and deaths of individuals. Here we propose and model another redistribution mechanism driven by abrupt and severe collapses of the entire population of a single species freeing up resources for the remaining ones. This mechanism may be relevant e.g. for communities of bacteria, with strain-specific collapses caused e.g. by invading bacteriophages, or for other ecosystems where infectious diseases play an important role. The emergent dynamics of our system is cyclic "diversity waves" triggered by collapses of globally dominating populations. The population diversity peaks at the beginning of each wave and exponentially decreases afterwards. Species abundances are characterized by a bimodal time-aggregated distribution with the lower peak formed by populations of recently collapsed or newly introduced species, while the upper peak - species that has not yet collapsed in the current wave. In most waves both upper and lower peaks are composed of several smaller peaks. This URLanized hierarchical peak structure has a long-term memory transmitted across several waves. It gives rise to a scale-free tail of the time-aggregated population distribution with a universal exponent of 1.7. We show that diversity wave dynamics is robust with respect to variations in the rules of our model such as diffusion between multiple environments, species-specific growth and extinction rates, and bet-hedging strategies .
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constrained by the
often constrained by
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the reduction in size
comparable reduction in populations
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and severe
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e.g.
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property of the population dynamics in our system are
dynamics of our system is
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in the environment
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Population sizes in our system follow a bimodal
Species abundances are characterized by a bimodal time-aggregated
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composed of the
formed by populations of
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the newly arrived species. In contrast to this,
newly introduced species, while
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of the distribution consists of the surviving species
- species that has not yet collapsed
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diversity wave. The populations of the most abundant species in the upper peak exhibit a
wave. In most waves both upper and lower peaks are composed of several smaller peaks. This URLanized hierarchical peak structure has a long-term memory transmitted across several waves. It gives rise to a
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tail of the time-aggregated population
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nearly
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about
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our model
diversity wave dynamics
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dynamical rules including gradual redistribution of populations between subsequent collapses and variation in species' growth or collapse rates
the rules of our model such as diffusion between multiple environments, species-specific growth and extinction rates, and bet-hedging strategies