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Network Models of Phage-Bacteria Coevolution
Bacteria and their bacteriophages are the most abundant, widespread and
diverse groups of biological entities on the planet. In an attempt to
understand how the interactions between bacteria, virulent phages and temperate
phages might affect the diversity of these groups, we developed a novel
stochastic network model for examining the co-evolution of these ecologies. In
our approach, nodes represent whole species or strains of bacteria or phages,
rather than individuals, with "speciation" and extinction modelled by
duplication and removal of nodes. Phage-bacteria links represent host-parasite
relationships and temperate-virulent phage links denote prophage-encoded
resistance. The effect of horizontal transfer of genetic information between
strains was also included in the dynamical rules. The observed networks evolved
in a highly dynamic fashion but the ecosystems were prone to collapse (one or
more entire groups going extinct). Diversity could be stably maintained in the
model only if the probability of speciation was independent of the diversity.
Such an effect could be achieved in real ecosystems if the speciation rate is
primarily set by the availability of ecological niches.Comment: 8 pages, 6 figure
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