RNA viruses are known to replicate with extremely high mutation rates. These rates are actually close to the so-called error threshold. This threshold is in fact a critical point beyond which genetic information is lost through a second-order phase transition, which has been dubbed the ``error...

Models of habitat fragmentation have mainly explored the effects on a few species ecologies or on a hierarchical community of competitors. These models reveal that, under different conditions, ecosystem response can underly sharp changes when some given thresholds are reached. Here we explore...

Zipf's law states that the frequency of a word is a power function of its rank. The exponent of the power is usually accepted to be close to (-)1. Great deviations between the predicted and real number of different words of a text, disagreements between the predicted and real exponent of the...

One of the most popular data sets in ecology, that of lynx fur returns, is analyzed in order to look for evidence for a bifurcation process. This bifurcation seems to be present from the observation of a shift in the amplitude of oscillations of the lynx time series. The possibility for such a...

A dynamical model of an ecological community is analyzed within a "mean-field approximation" in which one of the species interacts with the combination of all of the other species in the community. Within this approximation the model may be formulated as a master equation describing a one-step...

In a recent study, Ohira and Sawatari presented a simple model of computer network traffic dynamics. These authors showed that a phase transition point is present separating the low-traffic phase with no congestion from the congestion phase as the packet creation rate increases. We further...

A new model ecosystem consisting of many interacting species is introduced. The species are connected through a random matrix with a given connectivity . It is shown that the system is organized close to a boundary of marginal stability in such a way that fluctuations follow power law...

Many complex systems can be described in terms of networks of interacting units. Recent studies have shown that a wide class of both natural and artificial nets display a surprisingly widespread feature: the presence of highly heterogeneous distributions of links, providing an extraordinary...

The topology of the proteome map revealed by recent large-scale hybridization methods has shown that the distribution of protein-protein interactions is highly heterogeneous, with many proteins having few links while a few of them are heavily connected. This particular topology is shared by...

Extinction has been seldom considered as a relevant ingredient of neodarwinian theories. The fact, however, is that the number of species extinctions in the history of life is almost the same as the number of originations. The fossil record indicates that extinction events are patterned in some...