SPECIATIONS AND EXTINCTIONS IN A SELF-ORGANIZING CRITICAL MODEL OF TREE-LIKE EVOLUTION

We study analytically a simple model of a self-organized critical evol ution. The model considers both extinction and speciation events leadi ng to the growth of phylogenetic-like trees. Through a mean-field like theory, we study the evolution of the local configurations for the tr ee leaves. The fitness threshold, below which life activity takes plac e through avalanches of all sizes is calculated. The transition betwee n speciating (evolving) and dead trees is obtained and is in agreement with numerical simulations. Moreover, this theoretical work suggests that the structure of the tree is strongly dependent on the extinction strength.