Ezequiel A. Di Paolo
A simple computational model of parapatric speciation is introduced and analysed within the framework of the Dobzhansky-Muller model of accumulations of incompatible mutations. It is shown that speciation can occur without the need of physical barriers in environments showing non-uniform local conditions. A population of ancestor agents is placed in an artificial environment, their fitnesses depending on the balance of energy intakes and costs caused by movement and heat dissipation during their lifetime. Phenotypic features such as thermal resistivity are encoded genetically and the agents are able to interbreed locally. It is observed that the accumulation of mutations cause the formation of neighbouring populations showing localized adaptation but still able to interbreed with the ancestor populations. It is argued that this is a case of polytypic species or ``subspecies''. However this does not necessarily happen between populations separated by one or more subspecies, and speciation can be said to occur in this case, which can be viewed as the emergence of allopatricity without any previous physical barriers.
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