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C. FERREIRA In A. Abraham, J. Ruiz-del-Solar, and M. Köppen (eds), Soft Computing Systems: Design, Management and Applications, pp. 153-162, IOS Press, Netherlands, 2002.

Analyzing the Founder Effect in Simulated Evolutionary Processes Using Gene Expression Programming

Artificial Evolutionary Systems and the Founder Effect
The question of the initial diversity is pertinent in artificial evolutionary systems for two main reasons. First, the random generation of viable individuals in some complex problems can be a rare event and, in those cases, it would be advantageous if the evolutionary process could get started from one or a few founder individuals; whether this is possible or not, will depend on the modification mechanisms available to the system. And, second, because of this, the kind of mechanism used to create genetic variation becomes of paramount importance. If genetic variation is created by non-homogenizing operators such as point mutation, then populations will be able to adapt and evolve. However, if genetic variation is created by homogenizing operators (recombination), then evolution is either altogether halted when only one founder individual is available or seriously compromised when the number of founder individuals is excessively small.

The importance of the initial diversity in evolution was stressed by E. Mayr in what he called founder effect speciation [10, 11]. This process may be thought of as the establishment of a new population due to a founder event initiated by genetic drift and followed by natural selection. An extreme case of a founder event is the colonization of a previously uninhabited area by a single pregnant female. In nature, besides recombination, other genetic operators are used to create modification and populations that pass through a bottleneck are capable of adaptation, sometimes even originating new species.

Similarly, in artificial evolutionary systems, the capability of founder populations to evolve depends greatly on the kind of mechanism used to create genetic modification. Indeed, if homogenizing operators are the only source of genetic modification, populations will either be unable to evolve efficiently or not at all in the extreme case of only one founder individual.

In this work, different populations of computer programs will be used to analyze the founder effect in evolution. One kind of population uses point mutation as the only source of genetic modification and the other uses only recombination.

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