Evolutionary suicide
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ABSTRACT The great majority of species that lived on this earth have gone extinct. These extinctions are often explained by invoking changes in the environment, to which the species has been unable to adapt. Evolutionary suicide is an alternative explanation to such extinctions. It is an evolutionary process in which a viable population adapts in such a way that it can no longer persist. In this paper different models, where evolutionary suicide occurs are discussed, and the theory behind the phenomenon is reviewed.
1. INTRODUCTION Modern evolutionary theory has been widely used to understand phenotypic evolution because of natural selection. One interesting phenomenon is evolutionary branching (Metz et al., 1996a; Geritz et al., 1997, 1998), where strategies first approach monomorphically a singular strategy, but then divide into two groups, and evolve further away from each other. The question whether evolutionary branching can lead to sympatric speciation, has raised a lot of interest (Dieckmann and Doebeli, 1999; Dieckmann et al., 2004). The enormous number of different living species gives motivation for such studies. However, an even larger number of species are known to have gone extinct. These extinctions are often explained by invoking changes in the environment, to which the species has been unable to adapt. This paper concentrates on another possible explanation, which is a kind of reverse evolutionary branching. In some occasions, the species in question could persist with its current strategy, but natural selection forces the species to change its strategy resulting in extinction. This phenomenon is called evolutionary suicide (Ferri`ere, 2000), but it is also called Darwinian extinction (Webb, 2003), and evolution to extinction (Dieckmann et al., 1995). The word evolution suggests itself that it would act for the good of the population. For this reason, evolutionary suicide may seem counterintuitive. However, evolution operates at the level of individuals. Those individuals who get most offspring in the current environment will increase in frequency. As a result, the environment experienced by the individuals will change. This change is not necessarily a good one for the population. Already Darwin (1859, 1871) observed that natural selection may favour traits that eventually, through a feedback to the environment, turn out to be harmful to the individuals. The peacock’s tail is a typical example of this. This topic was later discussed in detail by Haldane (1932). Evolutionary suicide is an extreme example of such a harmful event. In Section 2 the modelling framework used in this paper is presented, including the framework of adaptive dynamics (Metz et al., 1992, 1996a; Dieckmann and Law, 1996; Acta Biotheoretica (2005) 53: 241–264
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Springer 2005
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K. PARVINEN
Geritz et al., 1997, 1998). After that, a mathematical definition of different types of evolutionary suicide will be given, together with some simple examples. In Section 3 the theory behind evolutionary suicide will be studied. It is
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