Blackwell Publishing

Adaptations in sexual reproduction - Why do organisms reproduce sexually?


Is this a group selectionist account of the advantage of sexual reproduction, or not?

To say that sexual populations have a lower extinction rate than asexual populations is to say one thing: to say that sex exists because of its lower extinction rate is to say something much stronger.

It could be that sex exists in sexual species because sex is advantageous to the individuals of those species, and asexual reproduction exists in asexual species because it is advantageous to the individuals in those species. The different extinction rates would then be species-level consequences of different individual adaptations in the two types of species. By analogy, carnivores could have higher extinction rates than herbivores, but that would not mean that herbivory was disadvantageous to individual herbivores and maintained because of its advantage to the group.

The taxonomic distribution of asexuality, therefore, although it is consistent with the group selectionist theory of sex, does not confirm it. The same pattern could have arisen if sex had an individual advantage.

Figure: the taxonomic distribution of asexual reproduction is spindly; it is found in odd, isolated taxa.

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