Using Microevolution to Explain the Macroevolutionary Observations for the Evolution of Sex

Abstract

Macroevolution deals with large-scale and complex changes such as the rise of species, mass extinctions, and evolutionary trends. Microevolution describes evolutionary change within a species with changes in allele or genotype frequencies over short time periods. The separation of the two processes is somewhat arbitrary however, as macroevolution is the accumulation of a number of microevolutionary changes leading over time to large-scale changes. As a consequence, understanding macroevolution requires understanding microevolutionary processes. In this chapter we discuss this link between macro- and micro-evolution using the example of the evolution of sexual reproduction. Explaining the evolution of sexual reproduction is one of the most puzzling problems in evolutionary biology and despite ongoing research a general explanation for the evolution and maintenance of sex has not yet been widely confirmed. Sexual reproduction has been suggested to have evolved only once from asexual reproduction during the early stages of the eukaryote evolution. Today, we find that almost all animals and plants reproduce sexually rather than asexually, suggesting that sex is advantageous. There are, however, exemptions from the macroevolutionary observation of the ubiquity of sexual reproduction: asexual taxa are found across almost the whole phylogenetic tree in a twig-like pattern, and these asexual taxa are found in habitats where related sexual taxa are often absent. The evolution of sex, with all its superlatives such as ‘the queen of evolutionary problems’ and the ‘evolutionary scandals’ of the ancient asexuals, is probably one of the fields in evolutionary biology, where already early on macroevolutionary patterns were directly related to microevolutionary processes. Examples of the literature are reviewed here with an emphasis on the link between macro- and microevolution.