Offspring are likely to be in an environment with parasites that have adapted to be able to attack their parents, so producing offspring that are genetically variable and not identical to either parent may result in offspring having higher resistance to parasites, and therefore better survival. Now that we have seen hypotheses that can explain how sex can evolve within a species, let's see what effects it has once it does evolve. One thing sexual reproduction may do is to affect the rate of speciation. Since sexual reproduction causes recombination of genes, it produces new combinations of alleles at different genes much more quickly than does asexual reproduction. Based on this increase in genetic variability in sexual species, evolution can occur more rapidly, so speciation should also occur more rapidly.
Sexual reproduction is thus subject to species selection.
As with other cases of species selection, note that this does not explain why sexual reproduction evolves within a species. It may, however, help to explain why there are so many more sexual species than there are asexual species.