Explaining the selective forces that underlie different reproductive modes forms a major part of evolution research. Many organisms are facultative sexuals, with the ability to reproduce both sexually and asexually. Reduced sequencing costs means it is now possible to start investigating genome sequences of a wider number of these organisms in depth, but teasing apart the genetic forces underlying the maintenance of facultative sexual reproduction remains a challenge. An analogous problem exists when determining the genetic consequences of a degree of outcrossing (and recombination) in otherwise self-fertilising organisms. Here, I provide an overview of existing research on the basis behind the evolution of different reproductive modes, with a focus on explaining the population-genetic effects favouring low outcrossing rates in either partially selfing or asexual species. I review the outcomes that both self-fertilisation and asexuality have on either purging deleterious mutations or fixing beneficial alleles, and what empirical data exists to support these theories. In particular, a greater application of mathematical models to genomic data has provided insight into the numerous effects that the transitions to self-fertilisation from outcrossing have on genetic architecture. Similar modelling approaches could be used to determine the forces shaping genetic diversity of facultative sexual species. Hence a further unification of mathematical models with next-generation sequence data will prove important in exploring the genetic influences on reproductive system evolution. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.