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Currently, the understanding of evolution patterns of genomes on different phylogenetic groups is a hot topic in evolutionary biology.The arrival of next generation sequencing (NGS) technologies and the generation of huge amounts of genomic data is allowing researchers to dig in the past and better resolve organisms’ natural history as well as evolutionary enigmas.Sexuality is a crucial factor molding the genomic features of eukaryotes. doi: 10.1086/523369 Cross Ref Full Text | Google Scholar © 2015 Hojsgaard and Hörandl.In plants, the formation of a new individual through sexuality involves an alternation between the sporophytic (2n) and the gametophytic (n) generations via meiosis and gamete fusion, the two mechanisms that create new genetic combinations. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY).One of such enigmas is the predominance of sex in nature (Otto, 2009).One of the most prominent theories explaining the benefits of sex (for broad analyses see, e.g., Bell, 1982; Birdsell and Wills, 2003) proposes that sexuality protects the genome from the accumulation of deleterious mutations (Muller, 1964; Kondrashov, 1988; Hörandl, 2009; Figure 1). (A) Scheme of distributions (p) of mutations in a sexual population.
Sexuality has the effect that deleterious mutations appear in various genotypic configurations in the offspring. We discuss a general model that the observed incidence of facultative sexuality in plants may unmask deleterious mutations with partial dominance and expose them efficiently to purging selection.A little bit of sex may help to avoid genomic decay and extinction.The genetic load of clonal lineages will reduce their fitness and obstruct further adaptation, driving those lineages to an early extinction (Maynard Smith, 1978; Bell, 1982). Model of purging mutations in a tetraploid, facultative apomictic plant lineage (blue column) compared to an obligate apomict (without meiosis; green column). For simplicity, the model is presented for a new self-fertile allotetraploid lineage with regularly reduced male gametes; and partial dominant mutations are considered to be deleterious and expressed a 50% penetrance. doi: 10.1111/j.1469-8137.2006.01738.x Pubmed Abstract | Pubmed Full Text | Cross Ref Full Text | Google Scholar Paun, O., Greilhuber, J., Temsch, E., and Hörandl, E. Patterns, sources and ecological implications of clonal diversity in apomictic Ranunculus carpaticola (Ranunculus auricomus) complex, Ranunculaceae.
In apomictic plants, a combination of complex developmental features avoid recombination and reductional steps present in the normal sexual reproductive process, thus developing a seed carrying a clonal embryo (Asker and Jerling, 1992).