Sporadic sexual reproduction: Sex to some degree

Beukeboom, Leo W.

doi:10.1038/sj.hdy.6800926

Cited by 7 publications

(2 citation statements)

References 6 publications

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“…Apomictic plants still produce the same reproductive organs as sexuals, including insect-attracting flowers and functional pollen (for example, Meirmans et al ., 2006; Van Dijk, 2007). Similar patterns are observed in sporadically asexual animals, such as flatworms ( Schmidtea polychroa ): reproduction is occasionally asexual but still sperm dependent and depending on the main organs for sexual reproduction (Beukeboom, 2007). That is, the shift from apomixis back to sexuality confers usually only a low cost because most features and organs related to sexuality have been retained.…”

Section: A Combinational Theory For the Evolution Of Sex In Eukaryotessupporting

confidence: 54%

A combinational theory for maintenance of sex

Hörandl

2009

Heredity

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Sexual reproduction implies high costs, but it is difficult to give evidence for evolutionary advantages that would explain the predominance of meiotic sex in eukaryotes. A combinational theory discussing evolution, maintenance and loss of sex may resolve the problem. The main function of sex is the restoration of DNA and consequently a higher quality of offspring. Recombination at meiosis evolved, perhaps, as a repair mechanism of DNA strand damages. This mechanism is most efficient for DNA restoration in multicellular eukaryotes, because the initial cell starts with a re-optimized genome, which is passed to all the daughter cells. Meiosis acts also as creator of variation in haploid stages, in which selection can purge most efficiently deleterious mutations. A prolonged diploid phase buffers the effects of deleterious recessive alleles as well as epigenetic defects and is thus optimal for prolonged growth periods. For complex multicellular organisms, the main advantage of sexuality is thus the alternation of diploid and haploid stages, combining advantages of both. A loss of sex is constrained by several, partly group-specific, developmental features. Hybridization may trigger shifts from sexual to asexual reproduction, but crossing barriers of the parental sexual species limit this process. For the concerted break-up of meiosis-outcrossing cycles plus silencing of secondary features, various group-specific changes in the regulatory system may be required. An establishment of asexuals requires special functional modifications and environmental opportunities. Costs for maintenance of meiotic sex are consequently lower than a shift to asexual reproduction.

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Section: A Combinational Theory For the Evolution Of Sex In Eukaryotessupporting

confidence: 54%

A combinational theory for maintenance of sex

Hörandl

2009

Heredity

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“…However, release of male genetic material into the egg cytoplasm does not necessarily equate to sexual recombination since any sperm material can be expelled from the egg. Sperm dependent parthenogenesis, for example, is displayed by the hermaphrodite flatworm Schmidtea polychroa [42]. Further evidence of genetic exchange in the evolutionary history of gyrodactylids through sexual reproduction comes from previous phylogenetic studies (e.g.…”

Section: Discussionmentioning

confidence: 99%

Mixed Infections and Hybridisation in Monogenean Parasites

et al. 2012

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Theory predicts that sexual reproduction promotes disease invasion by increasing the evolutionary potential of the parasite, whereas asexual reproduction tends to enhance establishment success and population growth rate. Gyrodactylid monogeneans are ubiquitous ectoparasites of teleost fish, and the evolutionary success of the specious Gyrodactylus genus is thought to be partly due to their use of various modes of reproduction. Gyrodactylus turnbulli is a natural parasite of the guppy (Poecilia reticulata), a small, tropical fish used as a model for behavioural, ecological and evolutionary studies. Using experimental infections and a recently developed microsatellite marker, we conclusively show that monogenean parasites reproduce sexually. Conservatively, we estimate that sexual recombination occurs and that between 3.7–10.9% of the parasites in our experimental crosses are hybrid genotypes with ancestors from different laboratory strains of G. turnbulli. We also provide evidence of hybrid vigour and/or inter-strain competition, which appeared to lead to a higher maximum parasite load in mixed infections. Finally, we demonstrate inbreeding avoidance for the first time in platyhelminths which may influence the distribution of parasites within a host and their subsequent exposure to the host's localized immune response. Combined reproductive modes and inbreeding avoidance may explain the extreme evolutionary diversification success of parasites such as Gyrodactylus, where host-parasite coevolution is punctuated by relatively frequent host switching.

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Sperm-Dependent Parthenogenesis and Hybridogenesis in Teleost Fishes

2009

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In so-called unisexual teleost fishes, a broad spectrum of evolutionary stages with varying amounts of sexual elements has evolved. These range from pure sperm-dependent parthenogenesis (gynogenesis) without or with different amounts of paternal leakage to hybridogenesis with hemiclonal diploid gametogenesis or genome elimination followed by meiosis (meiotic hybridogenesis). All of these phenomena are of hybrid origin. Many of these fish form complexes which involve the coexistence of one or more sexually reproducing species with derived all-female forms that have various ploidy levels and reproductive modes, including gynogenesis, (meiotic) hybridogenesis and sexual reproduction. In teleosts, parthenogenetic reproduction is strictly dependent on sperm to initiate embryonic development. As opposed to true parthenogenesis, sperm-dependent parthenogenetic teleost lineages must primarily coexist with their "sperm donor", usually males from a parental sexual lineage or from a related sexual species. In some systems, gynogens were able to escape from their initial sperm donors ("host switch") and therefore, to enlarge their ranges and ecological niches. Sperm donors normally do not contribute genetically to the next generation. However, paternal leakage is observed in many systems contributing differing amounts of genetic material (from microchromosomes to entire chromosome sets) allowing interaction between genomes of different origin. Hybridogenesis is similar to gynogenesis in depending upon coexistence with sexual species but incorporates recombined genetic material by true fertilization. While hybridogens usually form clonal gametes, some triploids are capable of genome elimination followed by a normal diploid meiosis. Sperm-dependent parthenogenesis and hybridogenesis

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Sporadic sexual reproduction: Sex to some degree

Cited by 7 publications

References 6 publications

A combinational theory for maintenance of sex

A combinational theory for maintenance of sex

Mixed Infections and Hybridisation in Monogenean Parasites

Sperm-Dependent Parthenogenesis and Hybridogenesis in Teleost Fishes

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