The evolution and breakdown of S-allele systems

Charlesworth, Deborah; Charlesworth, Brian

doi:10.1038/hdy.1979.58

Cited by 131 publications

(138 citation statements)

References 49 publications

Supporting

Mentioning

127

Contrasting

Order By: Relevance

“…This corresponds to a frequency of the self-compatible genotype of 0014, and the frequency of heterozygotes for the self-compatibility allele was 0277. Such populations therefore have intermediate selfing rates, as previously found also by Charlesworth and Charlesworth (1979b) for the case of gametophytic action, when self-compatibility alleles are introduced into the population. This situation is different from other models that yield intermediate selfing rates as their evolutionary outcome (reviewed in Charlesworth and Charlesworth, 1987), in that it arises from the nature of the genetic control of the compatibility versus incompatibility.…”

Section: Discussionsupporting

confidence: 55%

“…This is what one would expect to find if the different alleles evolved from an ancestral inactive allele, assuming that the only alleles likely to invade the population would be ones with new S specificities not already present (Charlesworth and Charlesworth, 1979b); thus new alleles arising by mutation would be unlikely to spread if they occurred in alleles that were already active in the population, but an allele derived from S by changing a different amino acid site from those present in existing alleles could invade, provided that it produced a protein with an S specificity. Different alleles produced in this way would therefore differ by at least two amino acids from one another.…”

Section: Discussionmentioning

confidence: 71%

“…Sporophytic self-incompatibility systems have now been discovered in four more families (Convolvulaceae: Martin, 1968;Kowyama et a!., 1980, Betulaceae: Thompson, 1979Germain eta!., 1981;Me and Radicati, 1983, Caryophyllaceae: Lundkvist, 1979, Sterculiaceae: Jacob, 1980. So far, most attempts to think about the evolution of homomorphic self-incompatibility have either been vague about what type of system is being considered (Whitehouse, 1950; 1952, p. 291), or have explicitly considered the gametophytic type of system (Charlesworth and Charlesworth, 1979b). …”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Evolution of homomorphic sporophytic self-incompatibility

Charlesworth

1988

Heredity

Self Cite

View full text Add to dashboard Cite

A population genetic model is described for the evolution of sporophytic self-incompatibility by successive mutations to active incompatibility alleles from an ancestral compatibility, Sf, allele, homozygotes for which are capable of selffertilisation. For spread of the active incompatibility alleles there must be strong inbreeding depression. It is shown that polymorphism for the ancestral allele and the active alleles is generated, unless the number of active alleles becomes very large. Thus, although there is selection for alleles that cause outcrossing, such polymorphic populations would not be completely outcrossing, but would have selfing rates between zero and the selfling rate of the homozygote for S1. The equilibrium frequencies of the active alleles depend on whether dominance or independent action is assumed for the alleles in the pistil. In either case the equilibrium allele frequencies are higher than would be the case for gametophytically acting alleles.

show abstract

Section: Discussionsupporting

confidence: 55%

Section: Discussionmentioning

confidence: 71%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Evolution of homomorphic sporophytic self-incompatibility

Charlesworth

1988

Heredity

Self Cite

View full text Add to dashboard Cite

show abstract

“…Classical theory dictates that an allele conferring SC should either be able to spread to fixation, if inbreeding depression can be purged, or should be rapidly lost, if not (eg, Charlesworth and Charlesworth, 1979;Lande and Schemske, 1985). Recent theory suggests, in contrast, that SI and SC alleles may stably coexist under certain conditions (Uyenoyama et al, 2001;Porcher and Lande, 2005).…”

Section: Breakdown Of Si Permits Short-term Allelic Diversificationmentioning

confidence: 99%

Rapid recent radiation of S-RNase lineages in Witheringia solanacea (Solanaceae)

Stone

Pierce

2005

Heredity

View full text Add to dashboard Cite

Strong frequency-dependent selection as found in the selfincompatibility loci of flowering plants maintains allelic lineages for extremely long time scales, such that allelic genealogies can shed insight into long-term demographic patterns of species. Effective mutation rate, as well as demographic change such as population bottlenecks, can influence genealogical structure. In addition, loss of functionality at the self-incompatibility locus is likely to affect radiation rates. Partial sequences for 21 S-RNase alleles of the mid-elevation tropical species Witheringia solanacea were obtained in order to compare their substitution rates and genealogy with those of Witheringia maculata and two species in the closely related genus Physalis. Sequences for W. solanacea fell into the three clades within the Solanaceae already identified for the genus. Terminal branch lengths for W. solanacea, scaled to the total depth of its phylogeny, were intermediate between the unusually short terminal branches of W. maculata and those of the two Physalis species. In contrast to the Physalis species, where interspecific d N /d S for closely related alleles exceeded 1.0 to the same degree as did intraspecific d N /d S , in Witheringia only intraspecific comparisons showed an excess of nonsynonymous substitutions, suggesting postspeciation radiation of alleles. Alleles associated with lowered S-RNase production and self-compatibility showed extremely short terminal branches. In summary, it appears that rapid recent diversification of alleles characterizes the Witheringia lineages. In some cases, this rapid diversification can be attributed to relaxed constraints due to breakdown of selfincompatibility. Heredity (2005) 94, 547-555.

show abstract

“…Inbreeding depression decreases as population size becomes smaller due to reduced polymorphism for selection to act on (Bataillon and Kirkpatrick, 2000). Charlesworth and Charlesworth (1979) showed that the number of S-alleles also is important in maintaining SI, because a low number of alleles will limit the number of compatible crosses in the population. A decrease in population size can also cause a reduction in the number of S-alleles (Brennan et al, 2003), and a self-compatible mutant can be positively selected for (Reinartz and Les, 1994).…”

Section: Introductionmentioning

confidence: 99%

Genetic diversity and fitness in small populations of partially asexual, self-incompatible plants

2009

View full text Add to dashboard Cite

How self-incompatibility systems are maintained in plant populations is still a debated issue. Theoretical models predict that self-incompatibility systems break down according to the intensity of inbreeding depression and number of S-alleles. Other studies have explored the function of asexual reproduction in the maintenance of self-incompatibility. However, the population genetics of partially asexual, self-incompatible populations are poorly understood and previous studies have failed to consider all possible effects of asexual reproduction or could only speculate on those effects. In this study, we investigated how partial asexuality may affect genetic diversity at the S-locus and fitness in small self-incompatible populations. A genetic model including an S-locus and a viability locus was developed to perform forward simulations of the evolution of populations of various sizes. Drift combined with partial asexuality produced a decrease in the number of alleles at the S-locus. In addition, an excess of heterozygotes was present in the population, causing an increase in mutation load. This heterozygote excess was enhanced by the self-incompatibility system in small populations. In addition, in highly asexual populations, individuals produced asexually had some fitness advantages over individuals produced sexually, because sexual reproduction produces homozygotes of the deleterious allele, contrary to asexual reproduction. Our results suggest that future research on the function of asexuality for the maintenance of self-incompatibility will need to (1) account for whole-genome fitness (mutation load generated by asexuality, self-incompatibility and drift) and (2) acknowledge that the maintenance of self-incompatibility may not be independent of the maintenance of sex itself.

show abstract

The evolution and breakdown of S-allele systems

Cited by 131 publications

References 49 publications

Evolution of homomorphic sporophytic self-incompatibility

Evolution of homomorphic sporophytic self-incompatibility

Rapid recent radiation of S-RNase lineages in Witheringia solanacea (Solanaceae)

Genetic diversity and fitness in small populations of partially asexual, self-incompatible plants

Contact Info

Product

Resources

About