The nematode Caenorhabditis elegans reproduces primarily by self-fertilization of hermaphrodites, yet males are present at low frequencies in natural populations (androdioecy). The ancestral state of C. elegans was probably gonochorism (separate males and females), as in its relative C. remanei. Males may be maintained in C. elegans because outcrossed individuals escape inbreeding depression. T...

Both the spatial distribution of organisms and their mode of reproduction have important effects on the change in allele frequencies within populations. In this article, we study the combined effect of population structure and the rate of partial selfing of organisms on the efficiency of selection against recurrent deleterious mutations. Assuming an island model of population structure and weak...

Cytological analysis of microsporogenesis in 72 popcorn plants, comprising nine from the original population (CMS-43, S(0)) and 63 from seven cycles of self-fertilization (S(1) to S(7)), one plant of S(0) generation (plant 2) was identified with B chromosomes. The number of B chromosomes varied from two to three in the same anther. The pattern of chromosome pairing and meiotic behavior of Bs we...

The common transition from out-crossing to self-fertilization in plants decreases effective population size. This is expected to result in a reduced efficacy of natural selection and in increased rates of protein evolution in selfing plants compared with their outcrossing congeners. Prior analyses, based on a very limited number of genes, detected no differences between the rates of protein evo...

BACKGROUND AND AIMS Flowering plants display considerable variation in mating system, specifically the relative frequency of cross- and self-fertilization. The majority of estimates of outcrossing rate do not account for temporal variation, particularly during the flowering season. Here, we investigated seasonal variation in mating and fertility in Incarvillea sinensis (Bignoniaceae), an annual...

Self-incompatibility (SI) is a genetic system found in some hermaphrodite plants. Recognition of pollen by pistils expressing cognate specificities at two linked genes leads to rejection of self pollen and pollen from close relatives, i.e., to avoidance of self-fertilization and inbred matings, and thus increased outcrossing. These genes generally have many alleles, yet the conditions allowing ...

Recombination is a powerful policing mechanism to control intragenomic cheats. The "parliament of the genes" can often rapidly block driving genes from cheating during meiosis. But what if the genome parliament is reduced to only two members, or supergenes? Using a series of simple game-theoretic models inspired by the peculiar genetics of Oenothera sp., we illustrate that a two supergene genom...

BACKGROUND AND AIMS The frequency at which males can be maintained with hermaphrodites in androdioecious populations is predicted to depend on the selfing rate, because self-fertilization by hermaphrodites reduces prospective siring opportunities for males. In particular, high selfing rates by hermaphrodites are expected to exclude males from a population. Here, the first estimates are provided...

It has been suggested that clonality provides reproductive assurance in cross-fertilizing species subject to pollen limitation, relieving one of the main selective pressures favoring the evolution of self-fertilization. According to this hypothesis, cross-fertilizing species subject to pollen limitation should often be clonal. Here, we investigated the association between clonality and a geneti...

Floral morphology determines the pattern of pollen transfer within and between individuals. In hermaphroditic species, the spatial arrangement of sexual organs influences the rate of self-pollination as well as the placement of pollen in different areas of the pollinator's body. Studying the evolutionary modification of floral morphology in closely related species offers an opportunity to inves...