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Outcrossing
About: Outcrossing is a research topic. Over the lifetime, 2837 publications have been published within this topic receiving 112488 citations.
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TL;DR: An analysis of twelve plant families indicated that species within families with predominately outcrossing, woody species had more genetic diversity and less interpopulation differentiation than species withinfamilies with predominate herbaceous species.
Abstract: Seven two-trait combinations (e.g. breeding system and seed dispersal mechanism) of five life history characteristics were used to analyse interspecific variation in the level and distribution of allozyme genetic diversity in seed plants. Highly significant differences were seen among categories for all seven comparisons. Life form and breeding system had highly significant influences on genetic diversity and its distribution. Regardless of other traits, outcrossing species tended to be more genetically diverse and had less genetic differentiation among their populations. Similarly, woody plants have less among population differentiation and somewhat more genetic diversity than non-woody species with similar life history traits. An analysis of twelve plant families indicated that species within families with predominately outcrossing, woody species had more genetic diversity and less interpopulation differentiation than species within families with predominately herbaceous species.
2,090 citations
TL;DR: In this article, a compilation of 307 studies using nuclear DNA markers for evaluating among-and within-population diversity in wild angiosperms and gymnosperms was made, which indicated that long-lived, outcrossing, late successional taxa retain most of their genetic variability within populations.
Abstract: A compilation was made of 307 studies using nuclear DNA markers for evaluating among- and within-population diversity in wild angiosperms and gymnosperms. Estimates derived by the dominantly inherited markers (RAPD, AFLP, ISSR) are very similar and may be directly comparable. STMS analysis yields almost three times higher values for within-population diversity whereas among-population diversity estimates are similar to those derived by the dominantly inherited markers. Number of sampled plants per population and number of scored microsatellite DNA alleles are correlated with some of the population genetics parameters. In addition, maximum geographical distance between sampled populations has a strong positive effect on among-population diversity. As previously verified with allozyme data, RAPD- and STMS-based analyses show that long-lived, outcrossing, late successional taxa retain most of their genetic variability within populations. By contrast, annual, selfing and/or early successional taxa allocate most of the genetic variability among populations. Estimates for among- and within-population diversity, respectively, were negatively correlated. The only major discrepancy between allozymes and STMS on the one hand, and RAPD on the other hand, concerns geographical range; within-population diversity was strongly affected when the former methods were used but not so in the RAPD-based studies. Direct comparisons between the different methods, when applied to the same plant material, indicate large similarities between the dominant markers and somewhat lower similarity with the STMS-based data, presumably due to insufficient number of analysed microsatellite DNA loci in many studies.
1,718 citations
TL;DR: The genetic basis of inbreeding depression and of the related phenomenon, heterosis, has been a puzzle for many decades as mentioned in this paper, based on recent studies in many species, the authors argue that both phenomena are predominantly caused by the presence of recessive deleterious mutations in populations.
Abstract: The genetic basis of inbreeding depression and of the related phenomenon, heterosis, has been a puzzle for many decades. Based on recent studies in many species, the authors argue that both phenomena are predominantly caused by the presence of recessive deleterious mutations in populations. Inbreeding depression — the reduced survival and fertility of offspring of related individuals — occurs in wild animal and plant populations as well as in humans, indicating that genetic variation in fitness traits exists in natural populations. Inbreeding depression is important in the evolution of outcrossing mating systems and, because intercrossing inbred strains improves yield (heterosis), which is important in crop breeding, the genetic basis of these effects has been debated since the early twentieth century. Classical genetic studies and modern molecular evolutionary approaches now suggest that inbreeding depression and heterosis are predominantly caused by the presence of recessive deleterious mutations in populations.
1,604 citations
TL;DR: Genetic models are constructed which allow inbreeding depression to change with the mean selfing rate in a population by incorporating both mutation to recessive and partially dominant lethal and sublethal alleles at many loci and mutation in quantitative characters under stabilizing selection.
Abstract: The amounts of inbreeding depression upon selfing and of heterosis upon outcrossing determine the strength of selection on the selfing rate in a population when this evolves polygenically by small steps. Genetic models are constructed which allow inbreeding depression to change with the mean selfing rate in a population by incorporating both mutation to recessive and partially dominant lethal and sublethal alleles at many loci and mutation in quantitative characters under stabilizing selection. The models help to explain observations of high inbreeding depression (> 50%) upon selfing in primarily outcrossing populations, as well as considerable heterosis upon outcrossing in primarily selfing populations. Predominant selfing and predominant outcrossing are found to be alternative stable states of the mating system in most plant populations. Which of these stable states a species approaches depends on the history of its population structure and the magnitude of effect of genes influencing the selfing rate.
1,601 citations
TL;DR: Woody species with large geographic ranges, outcrossing breeding systems, and wind or animal-ingested seed dispersal have more genetic diversity within species and populations but less variation among populations than woodyspecies with other combinations of traits.
Abstract: The plant allozyme literature was reviewed to: (1) compare genetic diversity in long-lived woody species with species representing other life forms, and (2) to investigate whether the levels and distribution of genetic diversity in woody species are related to life history and ecological characteristics. Data from 322 woody taxa were used to measure genetic diversity within species, and within and among populations of species. Woody species maintain more variation within species and within populations than species with other life forms but have less variation among populations. Woody species with large geographic ranges, outcrossing breeding systems, and wind or animal-ingested seed dispersal have more genetic diversity within species and populations but less variation among populations than woody species with other combinations of traits. Although life history and ecological traits explain a significant proportion (34%) of the variation among species for the genetic parameters measured, a large proportion of the interspecific variation is unexplained. The specific evolutionary history of each species must play an important role in determining the level and distribution of genetic diversity.
1,515 citations