Inbreeding depression and heterosis in a subdivided population: influence of the mating system

Theodorou, Konstantinos; Couvet, Denis

doi:10.1017/s0016672302005785

Cited by 48 publications

(44 citation statements)

References 37 publications

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“…In this study we used recently diverged experimental populations to which we applied self-pollination, within-and between-population crosses to investigate the link between the genetic structure of the subdivided population, and fitness-related traits values in the firstgeneration offspring, by assessing within-population heterosis or inbreeding depression, between-population heterosis or genetic load and outbreeding depression. This approach is complementary and intermediate to analytical and simulation studies (Theodorou and Couvet, 2002;Glemin et al, 2003;Jaquiéry et al, 2009) and experimental crosses in natural populations (Fenster and Galloway, 2000;Newman and Tallmon, 2001; because much information on the history of the populations (time since divergence, population census sizes, initial diversity and so on) is available. We found high and significant inbreeding depression within populations for four of six traits with systematic superiority of within-population cross progeny compared with selfed progeny.…”

Section: Discussionmentioning

confidence: 99%

Inbreeding depression and low between-population heterosis in recently diverged experimental populations of a selfing species

et al. 2010

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In fragmented populations, genetic drift and selection reduce genetic diversity, which in turn results in a loss of fitness or in a loss of evolvability. Genetic rescue, that is, controlled input of diversity from distant populations, may restore evolutionary potential, whereas outbreeding depression might counteract the positive effect of this strategy. We carried out self-pollination and crosses within and between populations in an experimental subdivided population of a selfing species, Triticum aestivum L., to estimate the magnitude of these two phenomena. Surprisingly, for a self-fertilizing species, we found significant inbreeding depression within each population for four of the six traits studied, indicating that mildly deleterious mutations were still segregating in these populations. The progeny of within-and betweenpopulation crosses was very similar, indicating low betweenpopulation heterosis and little outbreeding depression. We conclude that relatively large population effective sizes prevented fixation of a high genetic load and that local adaptation was limited in these recently diverged populations. The kinship coefficient estimated between the parents using 20 neutral markers was a poor predictor of the progeny phenotypic values, indicating that there was a weak link between neutral diversity and genes controlling fitnessrelated traits. These results show that when assessing the viability of natural populations and the need for genetic rescue, the use of neutral markers should be complemented with information about the presence of local adaptation in the subdivided population.

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Section: Discussionmentioning

confidence: 99%

Inbreeding depression and low between-population heterosis in recently diverged experimental populations of a selfing species

et al. 2010

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“…Both of these measures will not be influenced by strongly deleterious alleles, which are held at mutation-selection balance in all populations. Although the latter approach provides no information on the degree of dominance, this definition focuses on the increase in fitness within populations caused by hybridization (Whitlock et al 2000;Theodorou and Couvet 2002;Roze and Rousset 2004). In this study, heterosis equals:…”

Section: Heterosismentioning

confidence: 99%

“…In small populations, a large number of these slightly deleterious mutations may actually become fixed by genetic drift. As the effective size of a population declines, a greater fraction of the segregating genetic load within a population is fixed by drift, being converted into a ''local drift load'' that may significantly reduce fitness (Lande 1994;Lynch et al 1995a;Wang et al 1999;Bataillon and Kirkpatrick 2000;Whitlock et al 2000;Theodorou and Couvet 2002;Glémin 2003;Glé-min et al 2003;Roze and Rousset 2004). It has been proposed that mildly deleterious mutations may even endanger the persistence of extremely small populations if they reduce fitness to the point where reproduction no longer replaces parents, such that a ''mutational meltdown'' occurs (Lynch and Gabriel 1990;Lynch et al 1995a;Saccheri et al 1998).…”

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confidence: 99%

“…In contrast, strong isolation should cause populations to lose fitness, as these mutations drift to high frequency (Whitlock et al 2000). Under realistic scenarios for mutation rates to deleterious alleles, the effects of these alleles on fitness, and rates of migration, theory suggests that fitness losses within finite populations could range from as low as 5% to as high as 60% (Crow 1948;Whitlock et al 2000;Theodorou and Couvet 2002;Glémin et al 2003;Roze and Rousset 2004). Crosses between small and/or isolated populations indeed often suggest a substantial local drift load, based on evidence that interpopulation hybrids show heterosis for fitness caused by elevated heterozygosity at many loci (Crow 1948;Levin 1984;van Treuren et al 1993;Hauser and Loeschcke 1994;Ouborg and van Treuren 1994;Heschel and Paige 1995;Richards 2000;Paland and Schmid 2003).…”

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confidence: 99%

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Heterosis in an Isolated, Effectively Small, and Self-Fertilizing Population of the Flowering Plant Leavenworthia Alabamica

Busch

2006

Evolution

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Abstract. Mildly deleterious mutations are thought to play a major role in the extinction of natural populations, especially those that are small, isolated, or inbred. Self-fertilization should reduce the effective size of populations and simultaneously reduce migration between populations. A history of self-fertilization should therefore cause a population to harbor a substantial ''local drift load'' caused by the fixation of mildly deleterious mutations. This hypothesis was tested in Leavenworthia alabamica, which contains large, self-incompatible populations and smaller self-compatible populations with adaptations for self-fertilization. The fitness of offspring from within-and between-population crosses was compared to quantify heterosis caused by the masking of deleterious alleles in the heterozygous state. Little heterosis was observed in crosses between five large, self-incompatible populations and two of the three small, self-fertilizing populations of L. alabamica. However, the most geographically isolated and genetically divergent self-fertilizing population (Tuscumbia) exhibited a 110.2% increase in germination and a 73.6% increase in fitness, which is consistent with a sizeable local drift load. The finding of substantial heterosis for fitness supports the idea that small effective size, reproductive isolation, and self-fertilization can make populations particularly vulnerable to mutation accumulation.

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“…Proposals included using heterosis generated by migration to reinforce populations, i.e., a form of genetic rescue (Richards 2000;Willi and Fischer 2005;Hogg et al 2006;Willi et al 2007), or to understand the success of hybrid invaders (Facon et al 2005). Heterosis may also play a role in the evolution of life-history traits, such as dispersal (Guillaume and Perrin 2006;Roze and Rousset 2009) or outcrossing (Ronfort and Couvet 1995;Theodorou and Couvet 2002).…”

Section: Rosses Between Individuals From Different Pop-mentioning

confidence: 99%

Surprising Fitness Consequences of GC-Biased Gene Conversion. II. Heterosis

Glémin

2011

Genetics

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Heterosis is a widespread phenomenon corresponding to the increase in fitness following crosses between individuals from different populations or lines relative to their parents. Its genetic basis has been a topic of controversy since the early 20th century. The masking of recessive deleterious mutations in hybrids likely explains a substantial part of heterosis. The dynamics and consequences of these mutations have thus been studied in depth. Recently, it was suggested that GC-biased gene conversion (gBGC) might strongly affect the fate of deleterious mutations and may have significant fitness consequences. gBGC is a recombination-associated process mimicking selection in favor of G and C alleles, which can interfere with selection, for instance by increasing the frequency of GC deleterious mutations. I investigated how gBGC could affect the amount and genetic structure of heterosis through an analysis of the interaction between gBGC and selection in subdivided populations. To do so, I analyzed the infinite island model both by numerical computations and by analytical approximations. I showed that gBGC might have little impact on the total amount of heterosis but could greatly affect its genetic basis.

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Inbreeding depression and heterosis in a subdivided population: influence of the mating system

Cited by 48 publications

References 37 publications

Inbreeding depression and low between-population heterosis in recently diverged experimental populations of a selfing species

Inbreeding depression and low between-population heterosis in recently diverged experimental populations of a selfing species

Heterosis in an Isolated, Effectively Small, and Self-Fertilizing Population of the Flowering Plant Leavenworthia Alabamica

Surprising Fitness Consequences of GC-Biased Gene Conversion. II. Heterosis

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