Inbreeding depression in a rare deceptive orchid

2001 ◽  
Vol 79 (10) ◽  
pp. 1181-1188 ◽  
Author(s):  
Jean-Baptiste Ferdy ◽  
Sandrine Loriot ◽  
Michel Sandmeier ◽  
Madeleine Lefranc ◽  
Christian Raquin
Keyword(s):  
Inbreeding Depression ◽  
Conservation Biology ◽  
Resource Availability ◽  
Genetic Load ◽  
Outcrossing Rate ◽  
Deleterious Mutations ◽  
Geographic Scale ◽  
Deceptive Pollination ◽  
Inbreeding Level ◽  
Small Geographic Scale

We quantified inbreeding depression for seed maturation and germination in a deceptively pollinated orchid (Dactylorhiza praetermissa (Druce) Soó). Deceptive species do not provide any reward to their pollinators, which thus visit few flowers per plant. Therefore, deceptive species are predicted to experience high outcrossing. In agreement with the prediction that species with high outcrossing rate should possess a heavy genetic load, we demonstrated inbreeding depression in one of the populations we studied. More surprisingly, we found some evidence of inbreeding depression at a small geographic scale. This was not expected, as deceptive orchids generally disperse their pollen and their seeds over long distances. We also demonstrated that the position of a flower within an inflorescence interacts with the type of cross. This indicates that resource availability might modify how severely deleterious mutations affect reproductive success. This could also explain why the intensity of inbreeding depression seems, in the populations we studied, to be determined more by environmental factors than by inbreeding level, as estimated from molecular markers. Inferences in terms of conservation biology are drawn from these results.Key words: inbreeding depression, deceptive pollination, orchid, Dactylorhiza praetermissa.

scholarly journals Inbreeding depression due to mildly deleterious mutations in finite populations: size does matter

2000 ◽  
Vol 75 (1) ◽  
pp. 75-81 ◽  
Author(s):  
THOMAS BATAILLON ◽  
MARK KIRKPATRICK
Keyword(s):  
Population Size ◽  
Inbreeding Depression ◽  
Deleterious Mutation ◽  
Large Population ◽  
Genetic Load ◽  
Breeding Systems ◽  
Deleterious Mutations ◽  
Single Locus Analysis ◽  
Population Sizes ◽  
Inbreeding Rate

We studied the effects of population size on the inbreeding depression and genetic load caused by deleterious mutations at a single locus. Analysis shows how the inbreeding depression decreases as population size becomes smaller and/or the rate of inbreeding increases. This pattern contrasts with that for the load, which increases as population size becomes smaller but decreases as inbreeding rate goes up. The depression and load both approach asymptotic limits when the population size becomes very large or very small. Numerical results show that the transition between the small and the large population regimes is quite rapid, and occurs largely over a range of population sizes that vary by a factor of 10. The effects of drift on inbreeding depression may bias some estimates of the genomic rate of deleterious mutation. These effects could also be important in the evolution of breeding systems in hermaphroditic organisms and in the conservation of endangered populations.

scholarly journals Inbreeding depression and genetic load at partially linked loci in a metapopulation

2010 ◽  
Vol 92 (2) ◽  
pp. 127-140 ◽  
Author(s):  
SHU-RONG ZHOU ◽  
JOHN R. PANNELL
Keyword(s):  
Inbreeding Depression ◽  
Random Mating ◽  
Genetic Load ◽  
Minor Effect ◽  
Deleterious Mutations ◽  
Recombination Rates ◽  
Sexual Systems ◽  
Biological Phenomena ◽  
Population Turnover ◽  
Wide Range

SummaryInbreeding depression has important implications for a wide range of biological phenomena, such as inbreeding avoidance, the evolution and maintenance of sexual systems and extinction rates of small populations. Previous investigations have asked how inbreeding depression evolves in single and subdivided populations through the fixation of deleterious mutations as a result of drift, as well as through the expression of deleterious mutations segregating in a population. These studies have focused on the effects of mutation and selection at single loci, or at unlinked loci. Here, we used simulations to investigate the evolution of genetic load and inbreeding depression due to multiple partially linked loci in metapopulations. Our results indicate that the effect of linkage depends largely on the kinds of deleterious alleles involved. For weakly deleterious and partially recessive mutations, the speed of mutation accumulation at segregating loci in a random-mating subdivided population of a given structure tends to be retarded by increased recombination between adjacent loci – although the highest numbers of fixation of slightly recessive mutant alleles were for low but finite recombination rates. Although linkage had a relatively minor effect on the evolution of metapopulations unless very low values of recombination were assumed, close linkage between adjacent loci tended to enhance population structure and population turnover. Finally, within-deme inbreeding depression, between-deme inbreeding depression and heterosis generally increased with decreased recombination rates. Moreover, increased selfing reduced the effective amount of recombination, and hence the effects of tight linkage on metapopulation genetic structure were decreased with increasing selfing. In contrast, linkage had little effect on the fate of lethal and highly recessive alleles. We compare our simulation results with predictions made by models that ignore the complexities of recombination.

scholarly journals The Sheltered Genetic Load Linked to the S Locus in Plants: New Insights From Theoretical and Empirical Approaches in Sporophytic Self-Incompatibility

Genetics ◽  
2009 ◽  
Vol 183 (3) ◽  
pp. 1105-1118 ◽  
Author(s):  
Violaine Llaurens ◽  
Lucy Gonthier ◽  
Sylvain Billiard
Keyword(s):  
Inbreeding Depression ◽  
Balancing Selection ◽  
Genetic Load ◽  
Relative Fitness ◽  
Self Incompatibility ◽  
Deleterious Mutations ◽  
Gas Treatment ◽  
Genomic Inbreeding ◽  
Genomic Regions ◽  
Empirical Approaches

Inbreeding depression and mating systems evolution are closely linked, because the purging of deleterious mutations and the fitness of individuals may depend on outcrossing vs. selfing rates. Further, the accumulation of deleterious mutations may vary among genomic regions, especially for genes closely linked to loci under balancing selection. Sporophytic self-incompatibility (SSI) is a common genetic mechanism in angiosperm that enables hermaphrodite plants to avoid selfing and promote outcrossing. The SSI phenotype is determined by the S locus and may depend on dominance relationships among alleles. Since most individuals are heterozygous at the S locus and recombination is suppressed in the S-locus region, it has been suggested that deleterious mutations could accumulate at genes linked to the S locus, generating a “sheltered load.” In this article, we first theoretically investigate the conditions generating sheltered load in SSI. We show that deleterious mutations can accumulate in linkage with specific S alleles, and particularly if those S alleles are dominant. Second, we looked for the presence of sheltered load in Arabidopsis halleri using CO2 gas treatment to overcome self-incompatibility. By examining the segregation of S alleles and measuring the relative fitness of progeny, we found significant sheltered load associated with the most dominant S allele (S15) of three S alleles tested. This sheltered load seems to be expressed at several stages of the life cycle and to have a larger effect than genomic inbreeding depression.

scholarly journals The mutation load under tetrasomic inheritance and its consequences for the evolution of the selfing rate in autotetraploid species

1999 ◽  
Vol 74 (1) ◽  
pp. 31-42 ◽  
Author(s):  
J. RONFORT
Keyword(s):  
Inbreeding Depression ◽  
Deleterious Mutation ◽  
Stable State ◽  
Approximate Solutions ◽  
Balance Model ◽  
Deleterious Mutations ◽  
Selfing Rate ◽  
Mutation Load ◽  
Mean Fitness ◽  
The Mean

Single-locus equilibrium frequencies of a partially recessive deleterious mutation under the mutation–selection balance model are derived for partially selfing autotetraploid populations. Assuming multiplicative fitness interactions among loci, approximate solutions for the mean fitness and inbreeding depression values are also derived for the multiple locus case and compared with expectations for the diploid model. As in diploids, purging of deleterious mutations through consanguineous matings occurs in autotetraploid populations, i.e. the equilibrium mutation load is a decreasing function of the selfing rate. However, the variation of inbreeding depression with the selfing rate depends strongly on the dominance coefficients associated with the three heterozygous genotypes. Inbreeding depression can either increase or decrease with the selfing rate, and does not always vary monotonically. Expected issues for the evolution of the selfing rate consequently differ depending on the dominance coefficients. In some cases, expectations for the evolution of the selfing rate resemble expectations in diploids; but particular sets of dominance coefficients can be found that lead to either complete selfing or intermediate selfing rates as unique evolutionary stable state.

scholarly journals Inbred burying beetles suffer fitness costs from making poor decisions

2018 ◽  
Vol 285 (1881) ◽  
pp. 20180419 ◽  
Author(s):  
Jon Richardson ◽  
Pauline Comin ◽  
Per T. Smiseth
Keyword(s):  
Decision Making ◽  
Inbreeding Depression ◽  
Resource Availability ◽  
Environmental Conditions ◽  
Fitness Costs ◽  
Individual Decision ◽  
Burying Beetle ◽  
Individual Decision Making ◽  
Fitness Consequences ◽  
Nicrophorus Vespilloides

There is growing interest in how environmental conditions, such as resource availability, can modify the severity of inbreeding depression. However, little is known about whether inbreeding depression is also associated with differences in individual decision-making. For example, decisions about how many offspring to produce are often based upon the prevailing environmental conditions, such as resource availability, and getting these decisions wrong may have important fitness consequences for both parents and offspring. We tested for effects of inbreeding on individual decision-making in the burying beetle Nicrophorus vespilloides, which uses the size of a carrion resource to make decisions about number of offspring. Both inbred and outbred females adjusted their initial decisions about number of eggs to lay based on carcass size. However, when we forced individuals to update this initial decision by providing them with a different-sized carcass partway through reproduction, inbred females failed to update their decision about how many larvae to cull. Consequently, inbred females reared too many larvae, resulting in negative fitness consequences in the form of smaller offspring and reduced female post-reproductive condition. Our study provides novel insights into the effects of inbreeding by showing that poor decision-making by inbred individuals can negatively affect fitness.

scholarly journals Lethals in subdivided populations

2005 ◽  
Vol 86 (1) ◽  
pp. 41-51 ◽  
Author(s):  
SYLVAIN GLÉMIN
Keyword(s):  
Population Structure ◽  
Population Size ◽  
Inbreeding Depression ◽  
Deleterious Mutations ◽  
Mutation Load ◽  
General Picture ◽  
Analytical Approximations ◽  
Size Population ◽  
Subdivided Populations ◽  
Numerical Approaches

The fate of lethal alleles in populations is of interest in evolutionary and conservation biology for several reasons. For instance, lethals may contribute substantially to inbreeding depression. The frequency of lethal alleles depends on population size, but it is not clear how it is affected by population structure. By analysing the case of the infinite island model by numerical approaches and analytical approximations it is shown that, like population size, population structure affects the fate of lethal alleles if dominance levels are low. Inbreeding depression caused by such alleles is also affected by the population structure, whereas the mutation load is only weakly affected. Heterosis also depends on population structure, but it always remains low, of the order of the mutation rate or less. These patterns are compared with those caused by mildly deleterious mutations to give a general picture of the effect of population structure on inbreeding depression, heterosis, and the mutation load.

scholarly journals Associative overdominance caused by linked detrimental mutations

1971 ◽  
Vol 18 (3) ◽  
pp. 277-286 ◽  
Author(s):  
Tomoko Ohta
Keyword(s):  
Blood Group ◽  
Inbreeding Depression ◽  
Recombination Fraction ◽  
Abo Blood Group ◽  
Deleterious Mutations ◽  
Method Of Moment ◽  
Moment Equations ◽  
Neutral Locus ◽  
Neutral Marker ◽  
Image Position

SUMMARYAssociative overdominance due to linked detrimental mutations was investigated using the method of moment equations based on diffusion models. The expectation of the apparent selective value at the marker (neutral) locus has been evaluated. Assume two linked loci, at one of which the steady flux equilibrium is reached under constant mutational input of deleterious mutations (with rate v) having disadvantages hs in heterozygote and s in homozygotes. At another locus, the neutral alleles are segregating with frequencies near 0·5. Let Ne be the effective size of the population and c be the recombination fraction between the two loci. Then the coefficient of associative overdominance at the neutral locus can be obtained by taking the expectation with respect to chromosome frequencies at steady flux equilibrium. It becomes approximatelywhere (LI−L0) is the inbreeding depression caused by deleterious mutations under complete inbreeding, and Nehs ≫ l and hs ≫ v are assumed. More generally, if the inbreeding depression of a chromosome segment with a length of recombination fraction C is (LI−L0) then s′ at the neutral marker at the edge of the segment iswhere hs is the average heterozygote disadvantage of detrimentals.The significance of the associative overdominance is discussed in relation to actual observations. It is proposed that the most of the observed heterozygote superiority including inversion chromosomes of Drosophila, isozyme alleles in Avena and ABO blood group genes in man could be explained by the associated detrimentals.

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