The Role of Genes of Large Effect on Inbreeding Depression in Mimulus guttatus

Evolution ◽  
1999 ◽  
Vol 53 (6) ◽  
pp. 1678 ◽  
Author(s):  
John H. Willis
Keyword(s):  
Inbreeding Depression ◽  
Mimulus Guttatus

scholarly journals Evidence for the partial dominance of viability genes contributing to inbreeding depression in Mimulus guttatus.

Genetics ◽  
1994 ◽  
Vol 136 (1) ◽  
pp. 323-331
Author(s):  
Y B Fu ◽  
K Ritland
Keyword(s):  
Inbreeding Depression ◽  
Wild Plant ◽  
Mimulus Guttatus ◽  
Selfed Progeny ◽  
Partial Dominance ◽  
Complete Dominance ◽  
Model Free ◽  
Segregation Ratios ◽  
Marker Loci ◽  
In The Wild

Abstract The relative importance of different modes of gene expression of viability genes contributing to inbreeding depression was investigated in the wild plant, Mimulus guttatus. Viability genes were identified by self-fertilizing 31 outbred plants, each heterozygous for three to nine unlinked allozyme markers, and analyzing segregation ratios of selfed progeny at maturity for deviations from 1:2:1 ratios. In this study, 24 linkages of viability genes to marker loci were detected. To infer the nature of gene action for these viability genes, a "model-free" graphical method was developed that examines the "space" of segregation ratios allowed by each of seven selection models (i.e., overdominance, complete recessivity, partial recessivity, additivity, partial dominance, complete dominance and underdominance). Using this method, we found that, of 24 linkages detected, 18 were consistent with either partial dominance, complete dominance or underdominance. Six were consistent with either partial recessivity, complete recessivity or overdominance. This finding indicates that, in these chromosomal segments identified by allozyme markers, partial dominance plays the predominant role in inbreeding depression. This is inconsistent with either the dominance or overdominance hypotheses proposed to account for inbreeding depression.

scholarly journals Maternal effects alter the severity of inbreeding depression in the offspring

2016 ◽  
Vol 283 (1838) ◽  
pp. 20161023 ◽  
Author(s):  
Natalie Pilakouta ◽  
Per T. Smiseth
Keyword(s):  
Maternal Effects ◽  
Inbreeding Depression ◽  
Potential Role ◽  
Causal Effect ◽  
Natural Populations ◽  
Larval Survival ◽  
Burying Beetle ◽  
Nicrophorus Vespilloides ◽  
Selection For

A maternal effect is a causal influence of the maternal phenotype on the offspring phenotype over and above any direct effects of genes. There is abundant evidence that maternal effects can have a major impact on offspring fitness. Yet, no previous study has investigated the potential role of maternal effects in influencing the severity of inbreeding depression in the offspring. Inbreeding depression is a reduction in the fitness of inbred offspring relative to outbred offspring. Here, we tested whether maternal effects due to body size alter the magnitude of inbreeding depression in the burying beetle Nicrophorus vespilloides . We found that inbreeding depression in larval survival was more severe for offspring of large females than offspring of small females. This might be due to differences in how small and large females invest in an inbred brood because of their different prospects for future breeding opportunities. To our knowledge, this is the first evidence for a causal effect of the maternal phenotype on the severity of inbreeding depression in the offspring. In natural populations that are subject to inbreeding, maternal effects may drive variation in inbreeding depression and therefore contribute to variation in the strength and direction of selection for inbreeding avoidance.

Marker-based inferences about fecundity genes contributing to inbreeding depression in Mimulus guttatus

Genome ◽  
1994 ◽  
Vol 37 (6) ◽  
pp. 1005-1010 ◽  
Author(s):  
Yong-Bi Fu ◽  
Kermit Ritland
Keyword(s):  
Genetic Markers ◽  
Inbreeding Depression ◽  
Phenotypic Variation ◽  
Mimulus Guttatus ◽  
Selfed Progeny ◽  
Partial Dominance ◽  
Number Of Genes ◽  
Isozyme Loci ◽  
Deleterious Genes

Eight unlinked isozyme loci were used as genetic markers to characterize fecundity genes contributing to inbreeding depression in two selfed progeny arrays of Mimulus guttatus. Five fecundity traits were measured. Six of eight marked chromosomal segments were significantly associated with the expression of these traits. The number of genes detected for five traits in two progeny arrays varied, with an average of 2.8 genes per trait. Individual segments explained 1.44–9.29%, and together accounted for 3.85–11.32%, of phenotypic variation. Of 20 significant associations, 10 could be interpreted as exhibiting partial dominance, 7 overdominance, 3 partial recessivity, and 0 underdominance. Significant pairwise epistasis was rare. The results of this study suggest that inbreeding depression is caused by many deleterious genes of relatively small, partially dominant effects.Key words: linkage, isozymes, QTLs, inbreeding depression, Mimulus guttatus.

scholarly journals Point estimation and graphical inference of marginal dominance for two viability loci controlling inbreeding depression

1997 ◽  
Vol 70 (2) ◽  
pp. 143-153 ◽  
Author(s):  
YONG-BI FU ◽  
DEBORAH CHARLESWORTH ◽  
GENE NAMKOONG
Keyword(s):  
Inbreeding Depression ◽  
Gene Action ◽  
Marker Locus ◽  
Point Estimation ◽  
Relative Role ◽  
Selfed Progeny ◽  
Deterministic Analysis ◽  
Partial Dominance ◽  
Segregation Ratios

A deterministic analysis is conducted to examine marginal dominance for two linked viability loci influencing inbreeding depression and its graphical inferences. Four estimators of marginal dominance are derived, assuming a biallelic marker locus completely linked to one of the viability loci, and the biases in expected estimates due to the other deleterious locus are discussed. Three conditions under which apparent partial dominance or underdominance could occur are found, i.e. when two multiplicative, partially recessive loci are linked in coupling phase and when two synergistic, highly overdominant loci are linked in coupling or repulsion phases. Expected frequencies of the three marker genotypes in selfed progeny are derived, considering two linkage phases, two types of marker locus position with respect to the viability loci, and the multiplicative and synergistic fitness models. Segregation ratios are generated for the marker locus linked to either two overdominant or partially recessive loci and plotted in gene action graphs to examine the robustness of the graphical inferences of gene action due to the presence of an additional linked viability locus. Under a multiplicative fitness model, the presence of an additional partially recessive or overdominant locus in the vicinity of the marker locus does not greatly affect the graphical inferences of the relative role of partially recessive or overdominant genes in expression of inbreeding depression. A marker linked to two synergistic, highly overdominant loci can behave as though linked to a partially recessive, partially dominant or underdominant locus, even with relatively weak synergism.

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