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

2002 ◽  
Vol 80 (2) ◽  
pp. 107-116 ◽  
Author(s):  
KONSTANTINOS THEODOROU ◽  
DENIS COUVET
Keyword(s):  
Gene Flow ◽  
Mating System ◽  
Inbreeding Depression ◽  
Genetic Load ◽  
Negative Influence ◽  
Point Of View ◽  
Mixed Mating ◽  
Isolated Populations ◽  
Seed Migration ◽  
Subdivided Population

We investigate the joint effects of gene flow and selfing on the level of inbreeding depression, heterosis and genetic load in a subdivided population at equilibrium. Low gene flow reduces inbreeding depression and substantially increases heterosis. However, in highly self-fertilizing populations, inbreeding depression is independent of the amount of gene flow. When migration occurs via pollen, consanguinity of the reproductive system could have a negative influence on subpopulation persistence, in contrast to the case of isolated populations. However, with only seed migration, genetic load and heterosis depend mildly on the mating system. From an evolutionary point of view, we reach two main conclusions: first, outcrossing is selected for if gene flow is low; second, intermediate levels of gene flow could promote mixed mating systems, especially when migration occurs through pollen.

scholarly journals The mixed mating system of the sea palm kelp Postelsia palmaeformis : few costs to selfing

2010 ◽  
Vol 278 (1710) ◽  
pp. 1347-1355 ◽  
Author(s):  
Allison K. Barner ◽  
Catherine A. Pfister ◽  
J. Timothy Wootton
Keyword(s):  
Mating System ◽  
First Generation ◽  
Genetic Load ◽  
Mixed Mating ◽  
Reproductive Assurance ◽  
Isolated Populations ◽  
Mixed Mating System ◽  
Fitness Consequences ◽  
Limited Dispersal ◽  
Self Fertilization

Naturally isolated populations have conflicting selection pressures for successful reproduction and inbreeding avoidance. These species with limited seasonal reproductive opportunities may use selfing as a means of reproductive assurance. We quantified the frequency of selfing and the fitness consequences for inbred versus outcrossed progeny of an annual kelp, the sea palm ( Postelsia palmaeformis ). Using experimentally established populations and microsatellite markers to assess the extent of selfing in progeny from six founding parents, we found the frequency of selfing was higher than expected in every population, and few fitness costs were detected in selfed offspring. Despite a decline in heterozygosity of 30 per cent in the first generation of selfing, self-fertilization did not affect individual size or reproduction, and correlated only with a marginally significant decline in survival. Our results suggest both that purging of deleterious recessive alleles may have already occurred and that selfing may be key to reproductive assurance in this species with limited dispersal. Postelsia has an alteration of a free-living diploid and haploid stage, where the haploid stage may provide increased efficiency for purging the genetic load. This life history is shared by many seaweeds and may thus be an important component of mating system evolution in the sea.

scholarly journals How much gene flow is needed to avoid inbreeding depression in wild tiger populations?

2014 ◽  
Vol 281 (1789) ◽  
pp. 20133337 ◽  
Author(s):  
John Kenney ◽  
Fred W. Allendorf ◽  
Charles McDougal ◽  
James L. D. Smith
Keyword(s):  
Gene Flow ◽  
Inbreeding Depression ◽  
Negative Impact ◽  
Genetic Load ◽  
Habitat Connectivity ◽  
Medium Size ◽  
Infrastructure Development ◽  
Population Isolation ◽  
Source Populations ◽  
Seven Generations

The number and size of tiger populations continue to decline owing to habitat loss, habitat fragmentation and poaching of tigers and their prey. As a result, tiger populations have become small and highly structured. Current populations have been isolated since the early 1970s or for approximately seven generations. The objective of this study is to explore how inbreeding may be affecting the persistence of remaining tiger populations and how dispersal, either natural or artificial, may reduce the potentially detrimental effect of inbreeding depression. We developed a tiger simulation model and used published levels of genetic load in mammals to simulate inbreeding depression. Following a 50 year period of population isolation, we introduced one to four dispersing male tigers per generation to explore how gene flow from nearby populations may reduce the negative impact of inbreeding depression. For the smallest populations, even four dispersing male tigers per generation did not increase population viability, and the likelihood of extinction is more than 90% within 30 years. Unless habitat connectivity is restored or animals are artificially introduced in the next 70 years, medium size wild populations are also likely to go extinct, with only four to five of the largest wild tiger populations likely to remain extant in this same period without intervention. To reduce the risk of local extinction, habitat connectivity must be pursued concurrently with efforts to increase population size (e.g. enhance habitat quality, increase habitat availability). It is critical that infrastructure development, dam construction and other similar projects are planned appropriately so that they do not erode the extent or quality of habitat for these populations so that they can truly serve as future source populations.

scholarly journals Life cycle expression of inbreeding depression in Eucalyptus regnans and inter-generational stability of its mixed mating system

2019 ◽  
Vol 124 (1) ◽  
pp. 179-187 ◽  
Author(s):  
A Rod Griffin ◽  
Brad M Potts ◽  
René E Vaillancourt ◽  
J Charles Bell
Keyword(s):  
Life Cycle ◽  
Mating System ◽  
Inbreeding Depression ◽  
Field Experiments ◽  
Natural Populations ◽  
Forest Tree ◽  
Mixed Mating ◽  
Mature Trees ◽  
Mixed Mating System ◽  
Eucalyptus Regnans

Abstract Background and Aims Many plants exhibit a mixed mating system. Published models suggest that this might be an evolutionarily stable rather than a transitional state despite the presence of inbreeding depression, but there is little empirical evidence. Through field experimentation, we studied the role of inbreeding depression in eliminating inbred progeny from the reproductive cohort of the forest tree Eucalyptus regnans, and demonstrate a stable mixed primary mating system over two successive generations. Methods Two field experiments were conducted using seed from natural populations. We sowed open-pollinated seeds to simulate a natural regeneration event and determined isozyme genotypes of dominant and suppressed individuals over 10 years. We also planted a mixture of open-pollinated, outcross and selfed families with common maternal parentage; monitored survival of cross types over 29 years; and determined the percentage of outcrosses in open-pollinated seed from a sample of reproductively mature trees using microsatellite analysis. Key Results Both experiments demonstrated progressive competitive elimination of inbred plants. By 29 years, the reproductive cohort in the planted experiment consisted only of outcrosses which produced seed which averaged 66 % outcrosses, similar to the estimate for the parental natural population (74 %). Conclusions Selective elimination of inbred genotypes during the intense intra-specific competition characteristic of the pre-reproductive phase of the life cycle of E. regnans results in a fully outcrossed reproductive population, in which self-fertility is comparable with that of its parental generation. The mixed mating system may be viewed as an unavoidable consequence of the species’ reproductive ecology, which includes the demonstrated effects of inbreeding depression, rather than a strategy which is actively favoured by natural selection.

Mating system of Calluna vulgaris: self-sterility and outcrossing estimations

1998 ◽  
Vol 76 (1) ◽  
pp. 37-42 ◽  
Author(s):  
Grégory Mahy ◽  
Anne-Laure Jacquemart
Keyword(s):  
Mating System ◽  
Inbreeding Depression ◽  
Calluna Vulgaris ◽  
Pollen Tubes ◽  
Outcrossing Rate ◽  
Evolutionary Significance ◽  
Mixed Mating ◽  
Mixed Mating System ◽  
Cross Pollination ◽  
Mating System Evolution

The evolutionary significance of a mixed mating system is currently under debate. Calluna vulgaris (L). Hull, a widespread European shrub, is likely to undergo mixed mating because of geitonogamy. Mating system was investigated in three populations of C. vulgaris by means of greenhouse controlled crosses, pollen tube observations, and outcrossing rate estimations from allozyme markers. The species is highly self-sterile, most probably as a result of early inbreeding depression. Mean fruit set and mean seed number per fruit following hand self-pollination were 48 and 13%, respectively, of those following cross-pollination. Pollen tubes produced by self pollen penetrated the ovary with the same success as those from cross-pollination. Multilocus estimates of the outcrossing rates ranged from 0.71 to 0.90, and two estimates were significantly different from 1.00. Calluna vulgaris could thus be classified as being mixed mating with predominant allogamy. Single-locus estimates did not differ significantly from multilocus estimates suggesting that biparental inbreeding did not contribute to the apparent selfing rate. The maintenance of high early inbreeding depression despite an intermediate level of selfing is discussed with respect to recent theories on mating system evolution. Key words: Calluna vulgaris, mating system, self-sterility, pollen tubes, outcrossing rate, inbreeding depression.

scholarly journals Outbreeding and possibly inbreeding depression in a pollinating fig wasp with a mixed mating system

Heredity ◽  
2009 ◽  
Vol 102 (4) ◽  
pp. 349-356 ◽  
Author(s):  
J M Greeff ◽  
G J Jansen van Vuuren ◽  
P Kryger ◽  
J C Moore
Keyword(s):  
Mating System ◽  
Inbreeding Depression ◽  
Mixed Mating ◽  
Fig Wasp ◽  
Mixed Mating System

scholarly journals Comparative effects of pollen and seed migration on the cytonuclear structure of plant populations. II. Paternal cytoplasmic inheritance.

Genetics ◽  
1992 ◽  
Vol 132 (1) ◽  
pp. 253-267
Author(s):  
A Schnabel ◽  
M A Asmussen
Keyword(s):  
Gene Flow ◽  
De Novo ◽  
Life Stage ◽  
Cytoplasmic Inheritance ◽  
Island Population ◽  
Mixed Mating ◽  
Plant Populations ◽  
Seed Migration ◽  
Self Fertilization ◽  
The Relationship

Abstract We continue our study of the effects of pollen and seed migration on the cytonuclear structure of mixed-mating plant populations by analyzing two deterministic continent-island models under the critical assumption of paternal cytoplasmic inheritance. The major results of this study that contrast with our previous conclusions based on maternal cytoplasmic inheritance are (i) pollen gene flow can significantly affect the cytonuclear structure of the island population, and in particular can help to generate cytonuclear disequilibria that greatly exceed the magnitude of those that would be produced by seed migration or mixed mating alone; (ii) with simultaneous pollen and seed migration, nonzero cytonuclear disequilibria will be maintained not only when there is disequilibrium in the immigrant pollen or seeds, but also through a variety of intermigrant admixture effects when the two pools of immigrants differ appropriately in their cytonuclear compositions; (iii) either immigrant pollen or immigrant seeds can generate disequilibria de novo in populations with initially random cytonuclear associations, but pollen migration alone generally produces lower levels of disequilibrium than does comparable seed migration, especially at high levels of self-fertilization when the overall fraction of immigrant pollen is low; (iv) the equilibrium state of the island population will be influenced by the rate of pollen gene flow whenever there is either allelic disequilibrium in the immigrant pollen or simultaneous seed migration coupled with different cytoplasmic or nuclear allele frequencies in immigrant pollen and seeds or nonzero allelic disequilibrium in either immigrant pool. The estimation of pollen migration should therefore be facilitated with paternal cytoplasmic inheritance relative to the case of maternal cytoplasmic inheritance. These basic conclusions hold whether the population is censused as seeds or as adults, but with simultaneous pollen and seed migration, the relationship between census time and the ability to detect nonrandom cytonuclear associations is complex. When migration is through pollen alone, however, the cytonuclear structure of the island population is independent of the life stage censused.

scholarly journals Gene flow and mating system of the tropical tree Sextonia rubra

2005 ◽  
Vol 54 (1-6) ◽  
pp. 275-280 ◽  
Author(s):  
V. Veron ◽  
H. Caron ◽  
B. Degen
Keyword(s):  
Gene Flow ◽  
Mating System ◽  
Tree Species ◽  
Pollen Dispersal ◽  
Joint Estimation ◽  
Tropical Tree ◽  
Effective Density ◽  
Mixed Mating ◽  
Tropical Tree Species ◽  
High Level

Abstract In this paper we report a study of the mating system and gene flow of Sextonia rubra, a hermaphroditic, insect pollinated tropical tree species with a geographic distribution in the Guyana Plateau and the Amazon. Using five microsatellites we analysed 428 seeds of 27 open pollinated families at the experimental site “Paracou” in French Guiana. We observed, compared to other tropical tree species, a high level of genetic diversity. We estimated parameters of the mating system and gene flow by using the mixed mating model and the TwoGener approach. The estimated multilocus outcrossing rate, tm, was 0.992 indicating nearly complete outcrossing. A significant level of biparental inbreeding and a small proportion of full-sibs were estimated for the 27 seed arrays. The differentiation of allelic frequencies among the pollen pools was ΦFT = 0.061. We estimated mean pollen dispersal distances between 65 m and 89 m according to the dispersal models used. The joint estimation of pollen dispersal and density of reproductive trees gave an effective density estimate of 2.1-2.2 trees/ha.

scholarly journals The Effects of Pollen and Seed Migration on Nuclear-Dicytoplasmic Systems. II. A New Method for Estimating Plant Gene Flow From Joint Nuclear-Cytoplasmic Data

Genetics ◽  
2000 ◽  
Vol 155 (2) ◽  
pp. 833-854 ◽  
Author(s):  
Maria E Orive ◽  
Marjorie A Asmussen
Keyword(s):  
Gene Flow ◽  
Simulated Data ◽  
Likelihood Method ◽  
Data Sets ◽  
Mixed Mating ◽  
Hybrid Zones ◽  
Plant Gene ◽  
Seed Migration ◽  
Genotype Frequencies ◽  
Source Populations

Abstract A new maximum-likelihood method is developed for estimating unidirectional pollen and seed flow in mixed-mating plant populations from counts of joint nuclear-cytoplasmic genotypes. Data may include multiple unlinked nuclear markers with a single maternally or paternally inherited cytoplasmic marker, or with two cytoplasmic markers inherited through opposite parents, as in many conifer species. Migration rate estimates are based on fitting the equilibrium genotype frequencies under continent-island models of plant gene flow to the data. Detailed analysis of their equilibrium structures indicates when each of the three nuclear-cytoplasmic systems allows gene flow estimation and shows that, in general, it is easier to estimate seed than pollen migration. Three-locus nuclear-dicytoplasmic data only increase the conditions allowing seed migration estimates; however, the additional dicytonuclear disequilibria allow more accurate estimates of both forms of gene flow. Estimates and their confidence limits for simulated data sets confirm that two-locus data with paternal cytoplasmic inheritance provide better estimates than those with maternal inheritance, while three-locus dicytonuclear data with three modes of inheritance generally provide the most reliable estimates for both types of gene flow. Similar results are obtained for hybrid zones receiving pollen and seed flow from two source populations. An estimation program is available upon request.

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