Inbreeding and Outbreeding

1947 ◽  
Vol 1947 (01) ◽  
pp. 7-27 ◽  
Author(s):  
Forbes W. Robertson
Keyword(s):  
Mating System ◽  
Mating Systems ◽  
Careful Consideration ◽  
Population Variance ◽  
Rule Of Thumb ◽  
Cell Divisions ◽  
Particulate Nature ◽  
Genetic Complexity ◽  
Environmental Variations ◽  
Successive Generations

The type of mating system we should use in any plan of livestock improvement requires very careful consideration. By reason of the particulate nature of inheritance and the behaviour of chromosomes in the cell divisions preceding the formation of eggs and sperm, the various mating systems differ in their influence upon the uniformity or otherwise of successive generations, the chances of securing improvement, the scope for control by selection, and finally, our ability to discriminate between the relative contributions of genetic and environmental variations to the population variance. Because of the genetic complexity many misconceptions have flourished about what we may expect with different mating systems, about the effects of inbreeding and the advantages and dangers of outbreeding. Different breeders have often secured different results with similar mating systems and the search for a rule of thumb guide has proved fruitless.

Plant mating systems and assessing population persistence in fragmented landscapes

2007 ◽  
Vol 55 (3) ◽  
pp. 239 ◽  
Author(s):  
David J. Coates ◽  
Jane F. Sampson ◽  
Colin J. Yates
Keyword(s):  
Mating System ◽  
Population Size ◽  
Mating Systems ◽  
Habitat Disturbance ◽  
Population Persistence ◽  
Population Variation ◽  
Conservation Strategies ◽  
Valuable Insight ◽  
Mixed Mating ◽  
Fragmented Landscapes

Population size and habitat disturbance are key factors likely to shape the mating system of populations in disturbed and fragmented landscapes. They would be expected to influence the availability and behaviour of the pollinator, the ability to find mates in self-incompatible species, inbreeding in self-compatible species and the size of the pollen pool. These in turn might be expected to influence key variables critical for population persistence such as seed production, seed germination and seedling fitness. Here we investigate mating-system variation in six rare species, i.e. Banksia cuneata, B. oligantha, Lambertia orbifolia (Proteaceae), Verticordia fimbrilepis subsp. fimbrilepis, Eucalyptus rameliana (Myrtaceae), Acacia sciophanes (Mimosaceae), and two common species, i.e. Calothamnus quadrifidus (Myrtaceae) and Acacia anfractuosa. All seven species are animal-pollinated relatively long-lived woody shrubs with mixed-mating systems. Population variation in mating-system parameters was investigated in relation to population size and habitat disturbance. We show that although the mating system will vary depending on pollination biology and life-history, as populations get smaller and habitat disturbance increases there is a trend towards increased inbreeding, smaller effective sizes of paternal pollen pools and greater variation in outcrossing among plants. From the species investigated in this study we have found that changes in the mating system can be useful indicators of population processes and can give valuable insight into the development of conservation strategies for the persistence of plant species following anthropogenic disturbance and landscape fragmentation.

scholarly journals EVOLUTION OF INTERACTIONS IN FAMILY-STRUCTURED POPULATIONS: MIXED MATING MODELS

Genetics ◽  
1980 ◽  
Vol 96 (1) ◽  
pp. 275-296
Author(s):  
Richard E Michod
Keyword(s):  
Mating System ◽  
Mating Systems ◽  
Random Mating ◽  
Additive Model ◽  
Multiplicative Model ◽  
Structured Populations ◽  
Mixed Mating ◽  
Genotypic Distribution ◽  
Individual Fitness ◽  
Recessive Genes

ABSTRACT The effect of inbreeding on sociality is studied theoretically for the evolution of interactions between siblings in certain mixed mating systems that give rise to inbreeding: sib with random mating and selfing with random mating. Two approaches are taken. First, specific models of altruism are studied for the various mating systems. In the case of the additive model, inbreeding facilitates the evolution of altruistic genes. Likewise, for the multiplicative model this is usually the case, as long as the costs of altruism are not too great. Second, the case of total altruism, in which the gene has zero individual fitness but increases the fitness of associates, is studied for a general fitness formulation. In this case, inbreeding often retards the ability of such genes to increase when rare, and the equilibrium frequency of those recessive genes that can increase is totally independent of the mating system and, consequently, of the amount of inbreeding. It appears from the results presented that inbreeding facilitates most forms of altruism, but retards extreme altruism. These results stem from the fact that inbreeding increases the within-family relatedness by increasing the between-family variance in allele frequency. In most cases this facilitates altruism. However, in the case of total altruism, only heterozygotes can pass on the altruistic allele, and inbreeding tends to decrease this heterozygote class. In either case, the important effect of inbreeding lies in altering the genotypic distribution of the interactions.

scholarly journals Basic Conceptual Structure of Evolutionary Ecology

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Rogério Parentoni Martins
Keyword(s):  
Evolutionary Biology ◽  
Evolutionary Ecology ◽  
Genotypic Variation ◽  
Structured Populations ◽  
Phenotypic Variance ◽  
Selective Agents ◽  
Survival And Reproduction ◽  
Environmental Variations ◽  
Successive Generations ◽  
Evolutionary Consequences

Concepts are linguistic structures with specific syntax and semantics used as sources of communicating ideas. Concepts can be simple (e.g., tree), complex (e.g., adaptation) and be part of a network of interactions that characterize an area of scientific research. The conceptual interrelationships and some evolutionary consequences upon which these interrelations are based will be addressed here. The evolutionary ecology is an area of research from the population evolutionary biology that deals mainly with the effect of positive natural selection on panmictic and structured populations. Environmental factors, conditions and variable resources in time and space, constitute the selective agents that act on the phenotypic and genotypic variation of populations in a single generation, could result in evolutionary adaptations, which are simply those traits that are most likely to confer survival and reproduction (evolutionary fitness) of the phenotypes that carry them in successive generations. The bases of adaptation are mainly genetic and transmitted vertically (classical Mendelian mechanisms) or horizontally (in the case of microorganisms). The phenotypic variance of the population is a conjoint consequence of the additive genotypic variance (heritability), nonadditive variance (dominance and epistasis), pleiotropy and the interaction between genotype and environment. The ability of the same genotype to respond to spatial environmental variations can result in phenotypic plasticity that manifests itself through reaction norms. The total phenotypic variation and its genetic and environmental components influence the ability of a population to evolve (evolvability).

2. Mating systems, or who goes with whom, and for how long

2018 ◽  
pp. 16-33
Author(s):  
Leigh W. Simmons
Keyword(s):  
Sexual Selection ◽  
Mating System ◽  
Social Relationships ◽  
Breeding Season ◽  
Mating Systems ◽  
Practical Applications ◽  
Multiple Partners ◽  
Monogamous Species ◽  
Genetic Techniques ◽  
Males And Females

‘Mating systems, or who goes with whom, and for how long’ examines the variation in how males and females associate during the breeding season, ranging from brief couplings with multiple partners to lifelong monogamy. It also shows how the discovery that females mate with many partners, even in supposedly monogamous species such as songbirds, was made possible by modern genetic techniques. Variation in mating systems holds considerable implications for the operation of sexual selection. The way that animal mating systems have been explained historically is outlined before considering how a more contemporary understanding of genetic and social relationships has reshaped our thinking and how understanding a species’ mating system can have practical applications.

When to Use Cognitive Therapy Techniques to Enhance the Effects of Exposure

2019 ◽  
pp. 175-184
Author(s):  
Carolyn Black Becker ◽  
Nicholas R. Farrell ◽  
Glenn Waller
Keyword(s):  
Eating Disorder ◽  
Cognitive Therapy ◽  
Behavioral Change ◽  
Exposure Therapy ◽  
General Rule ◽  
Careful Consideration ◽  
Rule Of Thumb ◽  
Eating Disorder Symptoms

Given that one of the main objectives of exposure therapy is to alter individuals’ cognitions related to feared stimuli, cognitive therapy can be effectively used as an adjunctive strategy to exposure. However, it is important to note that behavioral change methods show greater effectiveness in reducing eating disorder symptoms as compared to cognitive therapy. There are also circumstances in which utilizing cognitive therapy as an adjunct to exposure is not warranted. Accordingly, clinicians need to use careful consideration when deciding whether to engage eating disorder patients in cognitive therapy. As a general rule of thumb, clinicians are encouraged to employ cognitive therapy techniques when a patient is demonstrating significant hesitancy to begin exposure or is deriving notably suboptimal benefit from exposure.

scholarly journals Sequences in genetic algebras for overlapping generations

1972 ◽  
Vol 18 (1) ◽  
pp. 19-29 ◽  
Author(s):  
I. Heuch
Keyword(s):  
Probability Distribution ◽  
Discrete Time ◽  
Overlapping Generations ◽  
Mating Systems ◽  
Associative Algebras ◽  
Time Model ◽  
Discrete Time Model ◽  
Overlapping Generation ◽  
Successive Generations

When Etherington (2) introduced linear commutative non-associative algebras in connection with problems in theoretical genetics, he pointed out that various sequences of elements in these algebras represented different mating systems. In all such systems it was however assumed that the generations did not overlap, and this restriction has been kept in later work in this field. In this paper we treat sequences which make it possible to find the probability distribution in successive generations in a discrete time model where the generations may be overlapping. We also consider idempotents in genetic algebras and outline how the method used on the overlapping generation sequence may be applied to other sequences.

scholarly journals Sexual reproduction with variable mating systems can resist asexuality in a rock–paper–scissors dynamics

2015 ◽  
Vol 2 (7) ◽  
pp. 140383 ◽  
Author(s):  
Juan Carranza ◽  
Vicente Polo
Keyword(s):  
Mating System ◽  
Sexual Reproduction ◽  
Parameter Space ◽  
Mating Systems ◽  
Reproductive Mode ◽  
Long Term Effects ◽  
Diploid Population ◽  
Theoretical Question ◽  
Equal Contribution

While sex can be advantageous for a lineage in the long term, we still lack an explanation for its maintenance with the twofold cost per generation. Here we model an infinite diploid population where two autosomal loci determine, respectively, the reproductive mode, sexual versus asexual and the mating system, polygynous (costly sex) versus monogamous (assuming equal contribution of parents to offspring, i.e. non-costly sex). We show that alleles for costly sex can spread when non-costly sexual modes buffer the interaction between asexual and costly sexual strategies, even without twofold benefit of recombination with respect to asexuality. The three interacting strategies have intransitive fitness relationships leading to a rock–paper–scissors dynamics, so that alleles for costly sex cannot be eliminated by asexuals in most situations throughout the parameter space. Our results indicate that sexual lineages with variable mating systems can resist the invasion of asexuals and allow for long-term effects to accumulate, thus providing a solution to the persisting theoretical question of why sex was not displaced by asexuality along evolution.

The synthetic WROBER line – effect of the mating system on reproductive parameters and production of slaughter lambs

2016 ◽  
Vol 16 (2) ◽  
pp. 25-36
Author(s):  
Radosław Szymon Ługowski ◽  
Roman Niżnikowski ◽  
Marcin Świątek ◽  
Żaneta Szymańska ◽  
Piotr Kozera ◽  
...  
Keyword(s):  
Mating System ◽  
Mating Systems ◽  
Life Sciences ◽  
Soil Science ◽  
Meat Production ◽  
Reproductive Parameters ◽  
National Research Institute ◽  
Traditional System ◽  
Experimental Station ◽  
Plant Cultivation

The aim of the study was to compare two mating systems and their impact on reproductive parameters in sheep of the synthetic WROBER line and to evaluate the profitability of lamb meat production. Sheep were raised at the Agricultural Experimental Station in Żelazna (Warsaw University of Life Sciences) in a traditional system with mating once a year and at the Werbkowice Experimental Farm (Institute of Soil Science and Plant Cultivation – National Research Institute) in an intensified system with a shortened lambing interval. The study confirmed the suitability of the WROBER line for intensive production of slaughter lambs. In this system, 0.5 more lambs were obtained per ewe (in all seasons) than in the traditional system. Due to the increased number of lambs produced, the WROBER line can become more profitable.

scholarly journals PRIMITIVE ERYTHROPOIESIS IN EARLY CHICK EMBRYOGENESIS

1971 ◽  
Vol 50 (3) ◽  
pp. 669-681 ◽  
Author(s):  
G. Le M. Campbell ◽  
H. Weintraub ◽  
B. H. Mayall ◽  
H. Holtzer
Keyword(s):  
Cell Cycle ◽  
Progressive Increase ◽  
Cell Cycles ◽  
Proliferative Phase ◽  
Cell Divisions ◽  
Chick Embryogenesis ◽  
Interphase Cells ◽  
Feulgen Cytophotometry ◽  
Successive Generations ◽  
Primitive Erythropoiesis

Primitive erythroblasts in the circulating blood of the chick embryo continue to divide while synthesizing hemoglobin (Hb). Hb measurements on successive generations of erythroblasts show that there is a progressive increase in the Hb content of both interphase and metaphase cells. Furthermore, for any given embryo the Hb content of metaphase cells is always significantly greater than that of interphase cells. The distribution of Hb values for metaphase cells suggests that there are six Hb classes corresponding to the number of cell cycles in the proliferative phase. The location of erythroblasts in the cell cycle was determined by combining Feulgen cytophotometry with thymidine radioautography on the same cells. Measurements of the Hb content for erythroblasts in different compartments of the cell cycle (G1, S, G2, and M) show a progressive increase through the cycle. Thus, the amount of Hb per cell is a function of the number of cell divisions since the initiation of Hb synthesis and, to a lesser degree, the stage of the cell cycle. Earlier generations of erythroblasts synthesize Hb at a faster rate than the terminal generation. Several models have been proposed to explain these findings.

scholarly journals Improvement of Seed Orchard Management Based on Mating System of Cajuputi Trees

2015 ◽  
Vol 18 (1) ◽  
pp. 26 ◽  
Author(s):  
Noor Khomsah Kartikawati ◽  
Mohammad Naiem ◽  
Eko Bhakti Hardiyanto ◽  
Anto Rimbawanto
Keyword(s):  
Mating System ◽  
Mating Systems ◽  
Nuclear Dna ◽  
Environmental Changes ◽  
Seed Orchard ◽  
Genetic Potential ◽  
Genetically Improved ◽  
Viable Population ◽  
Key Words Mating System

Breeding plan of cajuputi in Indonesia is aimed to increase plantation productivity of oil yield and 1.8 cineole content. Seed orchard of cajuputi at Paliyan, Gunungkidul, established using selected and genetically improved materials, has been producing seeds for operational plantation. This seed orchard would perform optimally if the mating systems of all individuals contribute to the inheritance of all genetic potential of the offsprings. Therefore, investigation of the mating systems of cajuputi was indispensible. The study has been carried out on 10 selected mother trees and the 24 offsprings of each mother trees using 8 microsatellite markers of nuclear DNA, namely Hin-2 (100-132 bp), Hin-4 (79-114 bp), Hin-5 (128-148 bp), Hin-7 (136-224 bp), Sal-1 (93-99 bp), Sal-3 (118-219 bp), Xho-1 (96-111 bp) and Xho-4 (150-216 bp), respectively. The result showed relatively high genetic variation of the offspring (HE=0.602, HO=0.594) originated from parent trees in the seed orchard. Parent trees tend to outcross(tm=0.951, ts=0.806), although seeds originated from biparental inbred (tm – ts = 0.145) and correlated paternity(rp=0.098) have also been observed. This genetically viable population could maintain its reproduction fi tness forshort term and adapt to the dynamic environmental changes for long term. Key words: mating system, cajuputi, seed orchard, microsatellite

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