Causes and consequences of inbreeding in the banded mongoose. When these species are subjected to selfing or inbreeding they show severe reduction in vigour and fertility. Consequently, deleterious homozygotic traits that were once masked in a healthy. Cytology, inbreeding depression, and heterosis of cuphea lanceolata ait. Despite decades of research, we still have a limited understanding of the strength, underlying genetic. The genetic basis of reduced inbreeding depression in. This inbreeding depression has been well documented in many populations for a variety of traits lamberson and thomas, 1984. Heterozygosityfitness correlations and their relevance to. For example, a population of 40 adders vipera berus, shown at right experienced inbreeding depression when farming activities in sweden isolated them from other adder populations. Inbreeding depression is the decline in the value of a trait as a direct consequence of inbreeding wright, 1977. Inbreeding depression is the reduced biological fitness in a given population as a result of inbreeding, or breeding of related individuals. High inbreeding depression inbreeding leads to severe depression and exhibit lethal effects.
Mechanisms involved in the maintenance of inbreeding depression. Inbreeding coefficients f value for 66 pseudoself compatible garden and greenhouse accessions of dendranthema grandiflora tzvelv. How does inbreeding affect fitness and mate choice in. In the ants, bees, and wasps, all members of the insect order hymenoptera. Ranga agricultural university for the degree of master of science in agriculture is the result of original research work done by me. Large effects are documented in wild animal and plant populations, as well as in humans. By analogy, the term is used in human reproduction, but more commonly refers to the genetic disorders and other consequences that may arise from expression of deleterious or recessive traits resulting from incestuous sexual relationships and consanguinity. In particular, inbreeding has been found to cause a. Such inbreeding depression can affect many different. Analysis of inbreeding in a closed population of crossbred sheep by. This thesis deals with inbreeding depression, the way different mechanisms can. Severe inbreeding depression in a wild wolf canis lupus. Having to select the best plants from each population and having to make sure there is a large enough population to keep from inbreeding depression can be reason to cause depression among many home gardeners.
After 3 or 4 generations of selfing it is hard to maintain lines. Inbreeding can reduce the fitness of inbred animals beyond its negative effects on early survival, through reduced fecundity of inbred animals that survive to reproductive age. Genomics advances the study of inbreeding depression in. The most common estimates of inbreeding depression involve traits. Inbreeding depression an overview sciencedirect topics. Inbreeding depression results due to fixation of unfavourable recessive genes in f2. Notter, chairman animal science abstract genetic diversity and the effect of lamb and dam inbreeding on multiple traits were analyzed in an 11yr closed population of sheep established in 1983 and remained closed after. Taylor a thesis submitted to victoria university of wellington in fulfilment of the requirement for the degree of doctor of philosophy in ecology and. Inbreeding depression rates for two groups of maize zea mays l. Heterosis and inbreeding depression biotech articles. This suggests heterosis may be of little practical importance. Pdf the genetics of inbreeding depression researchgate.
However, identifying inbreeding depression in wild populations is challenging due to the difficulty of obtaining longterm measures of fitness and errorfree measures of. Inbreeding reduces phenotypic performance inbreeding depression and the genetic variation due to mendelian sampling among progeny of a particular set of parents. Genomics advances the study of inbreeding depression in the wild. That is with exception of the maize family, which requires 200 plants to keep from exhibiting inbreeding depression. Nine out of 16 hybrids exhibited significant inbreeding depression for primary branches. The genetic basis of reduced inbreeding depression in polyploids introduction inbreeding depression is the reduced fitness of inbred offspring relative to outbred offspring. Pdf inbreeding depression the reduced survival and fertility of offspring of related individuals occurs in wild animal and plant populations. Taylor a thesis submitted to victoria university of wellington in fulfilment of the requirement for the degree of doctor of philosophy in ecology and biodiversity victoria university of wellington. This phenomenon is observed in several other plant species that are further grouped based on the following four categories. The pedigrees contained 29,336 texel, 22,838 shropshire, and 11,487 oxford down. I certify that, with the above qualification, this thesis, and the research to which it refers, is the.
The major hurdle that must be overcome in the development of new inbred strains from wild populations is inbreeding depression which occurs most strongly between the f 2 and f 8 generations second through eighth generation of sequential brothersister mating. This inbreeding may lower the populations ability to survive and reproduce, a phenomenon called inbreeding depression. An honors thesis submitted in partial fulfillment of the requirements for honors in the. In a small population, matings between relatives are common. Inbreeding depression in the introduced spider latrodectus. Calculation and use of inbreeding coefficients for genetic. Jan 02, 2012 that is with exception of the maize family, which requires 200 plants to keep from exhibiting inbreeding depression. There is increasing awareness of the theoretical prediction that inbreeding depression does not inevitably lead to selection for inbreeding avoidance. For example, a population of 40 adders vipera berus, shown at right experienced inbreeding depression when farming activities in sweden isolated them.
In general, the higher the genetic variation or gene pool within a breeding. Graduate thesis or dissertation cytology, inbreeding. Extract three you hear common errors by more than one subject. I sincerely thank all the members of my thesis committee for their continued. The cause of this depression is the load of deleterious recessive alleles that are. Population biological fitness refers to an organisms ability to survive and perpetuate its genetic material. Pdf inbreeding depression and its evolutionary consequences. However, although there are now many studies demonstrating the existence of inbreeding depression in laboratory and captive populations, there are still relatively few. Inbreeding depression in red deer calves bmc evolutionary. Inbreeding depression is normally reduced by immigrants that are heterozygous for deleterious recessive mutations whitlock et al. Analysis of inbreeding in a closed population of crossbred sheep. Inbreeding is also an important subject in evolutionary biology as the selection pressures arising from inbreeding depression can profoundly. Inbreeding depression is often the result of a population bottleneck. Thus the objectives of this thesis were to 1 thoroughly describe the loss in.
Inbreeding depression influences lifetime breeding success in a wild population of red deer cervus elaphus. Inbreeding depression is important in the evolution of outcrossing mating systems and, because intercrossing inbred strains improves yield heterosis, which is important in crop breeding, the genetic basis of these effects has been debated since the early twentieth. This led some researchers to question whether inbreeding depression was likely to have. Graduate thesis or dissertation cytology, inbreeding depression. This work reveals that levels of inbreeding depression vary across taxa,populations and environments,but are usually substantial enough to affect both individual and population performance.
Inbreeding depression for days to 50% flowering, maturity, pods per plant, seeds per pod and seed yield per plant showed less significant difference and no significant inbreeding depression was found for plant height, pod length, pod width and 100seed weight. Mutual recognition between a mother and her offspring may also be beneficial to both parties. The main obstacle has been the construction of pedigrees necessary for calculating inbreeding coefficients. Analysis of inbreeding in a closed population of crossbred. In order to study inbreeding depression, heterosis and gene action for grain yield, biomass yield and their related characters, the present investigation was carried out utilising one double cross hybrid dhm105, one three way cross hybrid trishulata, their three parental single crosses cm 119 x cm 120, cm 211 x cm 1 and cm 1 x cm 211. Recognizing kin is important because it also allows an individual to avoid mating with closely related individuals and thus reduces inbreeding depression in offspring. In particular, inbreeding has been found to cause a decline in hatching success and early survival of the offspring of inbred mothers. Translocations and the genetic rescue of bottlenecked. Choose from 32 different sets of inbreeding depression flashcards on quizlet. However, identifying inbreeding depression in wild populations is challenging due to the difficulty of obtaining longterm measures of fitness and errorfree measures of individual inbreeding coefficients. Does maternal inbreeding lead to a reduction in egg production, either in the. Inbreeding depression the reduced survival and fertility of offspring of related individuals occurs in wild animal and plant populations as well as in humans, indicating that genetic variation.
Mechanisms involved in the maintenance of inbreeding. Measures of inbreeding inbreeding coeffi cients represent the homozygosity expected in an animals genome because of the relatedness of its parents. Oct 31, 2011 understanding the fitness consequences of inbreeding is of major importance for evolutionary and conservation biology. Detecting inbreeding depression in a severely bottlenecked, recovering species. Inbreeding depression and segregation distortion in chinook. The effects of inbreeding on disease susceptibility. In november 2003, just before plants reached maturity, a subsample of. Fitness and vigour relationship 14 inbreeding depression is the decline in fitness and vigour with decreased heterozygosity, whereas heterosis is the increase in fitness and vigour with increased heterozygosity. Inbreeding and inbreeding depression in endangered red wolves. Biomedical sciences wildlife and fisheries sciences. Inbreeding exposes deleterious recessive genes by increasing the likelihood that both of an animals copies of an allele will be the same. Graduate thesis or dissertation heterosis and inbreeding.
Inbreeding depression results due to fixation of unfavourable recessive genes in f2 fitness and vigour relationship. The inbreeding depression was of the greatest magnitude in the progeny of the early parents. Genetic diversity of white tigers and genetic factors related to coat color. In this thesis i find that inbreeding depression is not fixed but can be reduced by offspring care, which can potentially cause evolutionary feedback loops between inbreeding and care that have. The worlds most important grain crop, zea mays exhibits significant heterosis and inbreeding depression, and despite billions of. Inbreeding and inbreeding depression have been studied since the days of darwin and yet we are still making important discoveries today.
Inbreeding depression is important in the evolution of outcrossing mating systems and, because intercrossing inbred strains improves yield heterosis, which is important in crop breeding, the genetic basis of these effects has been debated since the early twentieth century. Based on degree of depression, the plant species can be grouped into four broad categories. The worlds most important grain crop, zea mays exhibits significant heterosis and inbreeding depression, and despite billions of dollars of sales and investments in. In spite of its prevalence, some researchers question whether inbreeding depression is important in wild populations, invoking two main arguments.
Empirically quantifying the effects of inbreeding on parasite resistance is therefore important for exsitu conservation of vertebrates. Inbreeding depression and its converse, heterosis, are genetic phenomena. For example, despite a wealth of knowledge about the effects of inbreeding under laboratory conditions, until relatively recently there has been little evidence of inbreeding depression in wild populations. Inbreeding depression in the introduced spider latrodectus geometricus.
J slate, l e kruuk, t c marshall, j m pemberton, and t h cluttonbrock institute of cell, animal and population biology, university of edinburgh, uk. Causes and consequences of inbreeding in the banded. Determining which hypo thesis is the most likely ex planation for hfcs observed in a real population provides insights into the importance of genetic causes of reduced fitness in wild populations. Inbreeding depression reduced fitness of individuals with related parents has long been a major focus of ecology, evolution, and conservation biology. Thus, detecting inbreeding depression is important for population viability assessment and conservation management.
Surprisingly little is known about the severity of inbreeding depression in the wild, in part because it is very difficult to measure individual inbreeding in natural populations. Inbreeding depression refers to the reduced vigor in the offspring from matings involving related parents. However, outcrossing can reduce mean population fitness if hybridization disrupts coadapted gene complexes or favorable epistatic interactions. Heterosis or hybrid vigor is a phenomenon in which the f1 progeny is superior in characteristics than its inbred parents. The advantages and disadvantages of selffertilization. A few years ive been sending hadnt been learning studying had been bomb explosions in the afternoon. Know about inbreeding and inbreeding depression, along with the degrees of depression. Inbreeding may or may not lead to inbreeding depression, which is a reduction in the fitness in the offspring produced by inbred matings. Inbreeding depression occurs because matings between relatives lead to an increase in homozygosity.
Although any of these genetic mechanisms could threaten population persistence, inbreeding poses the most immediate risk. Graduate thesis or dissertation heterosis and inbreeding in. Inbreeding trend and inbreeding depression in the danish. Inbreeding depression another important consequence ofsmall population size is inbreeding, defined as mating between related individuals hartl and clark 1989. Progeny size at three life cycle stages seed set, germination.
Learn inbreeding depression with free interactive flashcards. Postzygotic inbreeding depression in chrysanthemums dendranthema grandiflora, d. Heterosis is defined as the superiority of f1 hybrid over both the parents in terms of yield andor some other characters. The objective of this thesis was to examine both the consequences of severe bottlenecks and the use of translocations to ameliorate the effects of inbreeding due to bottlenecks. Detecting inbreeding depression in a severely bottlenecked. This thesis deals with inbreeding depression, the way different mechanisms can maintain large levels of inbreeding depression and its importance in the maintenance of gynodioecy. Mar 22, 2005 a pedigree, inbreeding coefficients and litter sizes. Inbreeding results in an increase in homozygosity among loci within progeny, including homozygosity ofrare, recessive deleterious alleles hartl and clark 1989. Cross pollinated species and species reproducing asexually are highly heterozygous. As matings in small populations occur among a lower number of mates, this increases the chance of matings among relatives, and as inbreeding is known to cause decreased fitness in populations of many species e. The genetic architecture of inbreeding depression and the effects of inbreeding depression on.
Inbreeding depression loss or decrease in vigor due to inbreeding. However, there are few studies using pedigreebased estimates of inbreeding or investigating the influence of environment and age variation on inbreeding depression in natural populations. Heterosis breeding and inbreeding depression authorstream. I examined the underlying causes of maternal inbreeding depression by observing the effects of one generation of fullsibling mating on lifehistory and physiological traits in the zebra finch. We used next generation sequencing technologies and a sample of the most elite publicly. Inbreeding depression influences lifetime breeding success. The level of inbreeding depression has been suggested to determine a plants mating. The aim of this project was to elucidate the mechanisms behind maternal inbreeding depression, using a model avian species, the zebra finch taeniopygia guttata. Inbreeding is the production of offspring from the mating or breeding of individuals or organisms that are closely related genetically. Inbreeding depression is the reduced survival and fertility of offspring of related individuals. The objective of this study was to analyze the development of inbreeding and estimate inbreeding depression in the danish populations of 3 major meat type sheep breeds. These discoveries can inform conservation practices as inbreeding depression can contribute to population extinction. Inbreeding is a widespread phenomenon that can decrease fitness.
912 851 528 925 1536 915 1623 1395 627 843 131 119 1096 1222 1414 469 1359 498 1187 1356 1523 147 934 917 749 804 524 71 1588 637 1609 1467 1129 355 490 481 1390 614 1125 729 1119 820 340 607 1461 580