DOCSLIB.ORG

The Effect of Inbreeding on Longevity, Fertility, and Disability

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Effect of Inbreeding on Longevity, Fertility, and Disability The effect of inbreeding on longevity, fertility and disability Background Children of consanguineous relationships are likely to have an increased level of homo-zygotic alleles which cause a greater risk for the manifestation of recessive genetic disorders. In the study area chosen here, Skellefteå in Sweden, the level of consanguineous marriages where relatively high. We can also trace the family history back several hundred years making it possible to create pedigrees for the population and to calculate the level of inbreeding. This makes the studied area suitable for investigating the effect of inbreeding. Many genetic disease, both autosomal recessive and autosomal dominant, have a rather high frequency in Skellefteå. Earlier studies have shown an effect of inbreeding on fertility and lifespan. An example of this is Helgason et al., 2008 who showed that for the Icelandic population there was an effect on fertility and lifespan of an individual from the level of inbreeding. This study complement such studies by analyzing the effect of inbreeding on fertility and longevity in a Swedish setting and by adding the outcome variable disability which has not been considered in a historical context before. Bittles, A. and I. Egerbladh (2005) discuss the potential effect of inbreeding on genetic disorders in the Skellefteå region but do not explicitly link inbreeding and disabilities using data as we attempt in this study. The aim of the paper is thus to investigate if inbreeding had any effects on individuals living in Skellefteå during the 19th century. In particular the effect on longevity, fertility and disabilities will be investigated. Method The degree of inbreeding is measured by the inbreeding coefficient which is a measure that increases the more inbred an individual is and is denoted as F (Ballou, 1983). To exemplify, Full siblings get an F of 1/4, First Cousins 1/16, Second Cousins 1/64 and Third Cousins 1/256. F is then related, as an explanatory variable, to outcomes indicating longevity, fertility and presence of disabilities. Longevity is measured as life-length (number of lived days) and the modeling approach will be Cox regression. Fertility will be measured by number of children a person has and the modeling approach will be based on Poisson regression and related methods. The effect on disability will be analyzed both by using the presence of disability as the outcome and by analyzing different disability groups separately. Here the modeling approach will be logistic regression. Data The data sources consist of parish registers stored at the Demographic Data Base (DDB) at Umeå University and these registers provide digitized and linked parish records comprised by original registers for parishioners’ birth, baptism, marriage, out- or in-migration, death, burial and the catechetical examination records. The registers are extracted and digitized from chosen parishes in Sweden during the seventeenth and nineteenth centuries and are linked on individual level, which give us extensive demographic information about each parishioners life. (Vikström et.al., 2006) The catechetical examination registers are the major source for identifying disabilities and for following individuals over a lifetime to note fertility and longevity. These registers were collected on yearly basis due to the obligation for the ministers to keep records of the parishioners’ knowledge of the catechism and their reading ability, first stated in the Church law of 1686. (Nilsdotter, 2014) In these records the ministers also made other notes, such as marks of impairments (lytesmarkeringar), which document disabilities among the parishioners. These notes report limits in peoples’ physical and mental function. The ministers’ marks of impairments are used to identify the disabled individuals and to separate them from the non-disabled cases. (Haage, 2012) The data extracted consists of observations of individuals which at some point in their lives lived in Skellefteå during the time the church records were kept. Table 1 contains the number of people and their inbreeding coefficient and Figure 1 histograms over observed inbreeding coefficients. The variables available are the date of birth, the individuals id, the individuals parents ids, what kind of entry into/exit from the church records, which date the entry is made and which sex each individual is. From these variables the following variables can be identified or calculated: day of birth, age of death, number of children, individual inbreeding coefficient (IIC), and mean inbreeding coefficient of children (MICC). Table 1: Number and proportion of individuals in data depending on their inbreeding coefficient. Figure 1: Distribution of inbreeding coefficients for individuals. Results 1.Longevity Figure 2 shows the Kaplan-Meier curves for the genders and different inbreeding groups. It shows a higher mortality for men and for the more inbreed groups. The Cox regression model presented in Table 2 confirms this with a significant effect on the lifespan from the level of inbreeding an individual has. An individual whose parents are second cousins or more closely related has a higher risk of dying than individuals with no inbreeding. The estimated β coefficients for the two levels were 0.1640 and 0.2573 for second cousins and first cousins respectively. By taking the exponent of these coefficients we get estimates of the probability of dying relative to the base level of not being inbred. Doing this shows that the probability of dying for second cousins compared to individuals with no inbreeding is 1.1782 times higher given that they are of the same sex. In the same way for first cousins the probability of dying is 1.2934 times higher. Helgason et al. 2008 showed that for the Icelandic population the life expectancy of children of couples who were related as second cousins or closer was shorter than for couples with less inbreeding. Since both their study and this study of the population of Skellefteå during the 19th century one could argue that these results a good indication of how inbreeding affects the lifespan of individuals. The risk of dying also lower for women compared to men as expected where the estimated β coefficient was -0.1128. Figure 2. Kaplan-Meier plot for categorical covariates. Table 2. Results of Cox regression 2. Fertility Using Poisson regression, no effect of inbreeding on the fertility of the women were found. The results of the regression is not shown, instead the descriptives in Figure 3 are shown which might indicate a slightly higher fertility, though not significant, in consanguineous relationships where the inbreeding is low but above zero. This indicates that inbreeding did not have a major affect on fertility in Skellefteå during the 19th century which is unlike the results of Helgason et al. 2008 on the Icelandic population which showed that the mean number of children increase in consanguineous relationships. Figure 3. Fertility and level of inbreeding 3. Disabilities This part is yet to be finalized but we suspect that we might see an increasing propensity for disability with increasing inbreeding coefficient. Logistic regression will here be used for the analysis. References Ballou, J. (1983). Calculating inbreeding coeicients from pedigrees. Genetics and conservation: a reference for managing wild animal and plant populations, 509-520. Bittles, A. and I. Egerbladh (2005). The inluence of past endogamy and consanguinity on genetic disorders in northern sweden. Annals of human genetics 69(5), 549-558. Pär Vikström, Anders Brändström and Sören Edvinsson, “Longitudinal Databases: Sources for Analyzing the Life-Course,” History and Computing, 14 (2006): 109–128. Haage, Helena. (2012) “Identifying Disability using Nineteenth Century Parish Registers.” (Unpublished paper Umeå University2012). Helgason, A., S. Pálsson, D. F. Guðbjartsson, K. Stefánsson, et al. (2008). An association between the kinship and fertility of human couples. Science 319 (5864), 813#816. Nilsdotter Jeub, Ulla (2009) Parish Records, Digitalised Material from Demographic Data Base. (Umeå: Umeå University 2009), accessed November 24, 2014, http://www.ddb.umu.se/digitalAssets/37/37716_parishrecords.pdf..
Load more

Recommended publications
  • Autism, Genetics, and Inbreeding: an Evolutionary View
    Vol. 8(5), pp. 67-71, May 2016 DOI: 10.5897/JPHE2015.0764 Article Number: 5670C9357949 Journal of Public Health and ISSN 2141-2316 Copyright © 2016 Epidemiology Author(s) retain the copyright of this article http://www.academicjournals.org/JPHE Review Autism, genetics, and inbreeding: An evolutionary view Alex S. Prayson National Council on Rehabilitation Education Received 18 July, 2015; Accepted 22 January, 2016 Recently there have been increased reports of autism, yet the disease is not contagious. Since it is not catching, there must be other forces at work that somehow create or pass on the autistic symptoms. DNA reports show that deviations in the genetic code due to ancient inbreeding can follow a human line for generations. Studies show that inbreeding was widespread until a few hundred years ago and is continued today, but to a lesser degree. After millions of inbreeds, the world population has become so numerous that it is globally sharing ancestors which is producing genetic abnormalities. In other words, autism may be the result of the widespread inbreeding of ancient generations. We are all touched by autism to one degree or another through common ancestors. The DNA of modern Homo sapiens of European and/or Asian descent will show 1 to 4% Neanderthal from 40,000 years ago. With that in mind, todays outbreaks may be due to descendants of ancient inbreeding times surfacing at the same time. Key words: Autism, genetics, inbreeding, DNA, ancient generations, consanguineous marriage, incest INTRODUCTION The world might be smaller than you think chances of inheriting a bad DNA fit which results in a birth defect.
    [Show full text]
  • Cousin Marriage & Inbreeding Depression
    Evidence of Inbreeding Depression: Saudi Arabia Saudi Intermarriages Have Genetic Costs [Important note from Raymond Hames (your instructor). Cousin marriage in the United States is not as risky compared to cousin marriage in Saudi Arabia and elsewhere where there is a long history of repeated inter-marriage between close kin. Ordinary cousins without a history previous intermarriage are related to one another by 0.0125. However, in societies with a long history of intermarriage, relatedness is much higher. For US marriages a study published in The Journal of Genetic Counseling in 2002 said that the risk of serious genetic defects like spina bifida and cystic fibrosis in the children of first cousins indeed exists but that it is rather small, 1.7 to 2.8 percentage points higher than for children of unrelated parents, who face a 3 to 4 percent risk — or about the equivalent of that in children of women giving birth in their early 40s. The study also said the risk of mortality for children of first cousins was 4.4 percentage points higher.] By Howard Schneider Washington Post Foreign Service Sunday, January 16, 2000; Page A01 RIYADH, Saudi Arabia-In the centuries that this country's tribes have scratched a life from the Arabian Peninsula, the rule of thumb for choosing a marriage partner has been simple: Keep it in the family, a cousin if possible, or at least a tribal kin who could help conserve resources and contribute to the clan's support and defense. But just as that method of matchmaking served a purpose over the generations, providing insurance against a social or financial mismatch, so has it exacted a cost--the spread of genetic disease.
    [Show full text]
  • Genetic and Epigenetic Regulation of Phenotypic Variation in Invasive Plants – Linking Research Trends Towards a Unified Fr
    A peer-reviewed open-access journal NeoBiota 49: 77–103Genetic (2019) and epigenetic regulation of phenotypic variation in invasive plants... 77 doi: 10.3897/neobiota.49.33723 REVIEW ARTICLE NeoBiota http://neobiota.pensoft.net Advancing research on alien species and biological invasions Genetic and epigenetic regulation of phenotypic variation in invasive plants – linking research trends towards a unified framework Achyut Kumar Banerjee1, Wuxia Guo1, Yelin Huang1 1 State Key Laboratory of Biocontrol and Guangdong Provincial Key Laboratory of Plant Resources, School of Life Sciences, Sun Yat-sen University 135 Xingangxi Road, Guangzhou, Guangdong, 510275, China Corresponding author: Yelin Huang ([email protected]) Academic editor: Harald Auge | Received 7 February 2019 | Accepted 26 July 2019 | Published 19 August 2019 Citation: Banerjee AK, Guo W, Huang Y (2019) Genetic and epigenetic regulation of phenotypic variation in invasive plants – linking research trends towards a unified framework. NeoBiota 49: 77–103. https://doi.org/10.3897/ neobiota.49.33723 Abstract Phenotypic variation in the introduced range of an invasive species can be modified by genetic variation, environmental conditions and their interaction, as well as stochastic events like genetic drift. Recent stud- ies found that epigenetic modifications may also contribute to phenotypic variation being independent of genetic changes. Despite gaining profound ecological insights from empirical studies, understanding the relative contributions of these molecular mechanisms behind phenotypic variation has received little attention for invasive plant species in particular. This review therefore aimed at summarizing and synthesizing information on the genetic and epige- netic basis of phenotypic variation of alien invasive plants in the introduced range and their evolutionary consequences.
    [Show full text]
  • Inbreeding Effects in Wild Populations
    230 Review TRENDS in Ecology & Evolution Vol.17 No.5 May 2002 43 Putz, F.E. (1984) How trees avoid and shed lianas. estimate of total aboveground biomass for an neotropical forest of French Guiana: spatial and Biotropica 16, 19–23 eastern Amazonian forest. J. Trop. Ecol. temporal variability. J. Trop. Ecol. 17, 79–96 44 Appanah, S. and Putz, F.E. (1984) Climber 16, 327–335 52 Pinard, M.A. and Putz, F.E. (1996) Retaining abundance in virgin dipterocarp forest and the 48 Fichtner, K. and Schulze, E.D. (1990) Xylem water forest biomass by reducing logging damage. effect of pre-felling climber cutting on logging flow in tropical vines as measured by a steady Biotropica 28, 278–295 damage. Malay. For. 47, 335–342 state heating method. Oecologia 82, 350–361 53 Chai, F.Y.C. (1997) Above-ground biomass 45 Laurance, W.F. et al. (1997) Biomass collapse in 49 Restom, T.G. and Nepstad, D.C. (2001) estimation of a secondary forest in Sarawak. Amazonian forest fragments. Science Contribution of vines to the evapotranspiration of J. Trop. For. Sci. 9, 359–368 278, 1117–1118 a secondary forest in eastern Amazonia. Plant 54 Putz, F.E. (1983) Liana biomass and leaf area of a 46 Meinzer, F.C. et al. (1999) Partitioning of soil Soil 236, 155–163 ‘terra firme’ forest in the Rio Negro basin, water among canopy trees in a seasonally dry 50 Putz, F.E. and Windsor, D.M. (1987) Liana Venezuela. Biotropica 15, 185–189 tropical forest. Oecologia 121, 293–301 phenology on Barro Colorado Island, Panama.
    [Show full text]
  • Inbreeding Effects in the Epigenetic
    CORRESPONDENCE LINK TO ORIGINAL ARTICLE protein modifications, chromatin structure and RNA interference — all of which Inbreeding effects in the are closely connected epigenetic processes — are therefore crucial for deciphering the epigenetic era underlying genetic causes of inbreeding effects that occur during embryonic develop- Christian Biémont ment and in adulthood. This should shed new light on an old problem that is still at the forefront of population genetic investigation. Recent articles by Charlesworth and Willis been clearly established that deficiencies (The genetics of inbreeding depression. in DNA methylation (mostly CG, but also Christian Biémont is at the Laboratoire de Biométrie et 1 Biologie Evolutive, UMR 5558, Centre National de la Nature Rev. Genet. 10, 783–796 (2009)) non-CG in some organisms) are deleteri- Recherche Scientifique, Université de Lyon, 2 10,11 and Kristensen et al. have summarized the ous and lead to early embryo mortality . Université Lyon 1. F-69622, Villeurbanne, France. theoretical basis of inbreeding depression Furthermore, the unmethylated mutants e-mail: [email protected] (the deleterious effects of crossing related that survive exhibit developmental aberra- individuals). Although overdominance tions of progressive severity as a result of 1. Charlesworth, D. & Willis, J. H. The genetics of inbreeding depression. Nature Rev. Genet. 10, 12,13 (the fact that heterozygotes are fitter than inbreeding . It therefore seems that any 783–796 (2009). homozygotes) cannot be entirely ruled mutation that leads to the misexpression 2. Kristensen, T. N., Pedersen, K. S., Vermeulen, C. J. & Loeschcke, V. Research on inbreeding in the ‘omic’ era. out, the expression of recessive deleterious of genes involved in epigenetic control will Trends Ecol.
    [Show full text]
  • Population Structure, Genetic Diversity, and Gene Introgression of Two Closely Related Walnuts (Juglans Regia and J
    Article Population Structure, Genetic Diversity, and Gene Introgression of Two Closely Related Walnuts (Juglans regia and J. sigillata) in Southwestern China Revealed by EST-SSR Markers Xiao-Ying Yuan, Yi-Wei Sun, Xu-Rong Bai, Meng Dang, Xiao-Jia Feng, Saman Zulfiqar and Peng Zhao * Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, College of Life Sciences, Northwest University, Xi’an 710069, China; [email protected] (X.-Y.Y.); [email protected] (Y.-W.S.); [email protected] (X.-R.B.); [email protected] (M.D.); [email protected] (X.-J.F.); [email protected] (S.Z.) * Correspondence: [email protected]; Tel./Fax: +86-29-88302411 Received: 20 September 2018; Accepted: 12 October 2018; Published: 16 October 2018 Abstract: The common walnut (Juglans regia L.) and iron walnut (J. sigillata Dode) are well-known economically important species cultivated for their edible nuts, high-quality wood, and medicinal properties and display a sympatric distribution in southwestern China. However, detailed research on the genetic diversity and introgression of these two closely related walnut species, especially in southwestern China, are lacking. In this study, we analyzed a total of 506 individuals from 28 populations of J. regia and J. sigillata using 25 EST-SSR markers to determine if their gene introgression was related to sympatric distribution. In addition, we compared the genetic diversity estimates between them. Our results indicated that all J. regia populations possess slightly higher genetic diversity than J. sigillata populations. The Geostatistical IDW technique (HO, PPL, NA and PrA) revealed that northern Yunnan and Guizhou provinces had high genetic diversity for J.
    [Show full text]
  • A Comparison of Pedigree- and DNA-Based Measures for Identifying Inbreeding Depression in the Critically Endangered Attwater's Prairie-Chicken
    Molecular Ecology (2013) 22, 5313–5328 doi: 10.1111/mec.12482 A comparison of pedigree- and DNA-based measures for identifying inbreeding depression in the critically endangered Attwater’s Prairie-chicken SUSAN C. HAMMERLY,* MICHAEL E. MORROW† and JEFF A. JOHNSON* *Department of Biological Sciences, Institute of Applied Sciences, University of North Texas, 1155 Union Circle, #310559, Denton, TX 76203, USA, †United States Fish and Wildlife Service, Attwater Prairie Chicken National Wildlife Refuge, PO Box 519, Eagle Lake, TX 77434, USA Abstract The primary goal of captive breeding programmes for endangered species is to prevent extinction, a component of which includes the preservation of genetic diversity and avoidance of inbreeding. This is typically accomplished by minimizing mean kinship in the population, thereby maintaining equal representation of the genetic founders used to initiate the captive population. If errors in the pedigree do exist, such an approach becomes less effective for minimizing inbreeding depression. In this study, both pedigree- and DNA-based methods were used to assess whether inbreeding depression existed in the captive population of the critically endangered Attwater’s Prairie-chicken (Tympanuchus cupido attwateri), a subspecies of prairie grouse that has experienced a significant decline in abundance and concurrent reduction in neutral genetic diversity. When examining the captive population for signs of inbreeding, vari- f ation in pedigree-based inbreeding coefficients ( pedigree) was less than that obtained f from DNA-based methods ( DNA). Mortality of chicks and adults in captivity were also r f positively correlated with parental relatedness ( DNA) and DNA, respectively, while no correlation was observed with pedigree-based measures when controlling for addi- tional variables such as age, breeding facility, gender and captive/release status.
    [Show full text]
  • Inbreeding Depression in Conservation Biology
    P1: FOF September 25, 2000 9:54 Annual Reviews AR113-07 Annu. Rev. Ecol. Syst. 2000. 31:139–62 Copyright c 2000 by Annual Reviews. All rights reserved INBREEDING DEPRESSION IN CONSERVATION BIOLOGY Philip W. Hedrick Department of Biology, Arizona State University, Tempe, Arizona 85287; email: [email protected] Steven T. Kalinowski Conservation Biology Division, National Marine Fisheries Service, 2725 Montlake Blvd. East, Seattle, Washington 98112; email: [email protected] Key Words endangered species, extinction, fitness, genetic restoration, purging ■ Abstract Inbreeding depression is of major concern in the management and con- servation of endangered species. Inbreeding appears universally to reduce fitness, but its magnitude and specific effects are highly variable because they depend on the genetic constitution of the species or populations and on how these genotypes interact with the environment. Recent natural experiments are consistent with greater inbreeding depression in more stressful environments. In small populations of randomly mating individuals, such as are characteristic of many endangered species, all individuals may suffer from inbreeding depression because of the cumulative effects of genetic drift that decrease the fitness of all individuals in the population. In three recent cases, intro- ductions into populations with low fitness appeared to restore fitness to levels similar to those before the effects of genetic drift. Inbreeding depression may potentially be reduced, or purged, by breeding related individuals. However, the Speke’s gazelle example, often cited as a demonstration of reduction of inbreeding depression, appears to be the result of a temporal change in fitness in inbred individuals and not a reduction in inbreeding depression.
    [Show full text]
  • Genetic Background and Inbreeding Depression in Romosinuano Cattle Breed in Mexico
    animals Article Genetic Background and Inbreeding Depression in Romosinuano Cattle Breed in Mexico Jorge Hidalgo 1 , Alberto Cesarani 1 , Andre Garcia 1, Pattarapol Sumreddee 2, Neon Larios 3 , Enrico Mancin 4, José Guadalupe García 3,*, Rafael Núñez 3 and Rodolfo Ramírez 3 1 Department of Animal and Dairy Science, University of Georgia, Athens, GA 30602, USA; [email protected] (J.H.); [email protected] (A.C.); [email protected] (A.G.) 2 Department of Livestock Development, Bureau of Biotechnology in Livestock Production, Pathum Thani 12000, Thailand; [email protected] 3 Departamento de Zootecnia, Posgrado en Producción Animal, Universidad Autónoma Chapingo, Chapingo 56230, Mexico; [email protected] (N.L.); [email protected] (R.N.); [email protected] (R.R.) 4 Department of Agronomy, Food, Natural Resources, Animals and Environment-DAFNAE, University of Padova, Viale dell’Università 16, 35020 Legnaro, Italy; [email protected] * Correspondence: [email protected] Simple Summary: The objective of this study was to evaluate the genetic background and inbreeding depression in the Mexican Romosinuano cattle using pedigree and genomic information. Inbreeding was estimated using pedigree (FPED) and genomic information based on the genomic relationship matrix (FGRM) and runs of homozygosity (FROH). Linkage disequilibrium (LD) was evaluated using the correlation between pairs of loci, and the effective population size (Ne) was calculated based on LD and pedigree information. The pedigree file consisted of 4875 animals; 71 had genotypes. Citation: Hidalgo, J.; Cesarani, A.; LD decreased with the increase in distance between markers, and Ne estimated using genomic Garcia, A.; Sumreddee, P.; Larios, N.; information decreased from 610 to 72 animals (from 109 to 1 generation ago), the Ne estimated using Mancin, E.; García, J.G.; Núñez, R.; pedigree information was 86.44.
    [Show full text]
  • Impact of Consanguineous Marriages and Degrees of Inbreeding On
    nature publishing group Articles Population Study Impact of consanguineous marriages and degrees of inbreeding on fertility, child mortality, secondary sex ratio, selection intensity, and genetic load: a cross-sectional study from Northern India Mohd Fareed1, Mir Kaisar Ahmad2, Malik Azeem Anwar1 and Mohammad Afzal1 BACKGROUND: The aim of our study was to understand the health services has been found to be more frequent among low relationship between consanguineous marriages and repro- socioeconomic and uneducated families (1). ductive outcomes. Consanguineous marriages have been practised for thou- METHODS: A total of 999 families were recruited from five sands of years in many communities throughout the world. Muslim populations of Jammu region. Family pedigrees were The prevalence of consanguinity varies among different coun- drawn to access the family history and inbreeding status in tries, usually associated with different demographic features, terms of coefficient of inbreeding (F). Fertility, mortality, sec- such as religion, education, SES, geography and size of the ondary sex ratio, selection intensity, and lethal equivalents area, isolation of the population, and living in rural or urban were measured using standard methods. set up (2). Parental consanguinity has been associated with RESULTS: The significant differences for gross fertility was stillbirths, low birth weight, preterm delivery, abortion, infant found to be higher among inbred groups as compared to the and child mortality, congenital birth defects, cognitive impair- unrelated families (P < 0.05) and higher mortality rates were ments, cardiovascular risks, malformations, and several other observed among consanguineous families of all populations complex disorders (3–10). in comparison with the non-consanguineous family groups.
    [Show full text]
  • 0 Inbreeding and Population Structure. [This Chapter Is Just Barely Started and Does Not Yet Have a Particular "Case Study" Associated with It
    Case Studies in Ecology and Evolution DRAFT 0 Inbreeding and Population Structure. [This chapter is just barely started and does not yet have a particular "case study" associated with it. But I'm going to post this anyway in case you find this useful for reviewing your lecture notes.] The Hardy Weinberg Equilibrium was defined for the case of random mating. However it is rare that individuals in a population truly mate at random1. For populations with spatial structure, individuals are more likely to mate with others that are nearby than with individuals from more distant sites. Although it would be nice to define a population as the collection of individuals that are mating together randomly, the boundaries of a population are often very indistinct. A plant that is growing on one side of a meadow is much more likely to pollinate others growing nearby, so in that sense two sides of a meadow may be genetically separated. But when the plants are scattered evenly across that meadow, where would you draw the boundary? In addition, there may be behavioral patterns that cause individuals to mate non- randomly. If individuals live in family structured groups they may be likely to mate with relatives. An extreme form of non-random mating occurs in plants that routinely self- fertilize. The result is that populations are often genetically structured, at a variety of scales. Behavioral traits may result in individuals that are inbred with respect to the local subpopulation. And spatial separation may result in sub-populations that are "inbred" with respect to the population as a whole.
    [Show full text]
  • ON SELECTION for INBREEDING in POLYGYNOUS Clutton
    Heredity (1979), 43 (2), 205-211 ON SELECTION FOR INBREEDING IN POLYGYNOUS ANIMALS ROBERTH. SMITH Wildlife Management Group, Department of Zoology, University of Reading, Berkshire RG6 2Aj Received11 .iii. 11 SUMMARY It is assumed by many zoologists that most animals avoid inbreeding because of the associated deleterious effects. The breeding behaviour of fallow deer is described and shown to make a father-daughter incest likely. By treating incest as a form of altruistic behaviour on the part of females, an inclusive fitness argument is developed to account for incest in polygynous species. It is shown that a substantial (1/3) reduction in individual fitness is required if incest is to be selected against. 1. INTRODUCTION INBREEDING in animals is generally thought of as being in some sense dis- advantageous, particularly when it is as extreme as incest between parents and offspring or between sibs (e.g.Bodmerand Cavalli-Sforza, 1976; Clutton-Brock and Harvey, 1976; Wilson, 1975). On the other hand botanists do not seem too surprised that there are plants in which self- fertilisation is normal or even obligatory (Berry, 1977). Detrimental effects of inbreeding are well known to animal breeders and are usually thought to result from increased homozygosity of deleterious recessive alleles. Many zoologists assume that the detrimental effects of inbreeding have, by natural selection, led to the evolution of outbreeding mechanisms. Thus 700logists tend to look for behavioural mechanisms of outbreeding, and often seem to find them. However, so-called outbreeding behaviour is often just dispersal of one of the sexes and other explanations, such as male-female conflict in breeding behaviour or avoidance of competition between parent and offspring, are usually overlooked.
    [Show full text]