5 - Population Persistance

Goes between 0 and 1 10 genotype frequency outbred f0

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Unformatted text preview: ) 0.8 0.6 0.4 0.2 0.0 aa Aa AA Genotype M5.13 Bio 3115 Université d’Ottawa / University of Ottawa Increase in homozygosity under different degrees of inbreeding, according to the degree of relatedness between parents Percent Homozygotes 100 Self-fertilization 90 Brother and s ister Double first cousins 80 70 First cousins 60 Second cousins 50 0 2 4 6 8 10 12 14 Generation M5.14 Bio 3115 Université d’Ottawa / University of Ottawa M5 2009-2010.7 BIO 3115 Conservation Biology 7 No effects of inbreeding (4 populations) 6 5 4 3 2 90 100 80 70 60 50 40 30 20 0 0 1 10 Since inbreeding decreases heterozygosity, many congenital diseases which are not expressed in heterozygous form are now expressed. This may result in reduced fertility or increased offspring/juvenile mortality (inbreeding depression) which can immediately affect the population growth rate. % Increase in juvenile mortality M5.15 Bio 3115 Université d’Ottawa / University of Ottawa Effects of inbreeding on juvenile mortality in captive populations of mammals In virtually all captive populations, inbreeding results in increased juvenile mortality relative to outbred populations 70 % Juvenile mortality outbred Number of populations Consequences of small Ne II: inbreeding depression Ungulates Primates Small mammals 60 50 40 30 20 10 0 0 20 40 60 80 100 % Juvenile mortality - inbred M5.16 Bio 3115 Université d’Ottawa / University of Ottawa M5 2009-2010.8 BIO 3115 Conservation Biology Population genetic effects of inbreeding versus genetic drift (both arise from small effective population sizes!) Comparison Inbreeding Genetic Drift Allele frequencies Unchanged Altered Increased population homozygosity Yes Yes Both homozygotes present Yes (at equilibrium) No (only one) M5.17 Bio 3115 Université d’Ottawa / University of Ottawa The smaller the population, the faster the rate of loss of genetic variability. Variation is lost through a combination of genetic drift and inbreeding. Ne=1 Ne=2 % original variation remaining Loss of genetic variability in small populations Ne=10 Ne=100 100 90 80 70 60 50 40 30 20 10 0 0 1 2 3 4 5 6 7 8 9 10 11 12 Generations M5.18 Bio 3115 Université d’Ottawa / University of Ottawa M5 2009-2010.9 BIO 3115 Conservation Biology The Founder Effect Colonization of an isolated area by a small number of individuals, that carry a small fraction of the genetic variation of the parental population Rare alleles in the ancestral population are usually lost because no successful colonists carry them Due to small initial effective size of colonizing population, genetic divergence from the ancestral population occurs via drift, and reduced heterozygosity in colonizing population. M5.19 Population bottlenecks and founder effects a population bottleneck occurs when a population experiences a severe, temporary reduction...
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This document was uploaded on 03/11/2014 for the course BIO 3115 at University of Ottawa.

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