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Genetic Diversity

Genetic Diversity. Factors that make populations vulnerable to extinction. Environmental fluctuations Catastrophes Demographic uncertainties Genetic problems Habitat fragmentation. Heath Hen – Extinction Vortex. Minimum Viable Population Size.

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Genetic Diversity

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  1. Genetic Diversity

  2. Factors that make populations vulnerable to extinction • Environmental fluctuations • Catastrophes • Demographic uncertainties • Genetic problems • Habitat fragmentation

  3. Heath Hen – Extinction Vortex

  4. Minimum Viable Population Size • Another definition - often defined as 95% probability of 100 year survival, but can also plan for longer survival (500 or 1000 years) • MVP is usually determined by modeling

  5. Forces which may cause extinction 1) deterministic - something essential is removed (habitat loss) or something lethal is added (pollutant, disease, introduced species) - presumably we can act to minimize these risks

  6. Forces which may cause extinction 2) stochastic (random) - environmental, catastrophic, demographic and genetic - this is what we need to worry about and what is hardest to prevent • environmental randomness effects resources and conditions and we can't do much about it • catastrophic randomness - floods, fires, hurricanes, volcanoes - can't really prevent but can spread individuals around to minimize the impact • demographic - just natural random variation in birth and death rates can lead to extinction • genetic - lack of genetic variability can lead to problems of inbreeding and poor response to diseases and environmental change

  7. Bighorn Sheep and MVP

  8. Bighorn Sheep and MVP

  9. Grizzly Bear and 50/500 Rule

  10. MVP – 50/500 Rule?

  11. Reductions in Polymorphism Reductions in population size can lead to losses of genetic polymorphism Two special cases of reductions in population size are: • A few individuals move to a new area and start a new population that is isolated from other populations – founder effect • We can also experience a population bottleneck where a formerly large population is drastically reduced in size

  12. Founder Effect – Galapagos Tortoise

  13. Founder effect – Amish and Polydactyly

  14. Population Bottleneck – Northern Elephant Seal

  15. Reductions to Polymorphism • Genetic drift - random changes in gene frequency in a population – nondirectional evolutionary change which occurs due to sampling errors in mating and mortality -can result in a loss of polymorphism

  16. Effective Population Size • Effective population size - the number of reproductive individuals within a population taking into account unequal representation of the sexes in reproduction or unequal representation of generations over time

  17. Sewall Wright at University of Chicago In 1928

  18. Sewall Wright in 1980’s

  19. Effective Population Size in theSocial Tuco-Tuco

  20. Effective Population Size in theSocial Tuco-Tuco

  21. Using a pedigree chain to calculate inbreeding

  22. Inbreeding in European Royalty

  23. Gene Flow • The movement of alleles from one population to another

  24. Rates of Gene Flow – Ne (effective population size) = 120

  25. Gene Flow in Conifers

  26. Gene Flow in Kingsnakes

  27. Figure caption for Kingsnakes • a, b, The venomous eastern coral snake (Micrurus fulvius; a) and its non-venomous mimic, the scarlet kingsnake (Lampropeltis triangulum elapsoides; b). c, Geographical distributions of model (yellow) and mimic (yellow, green). For simplicity, sampling locations for genetic analyses are shown for allopatry only (open circles, western allopatry; filled circles, eastern allopatry). d, e, Gene flow among L. t. elapsoides (number of migrants per generation, Nm, shown as means   95% confidence interval) from sympatry into each of two allopatric recipient populations (eastern (d) and western allopatry (e)), as measured in mitochondrial (mtDNA) and nuclear (nucDNA) genomes (the three estimates in each population and genome reflect three runs of MIGRATE-n). Asterisks indicate estimates significantly greater than 0.

  28. Value of genetic diversity • Why are genes valuable? Or • What kind of value do genes have?

  29. Value of genetic diversity • Genes have instrumental value – they are valuable for what they do

  30. Grassy Stunt Virus in Rice

  31. Oryza nivara

  32. Native habitat of O. nivara in Uttara Kannada, India and Distribution

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