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Lecture 15

Lecture 15 Conservation Genetics

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Doug Thomson

Lecture 15 BIO220 Conservation Genetics Biodiversity • #, kinds of organisms in a given area • Interspecific variation/species diversity o Studied by ecologists • Intrapspecific variation/ genetic diversity o Studied by evolutionary geneticists Intraspecific, genetic diversity 1. Within individuals (heterozygosity) 2. Between individuals in same population 3. between populations of the same species Conservation genetics o apply genetic methods to conservation, restoration, endangered species management o Different solutions address loss of genetic diversity at each of 3 levels Genetically declining populations o Genetic drift enhanced o Increased chance changes in gene frequency o Decreased genetic variation (alleles fix randomly) o Inbreeding more common o Decreased heterozygosity o Increased inbreeding depression from exposure of rare, recessive alleles o Kiss if heterozygote advantage (hybrid vigor) for fitness Demographic effects of declining populations o Potential for allele effects enhanced o reproductive rate depends positively on density o decreased densities, decreased reproductive rate o likely in colonial breeders o Increased risk: demographic stochasticity o Random differences among individuals in survivorship, reproduction  variation in population growth rate o Happens even if individuals have same average survival and reproduction o Most important in small populations o Genetics o The influence of population decline on N aed its consequences should predominate in leading to extinction o Demography o The effects of demographic stochasticity should predominate and lead to extinction before the effects of genetics can manifest o Importance of alternative world views: alternative management actions for rare, endangered, declining species. Case: Cheetahs • Genetically depauperate • Low polymorphic loci in population • Low heterozygosity in individuals • MHC locus o Lacks variation o Captive cheetahs do not reject skin grafts from others • In captive cheetahs o Decreased sperm count o High disease load Early View • Historical bottleneck, Decreased Ne • Inbreeding during decreased N/N eurther reduced N.N e • Disease, MHC symptoms,  interactive effect of loss of genetic diversity and threats to population persistence The complications • Wild population cheetahs no signs of disease, increased viral load, infectious disease induced mortality • Most mortality of cubs due to predation o Decreased genetic variation is u
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