29. Hybridization and Genetic Extinction

29. Hybridization and Genetic Extinction - Hybridization...

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Hybridization and “Genetic” Extinction Can and do we preserve the genetic integrity of species, and if so, how?
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Hybridization Hybridization : mating between different species or two genetically distinct populations that produces offspring, regardless of fertility of offspring
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Golden- and Blue-Winged Warblers Golden winged- warbler Blue winged- warbler Hybrid (Brewster’s Warbler)
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Golden- and Blue-Winged Warblers
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Introgression Introgression : the incorporation of genes from one population or species to another through hybridization that results in fertile offspring that further hybridize with parental populations or species ( “backcross” ) Over several generations, introgression can result in a complex mixture of parental genes, while in simple hybridization 50% of genes will come from each of the two parental species. Without introgression, the parental species or populations are not “contaminated” by hybridization
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Levels of Hybridization Population or Species A Population or Species B F 1 Hybrid (1 st generation) F 2 Hybrid Backcross Backcross (2 nd generation) Introgression
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Hybrid Zones How are hybrid zones maintained? Hybrids may be less fit than parental taxa and selected against, but dispersal into the zone maintains a narrow band of F 1 ’s Hybrids may be more fit than parental taxa in habitats that are intermediate to parental taxas ’ native habitat Species A Species B Hybrid Zone Hybrid zones are often observed in nature…
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Human-caused habitat changes have resulted in distribution changes and expansions for many species Species and genetically distinct populations that were formerly geographically isolated are more likely to come into contact and breed The frequency of hybridization has increased dramatically, posing unique practical and philosophical problems for managers Hybridization and Conservation
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Spotted Owl Barred Owl Hybridization
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“Sparred” Owl Hybrids Sparred Owls Barred Owls Spotted Owls
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Hybridization and Species Diversity Two competing perspectives about the relationship
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29. Hybridization and Genetic Extinction - Hybridization...

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