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Ecological Effects of Roads Connectivity Issues
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An emerging focus for ecologists Island Press 2003
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About 1/5 th of the U.S. land area is thought to be impacted in some way by the public road network. (Forman, 2000 Cons. Biol 14(1):31-35)
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Primary Road Impacts Vegetation Structure and composition Invasive species and pathogens Wildlife Mortality Habitat Connectivity Aquatic Hydrology Sediment Contaminants
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Road effects on Wildlife Mortality Habitat Connectivity
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Efforts to reduce wildlife mortality Forman et al. 2003
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Wildlife Underpasses Banff National Park along the Trans Canada HighwayForman et al. 2003
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Wildlife Overpasses Barcelona, Spain Forman et al. 2003
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Structures for facilitating movement
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Time lags in detecting cumulative road impacts on wildlife
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Genetic approach to the analysis of connectivity Analyze allele frequencies from individuals collected across the landscape Identify “clusters” (populations) of individuals with similar multilocus genotype Most techniques operate by minimizing Hardy- Weinberg and linkage disequilibria Assignment of individuals to populations done on probabilistic basis Use of Bayesian statistics
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Hardy Weinberg Hardy Weinberg principle states that in a population mating at random in the absence of evolutionary forces, allele frequencies will remain constant and the relative abundance of each genotype will be defined by: (p+q) 2 = p 2 +2pq+q 2
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Conditions Necessary To Maintain Constant Allele Frequencies: Random Mating No Mutations Large population Size (no genetic drift) No Immigration Equitable Fitness Between All Genotypes. Departure from H-W equilibrium is an indication that one of the above does not hold
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A southern California freeway is a physical and social barrier to gene flow in carnivores Riley et al. 2006. Molecular Ecology 15:1733-1741
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Bobcat Coyote Genetic Populations Home Ranges Radio tel. locations
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