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Lec9b_Feb10_Ernest_ConsGen

Lec9b_Feb10_Ernest_ConsGen - CONSERVATION GENETICS Zebra...

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CONSERVATION GENETICS Ecological Genetics ECL242_PHR242 February 10, 2010 Ernest Lec 9b Assigned readings Ch 8 Conservation Genomics by Ouborg 2009 Zebra shark
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CONSERVATION GENETICS SMALL POPULATIONS = GENETICALLY THREATENED Genetic drift Inbreeding Deleterious alleles Genetic load PVA / PHVA Inbreeding depression & outbreeding depression Genetic restoration Management and Conservation Units IUCN categories, ESU and MSU
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CONSERVATION GENETICS INTRODUCTION Passenger Pigeon 1920 Chromolithograph by Hayashi and Toda Evolutionary theory: very small populations face dangers —inbreeding depression — low genetic variation — Leading to fitness decreases (inbreeding depression …that keep them from recovering, despite efforts to preserve them Conservation Genetics: Merging of Fields population genetics, molecular ecology, biology, evolutionary biology, systematics, etc. Several levels to conserve biodiversity Genetics Species diversity Ecosystem diversity
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CONSERVATION GENETICS INTRODUCTION Conservation of genetic variability important to overall health of populations Decreased genetic variability extinctions Molecular techniques utilize individuals’ genetics to assess a population variation Research may suggest steps to fix or reverse the factors that lead to extinction, or reduced biodiversity. Passenger Pigeon 1920 Chromolithograph by Hayashi and Toda
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CONSERVATION GENETICS ROLES FOR MOLECULAR MARKERS Distinctions among Current survival probability Evolutionary potential Neutral genetic variation vs. adaptive/functional/expressed genomic variation (Ouborg etal 2009 paper for today) Emerging pathogens Signals of effects of global climate change Physical changes in landscape habitat
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CONSERVATION GENETICS – ROLES FOR MOLECULAR MARKERS Ne, Effective pop size Gene flow ID Pop bottlenecks recent vs distant past Reln between gen diversity and pop viability Only recently non-invasive sampling practical 10-15 years ago – needed destructive sampling to obtain suffic. sample for allozymes, mtDNA
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N e - effective population size Population size varies over time Suppose there are t non-overlapping generations , then Ne is given by the harmonic mean of the population sizes: Harmonic mean often most appropriate for rates
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N e population size , N N = 10, 100, 50, 80, 20, 500 for six generations ( t = 6). Effective population size is the harmonic mean
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N e population size , N N = 10, 100, 50, 80, 20, 500 for six generations ( t = 6). Then effective population size is the harmonic mean of these, giving: = 0.032 N e = 30.8 Note this is less than the arithmetic mean of the population size, which in this example is 126.7. Of particular concern is the effect of a population bottleneck .
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CONSERVATION GENETICS INBREEDING AND GENETIC LOAD Inbreeding (breeding among relatives) increased homozygosity fixation of mildly delet. Alleles increase genetic load Decline in fitness
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