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14 Cards in this Set
- Front
- Back
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When is inbreeding likely to affect population viability?
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● Usually true in small pops
○ Have to have inbreeding ○ Inbreeding depression must occur ○ Traits affected by inbreeding depression must reduce population viability |
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Population viability based on demographic criteria from the IUCN includes probability of persistence over a specified timeframe. What is special about the timeframes?
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–Incorporate short term urgency and long-term concerns
–Considers generation time –PVA: shorter time periods recommended b/c errors in models are propagated in longer time periods |
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What does population viability analysis do?
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•Models to assess whether populations are likely to persist
•Used to identify sppof concern, set priorities, develop recovery plans •Includes chance events (stochasticity) in demography, environment, natural catastrophes, and genetics •Includes synergistic interactions between demographic events and genetic effects |
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Inbreeding depression can reduce reproductive success and survivorship thereby reducing population viability. How else does genetic variation affect population viability?
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1.mtDNA
2.Separate mating types 3.Haplodiploid species 4.mutational meltdown 5.Loss of evolutionary potential |
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inbreeding depression and mtDNA
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•Sperm are powered by mitochondria, reductions in power output reduces male fertility (no effect on females)
•Population viability reduced by mtDNA haplotypes that lower fitness •Ne for mtDNA about 1/4Ne for nuclear genes •More sensitive to drift and bottlenecks |
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inbreeding depression and separate mating types
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–50% of plants have genetic incompatibility mechanisms
–Self-incompatibility locus (S) –Pollen grains can only fertilize plants that do not have the same S allele –Homozygotes cannot be produced at this locus –Smaller populations have fewer S alleles than larger populations –Reducing the number of S alleles reduces the frequency of compatible matings |
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inbreeding depression and Haplodiploid species
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•Sex determined by genotype at one or more loci, commonly one locus with 10-20 alleles
–Ants, bees, wasps, thrips, whitefly & others •At sex determining loci: –Heterozygotes= female –Haploids and homozygous diploid = male •Loss of allelic variation caused by bottlenecks or drift increases homozygosityat sex determining loci and increases the number of males •Diploid males sterile •Fewer females –Reduced foraging productivity –Reduced population size –Skewed sex ratio and reduced Ne |
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inbreeding depression and mutational meltdown
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•Small populations accumulate deleterious mutations b/c natural selection is overpowered by drift
•Population declines in fitness and becomes smaller •Rate that deleterious mutations accumulate accelerates •Feedback process •Could substantially decrease long-term viability over the course of hundreds or thousands of generations |
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inbreeding depression and loss of evolutionary potential
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•Reduces ability to respond to future changes (which will occur eventually)
•Depends on heterozygosity and number of alleles •e.g. Mhcand disease resistance |
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Genetics can be used to estimate census population size using which two methods
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1. Rarefaction
2. Capture-mark-recapture |
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Rarefraction
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•Estimate minimum pop size by counting the number of unique genotypes
•E.g. 30 unique genotypes out of 115 coyote feces samples. Kohn et al. 1999 •Estimate can be corrected to take into account the probability of not sampling individuals |
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Capture-mark-recapture
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•Can be used with genetic data
•Multilocusgenotypes are the permanent marks •Nc= (N1X N2)/R –N1= number of individuals in the first sample –N2= the number of individuals in the second sample –R = number of animals recaptured •10 animals caught in the first sample •10 animals caught in the second sample •5 animals captured in the second sample were “marked” •Nc= (10 X 10)/5 = 20 |
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Estimate the number of males and females in a population of peccaries using genetic mark-recapture data:
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Nc = (N1 X N2)/R
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Issues with genetic markers may cause an underestimation or overestimation of
population size. What are these issues? |
book:
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