204Z references Flashcards
genetics and extinction: introduction
-Richard Frankham
- In small populations, inbreeding and loss of genetic diversity is unavoidable
-Less individuals to mate with and so gene pool gets smaller and smaller
genetics and extinction: inbreeding depression
-Richard Frankham
-Effects both wild and captive populations
-Purging of deleterious alleles doesn’t always have great effect in small populations
-Deleterious alleles begin to become ‘neutral’ or ‘fixed’ so harder to be purged
-Small, inbred populations can be recovered by outcrossing
genetics and extinction: loss of genetic diversity
-Richard Frankham
-has a long term impact on extinction risk
-genetic diversity is raw material on which adaptation can occur, loss of this will lead to increased risk of extinction
genetics and extinction: mutation accumulation and meltdown
-Richard Frankham
-Small populations: drift more powerful than selection
- deleterious alleles increase in frequency
challenges and opportunities of genetic approaches to biological conservation: Genetic management of captive populations
-Richard Frankham
-maintain genetic diversity, minimise inbreeding
-prevent genetic adaptation to captivity as this can have a deleterious effect on wild fitness
challenges and opportunities of genetic approaches to biological conservation: conservation genomics
-Richard Frankham
-Sequencing whole genomes
-Provides basic information on genetic
diversity of species
-Allows development of genetic markers
-estimate Ne, demographic history, levels of inbreeding, rates of gene flow, differentiation among populations and taxonomic status.
challenges and opportunities of genetic approaches to biological conservation: integrating genetics into conservation biology
-Richard Frankham
-Inbreeding explained 26% of extinction risk in in Glanville fritillary butterfly in Finland
The alluring simplicity and complex reality of genetic rescue
-tallmon, luikart and waples
-small amount of immigrants in a population can have immediate positive effect on fitness
-important in helping small, fragmented populations survive
The alluring simplicity and complex reality of genetic rescue : Fitness effects of immigrant genes
-tallmon, luikart and waples
-First generation of offspring from migrants and local individuals have increase in heterozygosity, but it is common for this to decline in future generations
Extinction vortex (introduction to conservation genetics)
-describe the processes that declining populations undergo
Declining population paradigm (Directions in conservation biology)
-Causes that make populations small in the first place
-Two areas of theory on declining population paradigm:
o Causes of extinction
o How agents of decline might be identified
-The evil quartet
Overkill
Habitat destruction and fragmentation
Impact of introduced species
Chains of extinction
Small population paradigm (Directions in conservation biology)
-Risk of extinction due to low numbers
Inbreeding coefficient F
-Probability that two alleles at any given locus on an individual’s chromosome are identical by descent
estimating inbreeding coefficient
-in zoos via breeding registers
-fingerprinting
Hardy Weinberg model (HW)
-Calculate genotype frequencies based on allele frequencies
-Theoretical predictions of allele and genotype in the environment
How does a population conform to hardy Weinberg principle?
1) Mendelian segregation occurs
2) Random mating (panmixia)
3) No mutation
4) Large population (no drift)
5) No selection
6) No migration
Why is increasing homozygosity a problem for populations?
-Leads to dominance and overdominance
-The expression of these two effects leads to an increased genetic load
FST
-Used to detect structuring in population
-Panmixia population: high levels of gene flow, mixture of individuals in the population
-Sub-structuring population: no gene flow between them
IBD (isolation by distance)
-In many species, as populations become further apart, gene flow becomes lower
-Organisms that are less mobile or disperse further have steeper slopes, as when you get to about 2,000 Km, those populations have no gene flow
How we measure population growth
-Using r or lambda
Four main vital rates affecting population growth
- Birth rate
- Death rate
- Emigration
- Immigration
r
b-d (population growth = births-deaths)
lambda
Nt+1/Nt
(next generation divided by first generation)
Abundance
population size now
oAbundance = count
Probability of detection
Fecundity
average number of offspring per individual of a given age in a given step
Recruitment
net population production after births and deaths accounted for
equation that links r and lambda
r=ln(λ)(lambda)(Nt+1/Nt)
4 studies used and dates
-genetics and extinction (2005)
-challenges and opportunities of genetic approaches to biological conservation (2010)
-The alluring simplicity and complex reality of genetic rescue (2004)
-Directions in Conservation Biology: Graeme Caughley (1994)
The evil quartet
-Overkill
-Habitat destruction and fragmentation
-Impact of introduced species
-Chains of extinction
Overkill
Hunting at a rate above the maximum sustained yield
Habitat destruction and fragmentation
Degradation of habitat due to grazing, draining of wetland, cutting down forest.
Impact of introduced species
Extermination of native species due to introduction of alien (invasive) species
Chains of extinction
Extinction of one species as a result of extinction of another species
agents of decline identification
study the natural history of the species to gain knowledge of its ecology, context and status
Small population paradigm factors
-Demographic stochasticity
-Environmental stochasticity
-Inbreeding
-Inbreeding depression
-Metapopulations
-Minimum viable population
-Population viability analysis
Declining population paradigm factors
-Minimum viable population
-Population viability analysis
Ne equation
475/L
-L = generation time
ESU
-evolutionary significant units
-populations with separate management for conservation due to high distinctiveness
pre-zygotic isolation
occurs before the formation of a zygote
post-zygotic isolation
occurs after zygote produced by mating
hybridisation
occurs when humans introduce exotic species into range of rare species or alter habitat so that previously isolated species are in secondary contact
metapopulation
population of population
-one big population with loads of subpopulations
metapopulation theory
-Habitat loss effects metapopulation structure as it decreases amount of connectivity between patches
-When extinction rate exceeds colonisation rate reduction in number of patches occupied in habitat occurs
marine metapopulation example
-marine isopod: idotea metalica
-lives on surface drifting patches of debris that float around on the open sea
How large does Ne need to be for populations to be viable?
475 individuals
Extinction vortex diagram
- Habitat loss
- Pollution
- Over-exploitation
- Exotic species
arithmetic mean
add all values, divide by how many
geometric mean
multiply all values, root by how many values there are
negative density dependence
death rate exceeds birth rate at large population sizes
