Final Exam Study Guide Flashcards
negative density dependence
- can help pull a population towards an equilibrium size range
- is stabilizing
causes of negative density dependence
- intraspecific competition
- disease
- predation
carrying capacity
- also known as K
- when population is at K, r is approximately 0
- it is a range, not a single range
positive density dependence
- occurs when vital rates and/or population growth rate increase as density increases
- destabilizing
at low numbers, positive density dependence is called…
the Allee effect
Allee effect
arise via small-population breakdowns in mating behaviors or the ability to find mates
biological mechanisms of the Allee effect
many of the famous Allee effects arise via small-population breakdowns in mating behaviors or the ability to find mates, or in the ability to collectively make necessary habitat modification or engage in successful cooperative feeding
biological mechanisms of the Allee effect : mating and caring for young
- mate limitation
- cooperative breeding
biological mechanisms of the Allee effect : foraging advantages
- detection and access to food
- cooperative feeding
biological mechanisms of the Allee effect : predator-method
- predator detection/confusion/defense
- others driven by how predation changes with prey numbers
genetic variation
the difference in the genetic makeup (DNA) of individuals or populations among the same species
why is genetic variation improtant?
important for survival and adaptation of a species as it helps in terms of natural selection and evolution
effective population size (Ne)
the number of individuals that effectively participates in producing the next generation
which is smaller, census size or effective size of a population?
effective size of a population
small Ne
bigger increase in genetic drift
when is Ne highest?
at equal breeding sex ratio
genetic drift
change in allele frequencies by chance
what does genetic drift cause?
a loss of genetic diversity
where is genetic drift most common?
in small populations
what does a population bottle neck lead to?
genetic drift
when does genetic drift occur?
occurs when an event drastically reduces population size
how to measure genetic drift?
- depends on Ne
- essentially the number of individuals in a population who contribute offspring to the next generation
gene flow
the movement of alleles between populations
when does gene flow occur?
occurs when individuals join new populations and reproduce
gene flow keeps…
keeps neighboring populations similiar
low gene flow
increases the chance that two populations will evolve into different species
inbreeding
loss of heterozygosity and increased expression of recessive homozygotes
F IS
inbreeding due to preferential mating with relatives
F ST
- inbreeding due to genetic drift in a small population mating randomly
- a measure of loss of heterozygosity
loss of heterozygosity =
increase in homozygosity
F ST range
0-1
F ST range = 0
no loss of heterozygosity
F ST range = 1
complete loss of heterozygosity
inbreeding depression
the loss of heterozygosity and expression of deleterious recessive alleles due to inbreeding disturbs vital rates
example of inbreeding depression
- births
- deaths
migration
movement of large numbers of one species from one place to another, often round trip
dispersal
permanent movement away from population of origin to another population
immigration
dispersal into a target population
emigration
dispersal out of a target population
one-migrant-per-generation (OMPG) rule
- typically maintains genetic diversity
- balances local adaptation
- independent of population size
- migrant has to have the same probability of breeding
how to measure connectivity/dispersal
- mark mark-recapture methods
- radio telemetry
- VHF & acoustic telemetry
- satallite transmitters
- genetic assignment test
how to measure connectivity/dispersal: mark mark-recapture methods
- great for tightly colonial species
- great for heavily harvested species
- need to know where to look for dispersing animals
how to measure connectivity/dispersal: radio telemetry
- mark animals with a radio transmitter
- follow them
different types of radio telemetry
- VHF
- acoustic
- satellite
how to measure connectivity/dispersal: VHF & acoustic telemetry
- easier to find dispersers than CMR
- limited by range of the transmitter
VHF & acoustic telemetry: limited by range
- which is limited by its size
- aircraft and now drones can help search
- freshwater & marine applications
how to measure connectivity/dispersal: satellite transmitters
- mark animals with transmitters
- sit at your desk and let a satellite track them
- good for broad scale movement but not always extremely accurate
- expensive and relatively heavy
how to measure connectivity/dispersal: genetic methods - assignment test
designed to directly detect individuals that disperse from their population of birth
metapopulations
population of populations
habitat occurs in ________ patches
discrete
dispersal occurs ________ patches
between
are all patches created equal?
no
source population
serve as a net contributor to the metapopulation
sink population
population that drains the metapopulation
ecological/evolutionary traps
- human created sink habitats
- preferentially chosen over better habitats but far less suitable
corridors
- help restore connectivity
- positive effects on BIDE components
- bridge for Christmas Island Red Crabs
- Trans-Canada Highway in Banff National Park
translocation/reintroduction
- help restore connectivity
- human mediated physical translocation of animals may be required to avoid extinction
- demographic rescue
- population augmentation
- reintroduction
five categories of anthropogenic stressors
- conversion of land and sea
- overexploitation through harvest
- invasive species
- pollution
- climate change
three main types of responses to stressors
- move to a more appropriate abiotic environment
- locally adjust in place
- head towards extinction as vital rates decrease
distribution shifts
- move
- adjust
- decrease
distribution shifts: move
climate change-induced movements: poleward and/or higher in elevation
distribution shifts: adjust
when faced with a tough challenge a species can deal with it aka adjust
phenotypic plasticity
- ability of individuals to change in response to their environment
- occurs within an individuals lifetime
evolution
- changes in genes over generations, facilitated by natural selection
- can occur fairly quickly
connectivity
connectivity among populations may be as important as dynamics within component subpopulations
Nt+1 = Nt + B + I - D -E
connectivity equation
why is connectivity important?
- persistence and fluctuation of populations
- rescue effects
- synchrony
colonization of new sites
permits response to changing environmental conditions
recolonization
increase persistence of suite of populations
genetic rescue OMPG rule
- at least one migrant individual. per generation is necessary to prevent significant divergence in allele frequencies among subpopulations
- minimize the loss of heterozygosity that could lead to inbreeding depression allowing the local adaptation among subpopulations
what caused the reduction in genetic diversity?
- predation
- habitat destruction
- hunting
- inbreeding
goal of genetic rescue
- introducing genetically diverse individuals into small, isolated populations with low genetic diversity
- to restore species to full genetic health so they can thrive in the wild without further intervention
genetic rescue aims to…
increase genetic diversity and minimize inbreeding to enhance the fitness and adaptability of populations
how does genetic rescue occur?
- occurs naturally
- also facilitated to safeguard at-risk populations and enhance their ability to adapt to environmental changes
genetic rescue
to increase a populations fitness by introducing new genetic variation
species characteristics of higher extinction risk
- lower abundance
- restricted range/endemism
- higher speciation
- larger body size
- longer generation time
- shorter dispersal rate
- higher human need
3 stochastic factors that small populations are vulnerable to
- demographic
- environmental
- genetic
demographic stochasticity
mean vital rates are probabilistic
environmental stochasticity
drives random changes in vital rates
genetic stochasticity
- arises from genetic drift
- can lead to inbreeding depression)
extinction vortex
- human-caused deterministic stressors & stochastic stressors interact
- make small populations smaller, eventually leading to their collapse
The Minimum Viable Population (MVP) Concept
- 50-500 rule, expressed in terms of the effective population size
- not the best method
MVP concept: short term
Ne ≥ 50 to minimize short-term loss of fitness due to inbreeding
MVP concept: long term
Ne ≥ 500 to ensure long-term maintenance of genetic variation/preservation of evolutionary potential
