Flashcards in G21-22 Deck (43):
what % of living species will be extinct by 2050 factoring in climate change and other human activities
give 2 examples of climate change effected species
harlequin frog 67% extinct due to fungal infections due to rising temps
temperature affecting coral reefs inducing bleeching
give an example of extinction due to move up of species up a mountain leaving some no where to go?
45% extinction of endemic forest moth species by 2100, , due to contraction of high and low elevation boundaries on mount kinabalu in bornea.
what does habitat loss lead to
habitat fragmentation - more edge at any point
each fragment more isolated from others leads to population fragmentation and reduced population size
what is bad about having more edge in habitat fragmentation
different microclimate, more problems with competitors at edge and more chance of immigration
assumptions of hwe
= non overlapping generations
- no mutation
- no migration
- no selection
- random mating
- cnst pop size through time
- equal sex ratio.
- equal opportunity to pass on genes
what is genetic stochasticty
Genetic stochasticity refers to changes in the genetic composition of a population unrelated to systematic forces (selection, inbreeding, or migration), i.e., genetic drift
what is demographic stochasticity
Demographic stochasticity refers to the variability in population growth rates arising from random differences among individuals in survival and reproduction within a season.
- random fluctuations in birth and death rates
immigration.emigration sex ratio. age and structure of pop
how do you calcualte propotion of polymorphic loci
no. of polymorphic loci/total no of loci sampled
if 3/6 loci are polymorphic what are the other 3?
how do you calcualte allelic richness
total no of alleles over all loci (poly and mono(1))/ total no of loci sampled
eg. 5 +4+ 3+ 1+ 1+ 1 / 6
what is the observed heterozygosity
total no of heterozygotes at locus/ total no of individuals samples
what is the expected heterozygosity
= 1-p^2 -q^2
what is the effective number of alleles
number of alleles that if equally frequent would give the expected heterozygosity HE
how do you caclulate effective no. of alleles
ne = 1/ the sum of (pi)
pi = frequency of allele squared
what is the theory for how genetic diversity is lost?
random genetic drift ultimately leads to fixation of one alele copy
- leads to homozygosity and IBD - one copy of that allele will win out and alleles will all become identical by descent
what is the allelic richness and heterozygosity found to be in threatened species comparable to non threatened
give an example of each
lower for threatentd
human A =8.9 and H =0.82
whereas the cheetah A =3.4 and H =0.39
what can the degree of inbreeding be related to?
future of expected heterozygosity.
estimated for neutral genes and assumes constant N
what is heterozygosity at any time t equal to
initial hetero after a certain no. generations (inbreeding coefficient)
rate of inbreeding losing 1/2N at each generation
Ht/H0 = (1-1/2N)^t
Ht = (1-1/2N)H0
H0 = heterozygosity observed at time 0 (before bottleneck)
what effect does single generation bottleneck have?
retains 7% of the heterozygosity - long term
what is the calcuculation for the inbreeding coefficient delta
delta = 1 -(fittness of inbred offspring/fittness of outbred offsping)
what is a mutational meltdown?
accumualtion of harmful mutations in a small population
- drift fixes mildly deleterious alleles in small pop, leads to increasing genetic load.
what is genetic load?
reduction in mean fitness of a population compared to that of the max fittness
what is the effective population size
size of idealised population that would lose genetic diversity at the same rate as our actual population
why is an effective pop size needed
because breeding pop could be much smaller than census size, meaning the pop would experience greater rate of drift and loss of heterozygosity.
what would the effective population size be if the population lost genetic diveristy at the same rate of the ideal population
effective population = ideal
what is an idealised popualtion
one that can be be described using a number of assumptions (hwe wright fisher)
why is Ne the effective pop size usually lower than N
due to size variation between generations, unequal sex ratio and sexual selection
what is the min population size required to maintain evolutationary potential
what is the minimm population size required to retain reproductive fittness?
what is the minimum population size required to avoid accumulating deleterious mutations
what is the equation for effective population size taking into account sexual selection and variance between success rates of the sexes
Ne = 8(Nm+Nf)/Vm +Vf +4
Vm = variance in male success
Vf = variance in female success
what is the effective popualtiion size taking into account unequal sex ratio
Ne = 4(Nm x Nf)/ Nm + Nf
what is the allee effect
postivie effect between individual fittness and increasing pop size
give 3 examples of allee effect at low pop size
reduced defence efficiency in lapwings in low pop
reduce foraging efficieny in african wild dogs in low pop
reduced chance of mate location in grizzly bears that have a very large habitat range.
what is population viability analysis
Population viability analysis (PVA) is a species-specific method of risk assessment frequently used in conservation biology. It is traditionally defined as the process that determines the probability that a population will go extinct within a given number of years.
what inputs does pva use
life history data - birth rate, survial rate, reprod rate, habitat capacity etc and stochastic events.
what are the problems with pva
limited knowledge of some species
often doesnt take climate change into account
not that much genetic info
inbreeding depression is often put in for juvenile survivorship not adult breeding
describe the case study of the pva of the ethiopian wolf
- icun endangered species
fragmentation range in highlands
out breaks of disease like rabies
competes with wild dogs for food
sanetti = pure populations web = hybrid with dogs
found hybridisation - outbreeding is the problem
describe the case study of pva with the florida panther
widespread until european settlements
hunting road kill reduced pop to small area so there were only 25 left in 1998
all have low hetero relative to pops elsewhere
nearly fixed deleterious traits inlcuding: kinked tail, undescended testicles, poor semen quality, cowlick on back, lowest molecular vairation of any north american pop
genetically restored by outbreeding with female texan cougar, subspecies was successful
increase in fittness adn higher degree of escape behaviour and increased survivorship of offspring
genetic restoration alone is not enough, requires habitat etc
describe the case study of pva of the mountain ibex
population crash in the 19th centuary
supplemented with austrian ibex
then restored with turkish and nubian ibex
didnt work as went extinct because mountain ibex mate in midwinter so young are born in summer so have time to get big before winter
however nubian and turkish amte in the summer
loss of local adaptation
describe the case study of the dusky seaside sparrow
mosquito and malaria issues meant florida governemnt filled in marshes - where sparrows breed
final few captive males were mated with peninsula females
final male died they looked at its mtDNA and found that the peninsulae birds are completely distinct, most geographically near but different species.