Rnr 4103 Conservation Genetics: Lect 12 Population Subdivision

Front 1

FIT

Back 1

Departure from HW in the entire population as a result of non-random mating within a subpopulation (Fis) and genetic differentiation among populations (Fst): inbreeding of individuals (I) in the total population (T)

Front 2

FIS

Back 2

Departure from HW within a subpopulation: inbreeding of individuals (I) relative to their subpopulation (S)

Front 3

FST

Back 3

Genetic differentiation (allele frequency divergence) among populations: inbreeding due to differentiation among sub-populations (S) relative to the total population (T)

Front 4

Positive FIS values

Back 4

a deficit of heterozygotes
population is inbred

Front 5

High FIS values

Back 5

due to clustering of relatives
-offspring established close to relatives
-clumping of individuals from bird and rodent seed caches

Front 6

Calculate FST

Back 6

FST = 1 – (HS/HT)

Front 7

limitations of FST

Back 7

○ If variation within subpopulations is high, FST is biased downwards
○ If HS= 0.9 then FST cannot be higher than ~0.1
○ Does not consider identity of alleles
○ When variation within subpopulations is high, the proportion of total variation distributed between populations has to be low
○ Can get low FSTvalues even if two populations share no alleles
○ Use RST or φST instead (uses info on identity/length of alleles)

Front 8

How does gene flow affect variation within and among populations

Back 8

● Low gene flow can lead to inbreeding depression
● High gene flow can limit local adaptation
● Reintroducing gene flow can result in genetic rescue
○ Can help predict likelihood of recolonization o f vacant habitats

Front 9

2 ways to measure gene flow with molecular methods

Back 9

○ Indirect measures of average migration rates (Nm)
○ Direct estimates of dispersal rates