Geography Flashcards
cline
a smooth change in a trait over a space
local selection pressure causes
“mosaic local adaptation” - different adaptations in different areas of a location
rate of gene flow impacts…
strength of the trait gradient (cline)
migration
movement of adults
dispersal
movement of gametes ex. seeds in the wind
migration rate in discrete environments
proportion of a generation that came from a separate area
m (migration rate) is always…
between 0 and 1
Δp = m(pm -p)
pm = allele frequency of outside area
p = allele frequency of area in question
Δp = change in allele frequencies
m=0
no change in allele frequencies due to migration
if m «_space;s,
p̂ = m/s
(similar to mutation/selection equation since mutation and migration are 2 sources of genetic diversity)
Fst
quantifies the genetic difference between populations
Fst equation
Fst = variance of p / p̂ (1 - p̂)
Fst for neutral mutations
Fst = 1 / (1 + 16xNe/m)
Ne
effective population size, estimated
effective population size
the size of an idealized population (continuously breeding hermaphrodites) that would experience the same rate of genetic drift as the real population
isolation-by-distance is found through
comparing Fst between many populations that are variable distances apart
different parts of a genome can have
different Fsts, example: stickleback fish - marine individuals end up in freshwater - adaptive process has happened many times and is easy to study as a non-random event
baseline Fst represents
drift vs. gene flow
peak Fst values represent
selection vs. gene flow
why is Fst mapping important?
loci that are outliers for extreme allele frequency differences between populations may be adaptive
why is geographic diversity beneficial
if one population of a dispersed species or a species with a high migration rate goes extinct, species/alleles will still persist
factors to consider when looking at unequal distribution of species
where did they originate/when did they start to migrate/how long did this process take? aka history
ecology - local biotic communities
environment - local abiotic conditions
