100 199 1 100 133 2 100 100 5 100 57 10 100 33
Uneven distribution of progeny
σ2
variance of family size
Nc
census size
σ2 Nc Ne
Ne = 4Nc − 2 σ2 + 2
σ2
random mating = 2(1 − 1/Nc)
Uneven distribution of progeny
Red Drum (redfish)
Family Sciaenidae, DRUMS Sciaenops ocellatus
Description: chin without barbels; copper bronze body, lighter shade in clear waters; one to many spots at base of tail (rarely no spots); mouth horizontal and openng downward; scales large. Similar Fish: black drum, Pogonias cromis. Where found: juveniles are an INSHORE fish, migrating out of the estuaries at about 30 inches (4 years) and joining the spawning population OFFSHORE. Size: one of 27 inches weighs about 8 pounds. *Florida Record: 51 lbs., 8 ozs. Remarks: red drum are an INSHORE species until they attain roughly 30 inches (4 years), then they migrate to join the NEARSHORE population; spawning occurs from August to November in NEARSHORE waters; sudden cold snaps may kill red drum in shallow, INSHORE waters; feeds on crustaceans, fish and mollusks; longevity to 20 years
- r more.
Turner, T. F., J.P. Wares, and J.R. Gold. 2002. Genetic Effective Size is Three Orders of Magnitude lower than Adult Census Size in an Abundant, Estuarine Dependent Marine Fish (Sciaenops ocellatus). Genetics
Ne = 1854 Nc = 3, 400, 000
Genetic drift and mutation balance
With mutations a random mating population of diploids has the chance to acquire 2N new alleles every generation. A population looses variability at a rate of
1 2Ne ∆H = µ − 1 2Ne mutation rate loss rate ∆H = µ − 1 2Ne
Small population loose alleles faster than they arrive in by mutation Small population are not at mutation-drift equilibrium. Heterozygosity H will decrease over time
Small populations
→
Relationship between Heterozygosity and Population size
Red-cockaded woodpecker
Founder effect
Locality Heterozygosity Expected Heterozygosity 8 Selçuk 0.114 0.132 13 Samos 0.097 0.119 14 Ikaria 0.042 0.050
13
When only few individuals from a large population colonize an island (or other isolated habitat), only a small number of alleles will be present in the new population.