We want to determine whether time to sexual maturity egg lay

We want to determine whether time to sexual maturity (egg laying) in Nile crocodiles is a heritable trait. Sexual maturity in crocodiles is determined by body length (males after passing the 10-foot mark and females after passing the 7-foot mark). A population of 100 crocodiles takes an average time of 4, 380 days (12 years) to reach sexual maturity. We select ten crocodiles that reached maturity earliest; their average time to adulthood is 3, 301 days. We breed those 10 early-adult crocodiles with each other and monitor the resulting offspring. We watch to see when they mature; the average time to maturity is 3, 875 days. Calculate the selection differential. Calculate the response to selection. Calculate heritability (h^2). Interpret the heritability of maturity in crocodiles from above.

Solution

Selection differential

Selected parents average maturity = 3301 days

Average crocodile maturity is given = 3875 days

S = Ts – T, where Ts is mean of selected parents and T is mean of population

S= 3301 – 4380 = -1079 days                         [offspring have 1079 less days than the normal maturity days]

Response to selection

R = To –T where To is mean of offspring of selected parents

To = Ta – S = 3875 -1079 = 2796 days          [Ta = average time to maturity]

So R = 2796-4380 = -1584 days

Heritability h² = R/S = 1584/ 1079 = 1.468

h= 1.468 = 1.21

Heritability of maturity would be consider for two maturities, normal and population

Again h² = 3875/ 4380 = 0.884

h= 0.884= 0.94