A population of plants varies in flower size, having a normal distribution with

Question

A population of plants varies in flower size, having a normal distribution with a mean of 30mm and a standard deviation of 2mm. Suppose that flowers less than 28mm are avoided by pollinators whereas plants greater than 32mm are so large that pollinators visit but do not touch the stamens/stigma resulting in a lack of pollination and therefore no fruit set. What kind of selection is acting on flower size?

a.) Balancing selection

b.) Disruptive selection

c.) Directional selection

d.) Genetic drift

e.) Stabilizing selection

Explanation / Answer

Ans E

Stabilising selection is acting on flower size. Here the population diversity decreases, and the population mean stabilises over a particular trait value which is 28 to 32 mm in this case.

It favours the average individuals over the extreme ones.

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