What is the Difference Between Directional and Disruptive Selection?

Directional and disruptive selection are two types of natural selection that can occur in a population. They differ in the way they affect the distribution of traits within a population and the genetic variance.

Directional selection:

Occurs when one extreme of the trait distribution is favored, causing the population's trait distribution to shift toward that extreme.
A single phenotype is favored, and the allele frequency continuously shifts in one direction.
Decreases genetic variance in a population.

Disruptive selection (also known as diversifying selection):

Occurs when extreme values for a trait are favored over intermediate phenotypes.
Both extreme phenotypes have higher fitness than intermediate phenotypes, causing the population's trait distribution to develop two peaks.
Increases genetic variance in a population.

In summary, directional selection favors one extreme of a trait distribution and shifts the population's trait distribution in that direction, while disruptive selection favors both extreme phenotypes and results in a population with two peaks in its trait distribution. Directional selection decreases genetic variance, while disruptive selection increases it.

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What is the Difference Between Directional and Disruptive Selection?

Comparative Table: Directional vs Disruptive Selection

Directional and disruptive (or diversifying) selection are two types of natural selection that differ based on the traits they favor and the impact on genetic variance. Here is a table comparing the two:

Aspect	Directional Selection	Disruptive Selection
Number of traits favored	One extreme trait is favored.	Both extreme traits are favored.
Allele frequency shift	Causes the allele frequency to continuously shift in one direction.	Results in two overlapping phenotypes, one at each extreme.
Genetic variance	Can decrease variation in the entire population.	Can reduce variation only in some individuals.
Examples	- The evolution of the peppered moth, where dark-colored moths were favored due to increased industrial soot. - The evolution of the giraffe neck, where long-necked giraffes were favored for reaching more leaves.	- A population of mice living at the beach, where light-colored mice blending in with the sand and dark-colored mice hiding in the grass are favored at both ends of the spectrum. - Plant height and their respective pollinators, where extreme heights are selected for separate pollinators, resulting in a two-peaked curve.

In summary, directional selection favors one extreme trait, causing the allele frequency to shift in one direction and potentially decreasing genetic variance in the entire population. On the other hand, disruptive selection favors both extreme traits, resulting in two overlapping phenotypes with reduced variation in some individuals but not necessarily in the entire population.

Guilherme Mazui

Guilherme Mazui is graduated in journalism from the Federal University of Minas Gerais (UFMG) and a master's degree in Communication from the University of São Paulo (USP). In addition, he has experience in advertising writing and has worked as a content editor in several companies.