This is because sexual ornaments are under intense directional selection.

Directional selection always favours those with higher rates of fecundity within a certain population.

If such a niche is already occupied, competitive pressure may oppose the directional selection.

Directional selection, a particular mode or mechanism of natural selection.

Nevertheless, most natural populations, at most times, change much more slowly than they would if subjected to strong directional selection.

It is directional selection that is illustrated in the antibiotic resistance example above.

"Directional selection is the primary cause of phenotypic diversification".

Female selection should lead to directional selection, which would result in a greater prevalence for that trait.

Directional selection occurs when a certain allele has a greater fitness than others, resulting in an increase of its frequency.

Under directional selection on , the loci underlying and may lose all genetic variance.

Directional selection occurs most often under environmental changes and when populations migrate to new areas with different environmental pressures.

The first is directional selection, which is a shift in the average value of a trait over time - for example, organisms slowly getting taller.

For example, let us take the mathematically straightforward yet biologically improbable case of the rabbits: Suppose directional selection were taking place.

A major challenge is to distinguish patterns of local adaptation caused by reciprocal coevolutionary change versus directional selection to any other environmental factor.

In contrast, a more balanced phylogeny may occur when a virus is not subject to strong immune selection or other source of directional selection.

Selective sweeps are one form of directional selection, where the increase in frequency will eventually lead to the fixation of the advantageous allele.

In fact, directional selection leading to functional diversification between orthologs is the least common form of natural selection observed at the molecular level [ 3].

The hypothesis only defines condition as a quantity that correlates tightly with overall fitness, such that directional selection will always increase average condition over time.

Directional selection has led plants to display increasingly diverse amounts of color variations extending into the ultraviolet color scale, thus attracting higher levels of pollinators.

Alternatively, the values of the behavioural traits are not maximized by directional selection, but rather are under the influence of stabilizing selection.

These include sexual selection, ecological selection, stabilizing selection, disruptive selection and directional selection (more on these below).

The forces of natural selection have continued to operate on human populations, with evidence that certain regions of the genome display directional selection in the past 15,000 years.

With directional selection, the allele frequencies will tend towards an equilibrium position with the fittest allele reaching a frequency in mutation-selection balance.

One resolution to the lek paradox involves female preferences and how preference alone will not cause a drastic enough directional selection to diminish the genetic variance in fitness.

The effect of directional selection on the shape of a viral phylogeny is exemplified by contrasting the trees of influenza virus and HIV's surface proteins.