A new test for detecting ongoing selection

Area of Science:

• Evolutionary Biology
• Population Genetics
• Molecular Biology

Background:

• Detecting ongoing natural selection in natural populations is challenging due to its rarity and limitations of existing methods.
• Past selection signatures in DNA are well-studied, but current selection is less understood.
• Viability selection, acting over a single generation, is a key evolutionary process that remains difficult to detect.

Purpose of the Study:

• To develop and validate a new statistical test for detecting viability selection acting within a single generation.
• To compare measures of genetic variation between specific chromosomal groups to infer selection.
• To apply the new test to a natural population to assess its effectiveness.

Main Methods:

• A novel test was designed comparing variation measures in 'focal' chromosomes from heterozygous and homozygous individuals.
• Reference chromosomes were used to define 'focal' chromosomes, allowing for direct comparison.
• The test was applied to In(2L)t inversion polymorphism data in a Drosophila melanogaster population, using standard chromosomes as the focal class.

Main Results:

• The new test detected significant differences in allele frequency and haplotype number between the two groups of standard chromosomes.
• These differences suggest the presence of currently acting selection, despite no deviation from Hardy-Weinberg equilibrium.
• The findings indicate the sensitivity of the new test in identifying selection pressures.

Conclusions:

• The developed test offers a powerful new approach to detect ongoing viability selection in natural populations.
• Combined with Hardy-Weinberg equilibrium tests, this method can provide insights into the frequency of strong selection.
• This research advances our ability to study contemporary evolutionary processes in real-time.