A male spider's ornamentation polymorphism maintained by opposing selection with two niches

Area of Science:

• Evolutionary Biology
• Population Genetics
• Ecology

Background:

• The Levene mechanism, proposed 60 years ago, explains how genetic polymorphism can be maintained by opposing selection across different environments.
• However, finding natural systems that meet its strict conditions has been challenging.

Purpose of the Study:

• To identify and report a natural system that exemplifies the Levene mechanism.
• To investigate the genetic polymorphism in a wolf spider population inhabiting a mixed-substrate environment.

Main Methods:

• Observed a wolf spider population in a habitat of mixed rocks and leafy litter.
• Developed and applied a Levene-type population genetics model to census data.
• Analyzed male phenotypes subject to opposing selection based on substrate.

Main Results:

• The wolf spider population exhibited distinct male phenotypes adapted to different substrates (rocks vs. leafy litter).
• Census data best-fitted a Levene-type population genetics model, supporting the maintenance of genetic polymorphism.
• Model parameters were quantitatively consistent with laboratory studies on related species.

Conclusions:

• This wolf spider population provides a rare empirical example of the Levene mechanism in action.
• The findings demonstrate how opposing selection in heterogeneous environments can maintain genotypic diversity.
• The study validates the applicability of the Levene mechanism to natural populations.