Opsin expression predicts male nuptial color in threespine stickleback

Area of Science:

• Evolutionary Biology
• Animal Behavior
• Genetics

Background:

• Sexual selection models propose that male signals evolve via genetic correlations with female preference.
• When female preference involves signal sensitivity, correlations between male signals and perception are expected.
• In species where signals are male-limited, these signal-sensitivity correlations should be found in males.

Purpose of the Study:

• To investigate the presence of signal-sensitivity correlations in male threespine sticklebacks.
• To explore the role of opsin expression in mediating these correlations.
• To understand the implications for sexual selection and the maintenance of color variation.

Main Methods:

• Documented correlations between nuptial coloration and opsin expression in a breeding population of threespine sticklebacks.
• Assessed the relationship between male coloration (redness) and the expression of long-wavelength-sensitive (LWS) opsin.
• Controlled for potential confounding factors such as optical microhabitat tuning.

Main Results:

• Found a significant correlation between redder male nuptial coloration and increased LWS opsin expression.
• Males with redder coloration exhibited greater sensitivity to orange and red wavelengths.
• This correlation was independent of shared tuning to the underwater light environment.

Conclusions:

• Opsin expression variation provides a substrate for the evolution of signal-preference links in sexual selection.
• The identified correlation highlights a potential sensory mechanism driving negative frequency-dependent selection.
• This mechanism can contribute to the maintenance of male nuptial color diversity through male-male competition.