Butterfly dichromatism primarily evolved via Darwin's, not Wallace's, model

Area of Science:

• Evolutionary Biology
• Ecology and Evolutionary Biology
• Animal Behavior

Background:

• Sexual dimorphism, particularly dichromatism, is often attributed to sexual selection favoring male traits (Darwin).
• Alternatively, natural selection might reduce female expression of elaborate traits (Wallace).
• Previous studies on birds show mixed evidence, while butterfly dichromatism lacks extensive research.

Purpose of the Study:

• To investigate the evolutionary drivers of butterfly coloration and sexual dimorphism.
• To test the relative roles of sexual selection and natural selection in shaping butterfly color patterns.
• To provide a large-scale phylogenetic analysis of European butterfly coloration.

Main Methods:

• A comparative phylogenetic analysis of 369 European non-hesperiid butterfly species.
• Modeling evolutionary color changes for each species and sex along their phylogeny.
• Utilizing phylogenetic ridge regression to estimate evolutionary rates in 3D color space.

Main Results:

• Male butterfly coloration evolved significantly faster than female coloration.
• The rate of male color evolution was particularly pronounced in strongly dichromatic species.
• Males contributed approximately twice as much to changes in dichromatism compared to females.

Conclusions:

• The findings support Darwin's sexual selection model as the primary driver of dichromatism in European butterflies.
• Sexual selection on male coloration appears to be a dominant evolutionary force.
• This study provides robust evidence for the role of sexual selection in butterfly color evolution.