Speciation is associated with changing ornamentation rather than stronger sexual selection

Area of Science:

• Evolutionary Biology
• Ornithology
• Speciation Research

Background:

• Sexual ornamentation is known to mediate reproductive isolation between species.
• Previous research suggested stronger sexual selection promotes speciation, but evidence is lacking.
• The role of decreased ornamentation in speciation has been overlooked.

Purpose of the Study:

• To investigate whether changes in sexual ornamentation, both increases and decreases, are associated with speciation.
• To test the hypothesis that divergence in ornamentation, rather than the strength of sexual selection, drives speciation.
• To explore ecological factors influencing ornamentation and speciation in estrildid finches.

Main Methods:

• Comparative analysis of color ornamentation across avian radiations, specifically estrildid finches.
• Examining the relationship between ornamentation levels, rates of ornamental evolution, and speciation rates.
• Investigating correlations between gregariousness, reproductive investment, and ornamental trait elaboration.

Main Results:

• Lineages with more elaborate ornamentation did not exhibit higher speciation rates.
• Faster rates of ornamental evolution were observed in more ornamented lineages.
• Both increases and decreases in ornamentation were significantly associated with speciation events.
• Gregariousness and reproductive investment correlated with the elaboration of certain ornamental traits.

Conclusions:

• Divergence in sexually selected ornamentation, encompassing both increases and decreases, is linked to speciation in estrildid finches.
• Ecological factors like gregariousness and reproductive investment may influence ornamentation and subsequent speciation.
• The strength of sexual selection alone may be an insufficient metric for understanding the role of ornamentation in speciation.