Are traits that experience reinforcement also under sexual selection?

Area of Science:

• Evolutionary Biology
• Speciation
• Behavioral Ecology

Background:

• Closely related species in sympatry can experience reinforcement, leading to the evolution of reproductive isolation.
• Drosophila serrata coexists with Drosophila birchii in northern Australia, presenting a natural system to study reinforcement.
• Reproductive character displacement occurs when traits involved in species recognition also influence within-species mate choice.

Purpose of the Study:

• To investigate reproductive character displacement in Drosophila serrata populations along a contact zone with Drosophila birchii.
• To determine if cuticular hydrocarbons (CHCs) show genetically based differences between sympatric and allopatric populations of D. serrata.
• To assess female mate preference for male CHCs in sympatric versus allopatric populations.

Main Methods:

• Studied a 36-km transect across sympatric and allopatric populations of D. serrata.
• Analyzed male and female cuticular hydrocarbons (CHCs) using genetic and latitudinal analyses.
• Conducted experimental sympatry in the laboratory to observe CHC changes.
• Assessed female mate preference for male CHCs from different populations.

Main Results:

• Significant, genetically based differences in male CHCs were found between sympatric and allopatric D. serrata populations.
• Female CHCs varied latitudinally across the contact zone.
• Experimental sympatry induced the same directional changes in male CHCs observed in natural populations.
• Females from allopatric populations preferred allopatric-like male CHCs over sympatric-like CHCs.

Conclusions:

• Reinforcing selection from D. birchii is sufficient to cause reproductive character displacement in D. serrata.
• Male CHC evolution in response to sympatry may compromise male attractiveness in allopatric regions.
• This may prevent the spread of sympatric-like CHC blends into allopatric areas, maintaining reproductive isolation.