Natural selection and the reinforcement of mate recognition.

Natural selection on mate recognition may often contribute to speciation, resulting in reproductive character displacement. Field populations of Drosophila serrata display reproductive character displacement in cuticular hydrocarbons when sympatric with Drosophila birchii. We exposed field sympatric and allopatric populations of D. serrata to experimental sympatry with D. birchii for nine generations. Cuticular hydrocarbons of field allopatric D. serrata populations evolved to resemble the field sympatric populations, whereas field sympatric D. serrata populations remained unchanged. Our experiment indicates that natural selection on mate recognition resulted in the field pattern of reproductive character displacement.