SELECTION FOR SEXUAL ISOLATION BETWEEN GEOGRAPHIC FORMS OF DROSOPHILA MOJAVENSIS. I. INTERACTIONS BETWEEN THE SELECTED FORMS.

Drosophila mojavensis comprises three geographic forms occurring in the United States, the Baja California peninsula, and mainland Mexico. Peninsular and mainland forms were selected for increased sexual isolation from each other, while controls were maintained with maximum outbreeding. Response to selection was highly asymmetrical in that isolation was very high between selected peninsular males and mainland females, but nonexistent between selected mainland males and peninsular females. The heightened isolation is primarily due to some change in the peninsular males.