Sexual Isolation Between Drosophila mojavensis and Drosophila arizonae

Abstract

Sexual, or behavioral, isolation is a form of reproductive isolation that impedes gene flow between divergent taxa. In this study, sexual isolation was measured in a sister-species pair of North American cactophilic fruitflies. The results show that interspecific behavioral isolation is dependent upon the strain of origin of D. mojavensis, but is independent of the strain of origin of D. arizonae. Interspecific sexual isolation is greatest in crosses involving D. mojavensis from sympatry, which is consistent with reinforcement, and seems to be attributable to increased reluctance by D. mojavensis females and D. arizonae males to mate with heterospecifics. Contrary to previous studies, I found strong evidence for reproductive isolation between two strains of D. arizonae. The majority of the observed behavioral isolation seems to be the result of intraspecific, interpopulation encounters between females from Southeastern Mexico and males derived from the Northern population.