Investigating sperm competition in two geographically isolated populations of Drosophila mojavensis

Sexual conflict, female choice and male-male competition are frequently exemplified in polygamous mating systems. In such systems, fertilization success may be determined by both female selection and male competition in the female reproductive tract. Sperm competition is evident when there is unequal fertilization success of sperm from different male competitors. However, the factors that determine the winners in sperm competitions are often multifaceted. Observation of paired, coevolved female and male reproductive traits in many taxa leads people to predict coevolved male precedence in sperm competition assays. On the other hand, 2nd male precedence or last male precedence is often evident in polygamous species, showing strong ability of the last male who involves in consecutive matings to manipulate in favor of his reproductive interest. In my study, I show that in two recently diverged, yet geographically isolated Drosophila mojavensis populations, sperm competition scenarios are different, with one population exhibiting stronger ability to manipulate when play as 2nd male, potentially owing to differentiated habitat ecology that shaped encounter rate and resource availability distinctly in different fly populations.