Factors Determining Heterospecific Mating Success in the Sibling Fruit Fly Species Drosophila Pseudoobscura and D. Persimilis

Abstract

Patterns of heterospecific matings are important to understand in order to learn about speciation. I proposed a classical signal detection model as a representation of heterospecific mating patterns in both sexes. From the model I proposed that males would be able to achieve successive heterospecific mating success, as those males were more similar to conspecifics. I also proposed that restrictive females that rejected heterospecific matings would also be more likely to reject conspecific matings. I used the sibling species Drosophila pseudoobscura and D. persimilis to examine heterospecific mating patterns in males and females. I found that males previously accepted as heterospecific mates were more likely to achieve heterospecific matings than males that had previously been rejected as heterospecific mates. This was most likely due to decreased courtship by rejected males. Males rejected heterospecifically but mated conspecifically also were less likely to achieve heterospecific matings than males that had initially been accepted as heterospecific mates. This indicated that the same males were able to achieve successive heterospecific matings, despite rejected males also having had initial mating success. This was again likely influenced by decreased courtship in rejected males. Furthermore, I found that females that rejected heterospecific males were also more likely to reject conspecific males than naive females. There was also a non-significant trend of females that previously accepted heterospecific males were more likely to again accept heterospecific males than females that had previously rejected heterospecific males.