Imagine combining a chimpanzee, a gorilla, and a monkey to create a tri-hybrid species; perhaps not as extreme, but that's the idea behind our laboratory research with creating a tri-hybrid fruit fly species. To our knowledge, there has not yet been any successful research conducted on the lab-generated tri-hybridization in any Drosophila species. We have created a tri-hybrid fruit fly species and are testing the resulting interactions of this hybrid crossing. Through our deliberate hybridization in a controlled laboratory environment, we have been able to hybridize these species for eight, and ongoing, non-overlapping generations. We worked with three incipient species of Drosophila athabasca species complex; Eastern-A (EA), Eastern-B (EB), and West-Northern (WN). Prior research in this lab, in combination with recent preliminary behavioral mating tests, have shown females preferentially choose to mate with males of their own species via divergence in male courtship songs. Because each species has evolved to be nearly completely sexually isolated, it was of great interest to see how sexual isolation would be broken by hybridization. This first phase of our project is to characterize the phenotypic and genotypic characteristics of our tri-hybrid species, both at the prezygotic and postzygotic levels. For prezygotic assays, we assessed male courtship song variation, copulation duration, and female mating preferences for male songs. For postzygotic assays, we observed the resulting fecundity (offspring production) of mating pairs. Our results thus far indicate a viable and proliferating tri-hybrid species as demonstrated through fecundity tracking in conjunction with courtship behavior data. We are interested in characterizing the distribution of phenotypes in the tri-hybrid species and whether our hybrids will exhibit "transgressional segregation", a phenomena where individual hybrids develop characteristics that are outside the normal phenotypic range of the original three species. Future experiments would involve creating derivative populations from the tri-hybrid species stock to track whether novel female mate preferences and their preferred male traits can coevolve anew and whether this will recreate sexual isolation over time in the laboratory.
Acknowledgements: I would like to acknowledge the mentorship provided by and partnership with Professor Roman Yukilevich through this exciting, explorative study as well as the Union College Undergraduate Research Office for providing support with funding through the Student Research Grant.