This project uses a stalk-eyed fly species in which females show strong mating preference for males with very exaggerated eyespan. Some males carry meiotic drive genes that cause Y-bearing sperm to malfunction – so only X-bearing sperm survive and broods are strongly female biased. While drive spreads by selfishly exploiting meiotic segregation, it disrupts individual fitness by corrupting gametogenesis and maintaining a deleterious chromosomal inversion.
We will test the intriguing hypothesis that there are counter-adaptations to the destruction of sperm in drive males. We know already that drive males have larger testes to cope with the loss of sperm. How does this influence drive male performance in competition with ejaculate from other males? We will also study how male fertility suffers due to condition-dependent effects of deleterious alleles on drive chromosomes, amplified under environmental stress.
The experiments will use genetic, behavioural and genomic assays. We will compare sperm allocation strategies of drive-bearing and standard males across a range of adult stresses. This will reveal whether sperm delivery of drive males is compromised with increasing environmental stress. Also, we will measure the success of drive males under sperm competition in challenging circumstances that allow multiple mating, reflecting the polyandrous mating system that is typical of stalk-eyed flies. Overall our project will provide better understanding of counter-adaptations to selfish genetic elements.