The Project
The Project
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Introduction
Introduction
Sex chromosomes are key players in reproduction and genome evolution, but the Y chromosome’s role is often overlooked due to its degeneracy and low gene content. In Drosophila pseudoobscura, where the Y chromosome remains polymorphic, we investigate whether variation in Y chromosome size and structure influences male fertility and reproductive success.
Figure 1. Y chromosomes show geographic structure with different chromosomes being more frequent across the species range. This figure shows three common Y types in CA. Modified from Dobzhansky 1935.
Figure 2. D. Pseudoobscura Y chromosomes differ in absolute size and the location of the centromere. Example Y chromosomes from Dobzhansky 1935.
Methodology
Methodology
We selected five strains differing in Y chromosome size and structure Males and females were collected as virgins and aged for 7–10 days to ensure reproductive maturity. Virginity was confirmed by inspecting vials for absence of larvae. To assess fertility, we set up single-pair crosses (one male and one female per vial), evenly distributing females across male genotypes to minimize block effects.
Table 1. Y chromosome Characteristics and Origin of Selected Drosophila pseudoobscura Strains.
Figure 3. Timeline of Experimental Protocol for Fertility Assessment.
Results
Results
Males with different Y chromosomes showed variation in fertility, as measured by progeny count. The KB10 strain had the highest average progeny production, while Ref had the lowest. 105 and KB4 showed intermediate fertility, and 124 was similar to Ref. These patterns suggest that Y chromosome differences may contribute to male reproductive success.
Figure 4. Variation in Male Fertility Measured by Progeny Counts Based on Y Chromosome Genotype.
Conclusion
Conclusion
These findings suggest that Y chromosome polymorphism influences male fertility in Drosophila pseudoobscura. The variation in progeny counts across genotypes may reflect differences in fertility gene expression, likely tied to Y chromosome transposable element content. Comparing these results to findings in D. melanogaster highlights the evolutionary divergence between species and shows the potential plasticity of sex chromosome function in shaping reproductive traits.
These results may also offer parallels in human health. In humans, Y chromosome variation has been associated with infertility and altered gene expression, making Dpse a useful model for investigating how subtle differences in Y structure can influence male fertility across taxa.
Ongoing Work
Ongoing Work
Building on this initial fertility screening, we are in the process of generating Y chromosome substitution lines to isolate the effects of Y-linked variation from autosomal and X-linked background.
Figure 5. Diagram depicting Y chromosome substitution.
We expect that if fertility differences persist after Y substitution, it will support the hypothesis that Y-linked structural variation directly affects male fertility.
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