Search

It has been predicted that the highly degenerate mammalian Y chromosome will be lost eventually. Indeed, Y was lost in the Ryukyu spiny rat Tokudaia osimensis , but the fate of the formerly Y-linked genes is not completely known. We looked for all 12 ancestrally Y-linked genes in a draft T. osimensis genome sequence. Zfy1, Zfy2, Kdm5d, Eif2s3y, Usp9y, Uty, and Ddx3y are putatively functional and are now located on the X chromosome, whereas Rbmy, Uba1y , Ssty1 , Ssty2 , and Sry are missing or pseudogenized. Tissue expressions of the mouse orthologs of the retained genes are significantly broader/higher than those of the lost genes, suggesting that the destinies of the formerly Y-linked genes are related to their original expressions. Interestingly, patterns of gene retention/loss are significantly more similar than by chance across four rodent lineages where Y has been independently lost, indicating a level of certainty in the fate of Y-linked genes even when the chromosome is gone. [ABSTRACT FROM AUTHOR]

Fitness landscapes map genotypes to their corresponding fitness under given environments and allow explaining and predicting evolutionary trajectories. Of particular interest is the landscape ruggedness or the unevenness of the landscape, because it impacts many aspects of evolution such as the likelihood that a population is trapped in a local fitness peak. Although the ruggedness has been inferred from a number of empirically mapped fitness landscapes, it is unclear to what extent this inference is affected by fitness estimation error, which is inevitable in the experimental determination of fitness landscapes. Here, we address this question by simulating fitness landscapes under various theoretical models, with or without fitness estimation error. We find that all eight examined measures of landscape ruggedness are overestimated due to imprecise fitness quantification, but different measures are affected to different degrees. We devise a method to use replicate fitness measures to correct this bias and show that our method performs well under realistic conditions. We conclude that previously reported fitness landscape ruggedness is likely upward biased owing to the negligence of fitness estimation error and advise that future fitness landscape mapping should include at least three biological replicates to permit an unbiased inference of the ruggedness. [ABSTRACT FROM AUTHOR]