Investigation of convergent evolution with the southern marsupial mole and other subterranean mammals
Authors: Sarah Lucas 1; Stephen Frankenberg 2; Charles Feigin 3; Andrew Pask 2; Nathan Clark 1
Affiliations: 1) University of Utah, Salt Lake City, UT, USA; 2) University of Melbourne, Parkville, Victoria, Australia; 3) Princeton University, Princeton, NJ, USA
Keywords: Comparative genomics & genome evolution
Despite it being millions of years since the rare southern marsupial mole (Notoryctes typhlops) shared a common ancestor with any of the fossorial placental mammals, these species share several physiological adaptions for tunneling: tubular bodies, enlarged forepaws, reduced vision, and likely a tolerance for hypoxic conditions. When species exhibit similar phenotypes, these are often accompanied with similar genomic changes. Our group is specifically interested in what changes resulted in the species’ severely degraded eye phenotype. For unlike the other subterranean placental mammals, this species lacks both a pupil and an optic nerve. Eye development is a highly conserved and regulated developmental process. To determine what genes are undergoing convergent relaxed evolution within the marsupial mole and other subterranean species, we used RERconverge, an R statistical package. By adding two additional subterranean species to our analysis (marsupial mole and Damaraland mole-rat), this will increase the power for detecting genes associated with degraded eyesight while burrowing. We will also be able to characterize novel changes found only within the marsupial mole. As one of the oldest fossorial mammals, this will allow for more inactivating mutations to fixate within this lineage generating a stronger relative evolutionary rate (RER) signal within the species. With the increased statistical power, some genes associated with vision which were nearly significant in the previous analysis will likely become significant. Knowledge of potentially inactivating substitutions will be useful in trying to diagnose individuals with rare congenital eye malformations.