BATS AND THE CONVERGENT EVOLUTION OF COMPLEX TRAITS
Lambert, Matthew James
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Convergent phenotypic evolution, the independent acquisition of similar traits in distinct species, is widespread in nature. Phenotypic convergence is a useful model for studying adaptive evolution because these instances provides researchers with naturally replicated events and provide insights into the constraints on evolution in the face of similar selective pressures. Convergence can also occur at the genetic level, when protein coding sequences in distinct species evolve to appear more closely related than the true phylogeny would indicate. Much like phenotypic convergence, molecular convergence is often interpreted as adaption to common selective pressures faced by distinct species. The study of molecular convergence offers the opportunity to understand the constraints on evolution, as well as the potential to identify the genetic bases for convergent traits. Bats are a powerful model to study molecular convergence, as this order possesses several relevant, novel traits that are rarely found in other mammals, such as extreme longevity, vocal learning and echolocation. Understanding how such complex phenotypes arise remains a fundamental goal of evolutionary biology, with ramifications that may have potential impacts on human health and wellness. Here, I study the molecular convergence of several long-lived species of bats with the longest living rodent, the naked-mole rat. I find that these long-lived, yet small-bodied mammals share a large excess of convergent substitutions in the gene ADAMTS9, which inhibits tumor formation by blocking the activity of the senescence drivng mTOR. Although mTOR is a known aging gene, ADAMTS9 has not previously been described as a longevity promoting gene. Also, to better understand the genetics of vocal learning, a rare trait that represents a crucial component of human language abilities, I study bats converging with human. I found that Rousettus aegyptiacus and human, share an excess of convergent substitutions in two genes RCOR1 and ACTN2. Lastly, I have tested for sequence convergence between bats and echolocating whales. I have found that molecular convergence in auditory genes between bats and dolphins is not nearly as common as previously reported and provide evidence suggesting multiple origins of echolocation within bats.