Gene duplication as a mechanism of adaptation

Adaptation to Environmental Toxins over Evolutionary Time

Adaptation by single nucleotide mutations and changes in their frequency is slow, and other mechanisms, such as gene duplication, have been proposed as mechanisms that would allow rapid adaptation to a changing environment (Kondrashov 2012). Environmental toxins have been present throughout evolutionary history, but have rapidly increased in variety and concentration due to human activity, providing a system in which to investigate the mutational mechanisms of rapid adaptation.

Myotis bats have structural variation in the cytochrome P450 and ABC transporter superfamilies, suggesting past selection pressure by xenobiotics. Since they are insectivores, they have the potential to be strongly impacted by anthropogenic toxins via biomagnification, and indeed have been shown to consume high concentrations of toxic microcystin from mayflies hatched in lakes with large amounts of mycrocystis cyanobacteria (Jones et al. 2022). This presents an opportunity to compare selective pressures on genes involved in xenobiotic toxin response and discover the relative contributions contributions of gene duplication vs single nucleotide mutation.

c. Chuck Graf

Lily, the big brown bat above, is an educational outreach animal who cannot be released into the wild. She is cared for by licensed wildlife rehabilitation specialists. Please do not handle wild bats without specific training and vaccines, it puts both you and them in danger.

Adaptive Duplication in Response to Variable Selection Pressures

Gene duplication is a valuable mechanism for generating genomic novelty, and for that reason may be especially beneficial in, for example, gene families involved in pathogen response or distinguishing among hundreds or thousands of volatile organic compounds.

In collaboration with Lucie Etienne's lab, we recently found that some Myotis bats have a unique duplication of protein kinase R, a protein that inhibits viral replication. The two copies have functional differences in their effectiveness against pox viruses, potentially contributing to bats' unique relationship with viruses (Jacquet et al. 2022).

In collaboration with Sharlene Santana's lab, we investigated the relationship between the behavior and specialization of three species of Carollia bats in response to volatile organic compounds produced by ripe and unripe Piper fruit. Piper plants vary in the type and concentration of volatile organic compounds they produce, and short-tailed fruit bats (Carrolia)  have within-species copy number variation of olfactory receptor genes. We found evidence of adaptive evolution of Piper in response to Carrolia dietary preferences (Leiser-Miller et al. 2020, Santana et al. 2021)