Organisms on islands look different than their mainland counterparts. The constellation of features that repeatedly evolves on islands (collectively referred to as the “island syndrome”) includes gigantism/dwarfism, higher population density, and docile behavior. Although ecological factors have been identified that associate with the island syndrome, its genetic and evolutionary causes remain mysterious. By discovering the genetic steps island organisms take to differentiate themselves from their mainland relatives, we aim to reveal mechanisms behind a repeatable evolutionary pattern.
Evolution of Big Bodies in House Mice from Gough Island
The largest wild house mice on record live on Gough Island, a remote island in the middle of the South Atlantic Ocean. It appears the mice evolved their exceptional body size in just a few hundred generations. We identified a suite of genomic regions involved in accelerating growth. The effects of these regions are consistent with natural selection driving the increase in body size. We discovered that Gough Island mice show substantial changes in gene expression in fat, liver, and brain. We are combining these insights with deep phenotyping in congenic strains and population genomics to chase down the genes responsible for this extraordinary example of the island syndrome.
Behavioral Evolution in House Mice from Gough Island
Organisms that colonize islands need to modify their behavior to match their new environments. We found that Gough Island mice show evidence of enhanced exploration and reduced anxiety in laboratory tests. We are characterizing the genetics underpinning these behavioral changes to understand how complex behaviors evolve in nature.
Population Genomics of Mice from Other Islands
Some of the strongest comparative evidence for the island syndrome comes from rodents. We are using population genomics to extend our evolutionary studies to other island populations of house mice, island populations of white-footed mice, and island populations of deer mice. In each case, island mice evolved substantial increases in body size. We aim to reconstruct the demographic histories of these intriguing populations and to determine whether the same genes were targeted by directional selection in these independent examples of the island syndrome.