View Program - 2022 Population, Evolutionary, and Quantitative Genetics Conference

Organisms on islands often evolve extreme phenotypes. Novel environmental conditions such as a lack of predators can shift long-standing adaptive peaks to new optima. House mice from Gough Island are a prime example of rapid and extreme phenotypic evolution following island colonization. These mice have nearly doubled in body size and frequently predate on nesting seabirds. We hypothesized that an absence of both natural predators and man-made shelters stimulated the evolution of increased boldness and exploration in mice from Gough Island. To test this hypothesis, we conducted a series of behavioral tests in a controlled laboratory setting using wild-derived inbred strains of mice from Gough Island and the Eastern United States. Open field and light/dark box tests show Gough Island mice are more active and spend more time in open, brightly lit areas than mainland mice. Exploration-related behaviors are influenced by age, sex, and parental identity whereas boldness-related phenotypes are not, suggesting that these two behavioral classes are genetically separable. To identify loci associated with the evolution of exploration and boldness, we used open field and light/dark box tests to quantify the behavior of 638 F2 mice generated by intercrossing Gough Island mice with mice from the mainland strain. Measures of exploration and boldness are uncorrelated in F2s further suggesting they are genetically separable while body size is slightly negatively correlated with exploration. F2 mice were genotyped at 31,683 single-nucleotide polymorphisms informative in the cross. We report quantitative trait loci (QTL) for exploration-related and boldness-related behaviors, providing one of the first portraits of the genetic architecture of the island syndrome. We also describe genetic effects of mice on the behaviors of their cage-mates (indirect genetic effects).

Genetics of behavioral evolution in giant mice from a predator-free island.