Data from: Phenotypic and developmental dissection of an instance of the island rule

Organismal body weight correlates with morphology, life history,
physiology, and behavior, making it perhaps the most telling single
indicator of an organism’s evolutionary and ecological profile. Island
populations provide an exceptional opportunity to study body weight
evolution. In accord with the “island rule,” insular small-bodied
vertebrates often evolve larger sizes, whereas insular large-bodied
vertebrates evolve smaller sizes. To understand how island populations
evolve extreme sizes, we adopted a developmental perspective and compared
a suite of traits with established connections to body size in the world’s
largest wild house mice from Gough Island and mice from a smaller-bodied
mainland strain. We pinpoint 24-hour periods during the third and fifth
week of age in which Gough mice gain exceptionally more weight than
mainland mice. We show that Gough mice accumulate more visceral fat
beginning early in postnatal development. During a burst of weight gain,
Gough mice shift toward carbohydrates and away from fat as fuel, despite
being more active than and consuming equivalent amounts of food as
mainland mice. Our findings showcase the value of developmental phenotypic
characterization for discovering how body weight evolves in the context of
broader patterns of trait evolution.