The genetic basis of body size traits in island mice. (a) Body weight, (b) sacrum length, (c) lean mass and (d) size-corrected lean mass in male wild- and captive-born island and mainland mice. Box plots indicate median, interquartile range (IQR) and at most ± 1.5 IQR from hinges. See Methods for statistical details. n.s., not significant; *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001. (Online version in colour.)