Melanism and the melanocortin-1 receptor in three species of sciuridae

Sequence variations in the melanocortin-1 receptor (MC1R) gene are associated with melanism in many different species of mammals, birds and reptiles. The grey squirrel (Sciurus carolinensis), found in the British Isles, was introduced from North America in the late nineteenth century. Melanism in the British grey squirrel is associated with a 24 base pair deletion in the MC1R. To investigate the origin of this mutation we sequenced the MC1R of melanic grey squirrels from both the British Isles and North America. Melanic grey squirrels of both populations had the same 24 base pair deletion associated with melanism. Given the significant deletion associated with melanism in the grey squirrel, we sequenced the MC1R of both wildtype and melanic fox squirrels (Sciurus niger) and red squirrels (Sciurus vulgaris). Unlike the grey squirrel, no association between sequence variation in the MC1R and melanism was found in these two species. We conclude that the melanic grey squirrel found in the British Isles originated from one or more introductions of melanic grey squirrels from North America. We also conclude that variations in the MC1R are not associated with melanism in the fox and red squirrels.