LAUSR

Isle Royale (western Lake Superior, USA) is a geographically isolated archipelago with the potential to sustain endemic populations. The island has served as an ecological model for predator–prey interactions between wolves and moose, but little is known about the 17 other mammalian inhabitants. Previous studies of locally abundant red squirrels (Tamiasciurus hudsonicus) described phenotypic differences in pelage colour and skull size, resulting in the classification of an endemic Isle Royale subspecies (T. h. regalis). However, the phylogenetics of this putative subspecies have not been explored. We sequenced mitochondrial DNA to compare haplotypes and genetic variation of seven red squirrels from Isle Royale to 42 other individuals sampled across North America. We detected 25 haplotypes in total, and four haplotypes within Isle Royale. Sequences obtained from red squirrels inhabiting Isle Royale were not unique and were shared with individuals from across the Great Lakes Region and north-eastern North America. Our results indicate that extant T. hudsonicus on Isle Royale are polyphyletic and should not be considered a unique subspecies. These findings suggest that Isle Royale is less insular and more connected than previously assumed and highlights the need to investigate the origins of other taxa in putatively isolated systems, including Isle Royale.