How genetics, history and geography limit potential explanations of invasions by house mice Mus musculus in New Zealand

The distribution of distinct genetic lineages of mice in New Zealand, combined with historical records of shipping routes, political decisions, market prices, trading patterns and immigration policy, suggest that two distinct lineages of Mus musculus travelled separate routes to reach opposite ends of New Zealand in early pre-colonial times (1792–1830). (1) Mus musculus castaneus could have colonised the southern South Island between 1792 and 1810, with sealers returning from the Canton fur market, but these voyages were illegal (=undocumented) because direct trading with China was prohibited until after 1813. Signs that the potential links between the South Island and Canton were seldom used after 1810 include: (a) the Canton sealskin market was already rapidly declining in profitability by the time sealers switched to New Zealand from Bass Strait in 1804; (b) the Otago colonies of fur seals (Arctocephalus forsteri) were exhausted after 1810; (c) M. m. castaneus is absent from the southern offshore islands repeatedly visited by Sydney-based sealers after 1810. (2) M. m. domesticus had multiple well-documented opportunities to colonise the Bay of Islands with traders from Australia after 1821, and both the Cook Strait area and the southern South Island with whalers after 1829. After 1840, multiple haplotypes of M. m. domesticus from different European sources accompanied the organised settlement of New Zealand by European colonists.