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Conservation biologists are generally united in efforts to curtail the spread of non-native species globally. However, the colonization history of a species is not always certain, and whether a species is considered non-native or native depends on the conservation benchmark. Such ambiguities have led to inconsistent management. Within the Tongass National Forest of Alaska, the status of American marten (Martes americana) on the largest, most biologically diverse and deforested island, Prince of Wales (POW), is unclear. Ten martens were released to POW in the early 1930s, and it was generally believed to be the founding event, although this has been questioned. The uncertainty surrounding when and how martens colonized POW complicates management, especially because martens were selected as a design species for the Tongass. To explore the history of martens of POW we reviewed other plausible routes of colonization; genetically and isotopically analyzed putative marten fossils deposited in the late Pleistocene and early Holocene to verify marten occupancy of POW; and used contemporary genetic data from martens on POW and the mainland in coalescent simulations to identify the probable source of the present-day marten population on POW. We found evidence for multiple routes of colonization by forest-associated mammals beginning in the Holocene, which were likely used by American martens to naturally colonize POW. Although we cannot rule out human-assisted movement of martens by Alaskan Natives or fur trappers, we suggest that martens be managed for persistence on POW. More generally, our findings illustrate the difficulty of labeling species as non-native or native, even when genetic and paleo-ecological data are available, and support the notion that community resilience or species invasiveness should be prioritized when making management decisions rather than more subjective and less certain conservation benchmarks., (© 2015 Society for Conservation Biology.)