Genetics Reveal the Origin and Timing of a Cryptic Insular Introduction of Muskrats in North America

Abstract

The muskrat, Ondatra zibethicus, is a semiaquatic rodent native to North America that has become a highly successful invader across Europe, Asia, and South America. It can inflict ecological and economic damage on wetland systems outside of its native range. Anecdotal evidence suggests that, in the early 1900s, a population of muskrats was introduced to the Isles of Shoals archipelago, located within the Gulf of Maine, for the purposes of fur harvest. However, because muskrats are native to the northeastern coast of North America, their presence on the Isles of Shoals could be interpreted as part of the native range of the species, potentially obscuring management planning and biogeographic inferences. To investigate their introduced status and identify a historic source population, muskrats from Appledore Island of the Isles of Shoals, and from the adjacent mainland of Maine and New Hampshire, were compared for mitochondrial cytochrome b sequences and allele frequencies at eight microsatellite loci. Appledore Island muskrats consistently exhibited reduced genetic diversity compared with mainland populations, and displayed signatures of a historic bottleneck. The distribution of mitochondrial haplotypes is suggestive of a New Hampshire source population. The data presented here are consistent with a human-mediated introduction that took place in the early 1900s. This scenario is further supported by the zooarchaeological record and island biogeographic patterns. This is the first genetic study of an introduced muskrat population within US borders and of any island muskrat population, and provides an important contrast with other studies of introduced muskrat populations worldwide.

Zooarchaeological assemblages contextualize the historical ecology and harvest of fur-bearing mammals in Vermont

“…Zooarchaeological records can assist in the detection of non-native species, and, conversely, affirm the native status of species categorized as having been introduced (Mychajliw and Harrison, 2014;Hofman et al, 2015;West et al, 2017). Three canid species of varying "native" status currently inhabit Vermont: coyote (Canis latrans), red fox (Vulpes vulpes), and gray fox (Urocyon cineoargentatus), and the changing dynamics between them have consequences for humanwildlife conflict and zoonotic disease (e.g., Needle et al, 2020).…”

Biogeographic problem-solving reveals the Late Pleistocene translocation of a short-faced bear to the California Channel Islands

“…Islands have long been important places for evaluating fundamental ecological and evolutionary processes and are areas of significant conservation concern 1 . Yet, we are increasingly recognizing that the structures of today's island ecosystems are partly a result of human activities in the historical and more distant past, both through selective extinctions 2 and sometimes cryptic species introductions 3 . Fossil and archaeological records can play a critical role in disentangling natural versus anthropogenically-mediated dispersals with the application of emerging technical toolkits (e.g., ancient DNA, stable isotopes).…”