Distribution and biogeography of the Alaskan hare (Lepus othus)

Abstract

The Alaskan Hare (Lepus othus Merriam 1900) is the largest lagomorph in North America but remains one of the most poorly studied terrestrial mammals on the continent. Its current distribution is restricted to western Alaska south of the Brooks Range, but historical anecdotal accounts of occurrences north of the Brooks Range (the North Slope) have led to confusion over its past, present, and predicted distribution. To clarify the historical range of L. othus, we surveyed North American museum collections and georeferenced voucher specimens (Supplemental File Appendix 1.1). We also located a specimen from the North Slope of Alaska long presumed lost and whose identity had come to be questioned. The rediscovery of this missing specimen suggests the occurrence of at least one Alaskan Hare on the North Slope as recently as the late 1800s. Because unforested ecosystems such as tundra and Arctic grasslands have decreased in Alaska since the last glacial maximum, and L. othus occurs in unforested habitat, we expected to observe low genetic diversity in the mitochondrial control region of L. othus. However, with recently collected specimens from regions in Alaska that were poorly represented in the past (i.e. Alaska Peninsula, Little Diomede, and Kotzebue Sound), we discovered more genetic diversity and population structure than was found in previous studies, including similar haplotypes from the Alaska Peninsula and from eastern Russia. This suggests there may have been 2 distinct colonization events of northern hares in Alaska, or introgression from L. timidus and a mitochondrial sweep that has been restricted to the Alaska Peninsula and Bristol Bay area. Our morphological analyses of the difference between the two subspecies, L. o. othus and L. o. poadromus, were ambiguous, with principal components analysis and simple linear regression indicating the presence of a latitudinal size cline and discriminant function analysis revealing successful group assignment that is not solely based on latitude. Our research clarifies the current and recent distribution of the Alaskan Hare and reveals more genetic diversity than previously suspected in the mitochondrial control region. We also observed a new biogeographic pattern and closer mtDNA association with L. timidus, which, combined with new island specimens and observations, suggests gene flow across the Bering Strait. It also highlights the importance of maximizing sample sizes and sampling widely across a taxon’s geographic distribution.