Latest Pleistocene (17,500–13,500 cal yr BP) Arctic ground squirrel (Sciuridae: Urocitellus parryii) middens record late persistence of steppe-tundra in central Yukon Territory

Abstract

This paper presents the palaeoecological analysis of five latest Pleistocene (17,500–13,500 cal yr BP) Arctic ground squirrel (Urocitellus parryii) middens from three sites in the Klondike goldfields of central Yukon Territory. Plant and invertebrate macrofossil records were represented by 24 and 20 taxa, respectively, providing a record of the local environment and the earliest known occurrences in Yukon Territory for several taxa (e.g., the robber fly [Lasiopogon sp.] and marsh yellowcress [Rorippa cf. palustris]). The plant and invertebrate assemblages indicate the persistence of steppe-tundra to at least 13,680 cal yr BP by the preservation of taxa typically occupying dry sites, many of which remain components of grasslands and south-facing azonal steppe communities in present-day Yukon Territory. In the context of shrub expansion that is documented to have occurred by 14,000 cal yr BP in interior Alaska, we consider the taphonomic biases associated with Arctic ground squirrel middens that may lead to the lack of shrub macrofossils preserved at the sites. Our study provides an ecologically unique and chronologically constrained perspective on the local persistence of steppe-tundra in easternmost Beringia despite the regional expansion of shrubs.