Format: ORAL

Miles Berkey

Department of Biology, Western Washington University, Bellingham, USA

Ice age refugia were ecologically stable areas that remained ice-free during the Pleistocene glaciations. As a result, they offered a level of suitable conditions to host arctic species associated with theclimate of that time. About 16,400 years ago, the climate began to warm, the ice sheets in western North America began to recede, and these vestiges of the late Pleistocene became surrounded by the temperate ecosystems of today leaving disjunct and isolated species of a previous climate. A unique balance of microclimatic and topographical factors has allowed for these remnant species to exist today. Throughout the Pleistocene, ice age refugia were drivers of speciation, and currently are retainers of relictual species. Therefore, these places are biodiversity hotspots providing key insights into evolutionary histories of northern taxa. However, complete biological inventories of these places are lacking and many ice age refugia remain undetected. Tragically, due to climate change, these ecologically novel places are at risk due to the projected changes in moisture and temperature regimes for western North America. This study takes a comparative bryophyte floristics approach to detect an ice age refugium in an area of the northern Cascade Mountains of Washington state Barlow pass. The results of two years of field work yields numerous disjunct northern taxa such as Cyrtomnium hymenophylloides, Psilopilum laevigatum and Macrodiplophyllum imbricatum found within a microclimatically significant area of Barlow Pass while absent from similar areas in the glaciated North Cascades. The maximum extent of the Cordilleran ice sheet is paired with reconstructions of the local paleo-alpine glaciers, suggesting that these species are relicts of an ice-free corridor during the last glacial maximum. Finally, the bryoflora of Barlow Pass is compared with floras of putative ice age refugia and is placed in the context of North American ice age refugia.