History of habitat and the decline of the Vancouver Island Marmot (Marmota vancouverensis) [Histoire de l'habitat et du déclin de la marmotte de l'île de Vancouver (Marmota vancouverensis)].

Résumé

Vegetation changes in subalpine and alpine habitats on Vancouver Island may have had a role in today’s low numbers of Vancouver Island marmots (Marmota vancouverensis). We describe a fecal dietary analysis and approximately 2000 years of dynamic vegetation history of marmot habitat. Twelve fecal samples collected between May and August 2003 in the Mount Washington area were analyzed for pollen and spores to determine marmot diet. The main pollen types in the feces were derived from non-arboreal plants associated with open environments, including Ericaceae, Liliaceae, Rosaceae, and Cyperaceae family members. High-resolution pollen and spore analysis of wetland sediments collected at Heather Mountain, a locality presently inhabited by marmots, strongly suggest that subalpine forest vegetation is negatively correlated with early seral and meadow indicators, and early seral stages are positively correlated with meadow taxa. Eight times in the last 2000 years, open plant communities dominated the landscape. We infer that meadow/open parkland or transitional environments prevailed throughout approximately 78% of the sampling interval, with high percentages of alder, suggesting that this ecosystem was maintained by disturbances, likely fire. Our results demonstrate the importance of open heath and meadow habitats to marmot diet. We infer that subalpine landscapes on Heather Mountain were frequently much more open during the last two millennia than today, and were likely a complex mosaic of forested, transitional, and meadow plant communities.