Biogeographic evidence for the evolution of chemical defense by boreal birch and willow against mammalian browsing
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Authors: J. P. Bryant, J. Tahvanainen, M. Sulkinoja, R. Julkunen-Tiitto, P. Reichardt, and T. Green
Date: 1989
Journal: The American Naturalist
Volume: 134
Number: 1
Pages: 20-34
Summary of Methods: The level of secondary chemical compounds and palatability of birch (Betula) and willow (Salix) with varied historic levels of browsing pressure were examined in a series of experiments using free-ranging and captive Alaskan snowshoe (Lepus americanus) and Finnish mountain hares (L. timidus). Concentrations of secondary defensive compounds of birch and willow from four geographic regions (Alaska, Iceland, Siberia and Finland) were determined though chemical analysis. Preference for each species was determined through a series of feeding and garden trials with free ranging and captive hares in both Alaska and Finland.
Article Summary / Main Points: Palatability increased as the level of secondary defensive compounds and the level of historic browsing pressure decrease. Winter browsing by mammals and the 10 year Alaskan hare population cycle has selected for boreal woody plants that possessed or developed chemical defenses in winter. Alaskan birch and willow were the least palatable shrubs in all of the experiments, compared to Finnish shrubs and Siberian shrubs. The most palatable is the Icelandic shrub that didn't evolve with hare browsing.
Vegetation Types: All Forest and Woodlands Riparian and Wetlands
MLRA Ecoregions: Not Applicable
Agrovoc Control Words: Riparian zones Browse Wildlife
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: birch, betula, willow, salix, alaskan snowshoe hares, lepus americanus, boreal forest, winter, chemical defense
Annotation: This paper included comparative studies in Finland and North America (Alaska). The results of this study illustrate how pressure from a consumer and population cycles (if present) can influence the evolution and shifts within a plant community.
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