. The Canadian field-naturalist. 1984 LooMAN: Shepherd/A argentea (Pursh) Nutt, Buffaloberry 243 \.f/'^ i^. Figure 8. Rootstock oiShepherdia argentea with nodules of symbiont; the root-crown is about 10 years old. Scale about 10. Evolution and Migration No reports of studies on possible evolutionary development of 5. argentea have been seen. However, studies by Arohonka and Rousi (1980) suggest that Shepherdia is genetically closer to Hippophae than to Elaeagnus. Differences in taxonomic characters, as well as chromosome numbers and chromosome size indicate separate lines of evolution fo
. The Canadian field-naturalist. 1984 LooMAN: Shepherd/A argentea (Pursh) Nutt, Buffaloberry 243 \.f/'^ i^. Figure 8. Rootstock oiShepherdia argentea with nodules of symbiont; the root-crown is about 10 years old. Scale about 10. Evolution and Migration No reports of studies on possible evolutionary development of 5. argentea have been seen. However, studies by Arohonka and Rousi (1980) suggest that Shepherdia is genetically closer to Hippophae than to Elaeagnus. Differences in taxonomic characters, as well as chromosome numbers and chromosome size indicate separate lines of evolution for all three genera. Migration oiS. argentea in the present area of distribution is post-glacial, and may have been from the east as well as from the south. Pollen of the species have been found in late Pleistocene and Holocene deposits in the Great Lakes region (McAndrews et al. 1973). Although its occurrence in the deposits is indicated as rare, the Great Lakes region may have served as a minor emigration centre. 11. Response Behaviour (a) Fire: Although fire can cause severe damage to old stands of 5". argentea, especially when much dead wood is present, stems of 20 + years usually survive at least in part. The root systems are seldom severely damaged, and vigorous sprouting after a fire often results in increased density of the stand within a few years. (b) Grazing and harvesting: Grazing of young sprouts by rabbits, as well as browsing by deer appear to be quite common judging by the amounts of droppings observed. Only first and second year shoots appear to be eaten; older shoots usually develop sharp thorns and become less attractive. Recovery of shoots, even when grazed several years in succession, has been noted in several stands. The shrubs are of no commercial value, and are not harvested. (c) Flooding: In most of the areas where the species is common, spring flooding occurs more or less regularly. Plants do not show any adverse signs, even when surface water is s
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