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An Essay: The Stimulus of Unusual Geologies for Plant Speciation
Arthur R. Kruckeberg
Vol. 11, No. 3 (Jul. - Sep., 1986), pp. 455-463
Published by: American Society of Plant Taxonomists
Stable URL: http://www.jstor.org/stable/2419082
Page Count: 9
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Though a region's climate sets the limits for a biota, geology enriches local discontinuity and habitat diversity. When slope, exposure, and physical and chemical properties of rock and soil are arrayed discontinuously, the opportunities for events leading to speciation can occur. Several scenarios can account for evolution in geologically diverse landscapes. They range from ecotypic differentiation and disruptive selection to saltational speciation. I draw upon evidence from microevolutionary response to heavy metals and from serpentine endemism. The western North American genus Streptanthus (Cruciferae), with a number of serpentine endemics, illustrates the possible modes of evolutionary diversification on this demanding substrate.
Systematic Botany © 1986 American Society of Plant Taxonomists