Dissertation Research: Adaptation and Differentiation Among Serpentine Populations of Platystemon californicus

点击翻译按钮获取中文摘要

9701323 STRATTON The chemistry of serpentine soil is such as to preclude the growth of most species of plants. This project investigates the nature of traits underlying the ability of some populations of the plant species Platystemon californicus to tolerate serpentine soil. First, the tolerance of populations growing on serpentine soil is being compared with that of populations native to other habitats. Second, the levels of nutrients and heavy metals in each of the soils are being assayed along with the physiological responses of plants from each population to variations in those same chemical factors. Third, a DNA geneaology of the populations is being produced to determine whether serpentine habitat has been colonized multiple times independently. And fourth, artificial hybridizations among serpentine populations are being performed to determine whether the genetic basis of serpentine tolerance differs among populations. Serpentine tolerance in P. Californicus appears to represent a case where natural selection is acting independently, but more or less in parallel, in geographically isolated serpentine populations. It is currently unknown whether such parallel selection pressures retard or accelerate genetic divergence among populations. That is, does parallel selection hmmogenize a species or cause it to diversify? The resolution of this issue is relevant to a number of theoretical and applied population biology problems - from the conservation of geographically fragmented species to the coordinated control of agricultural pests and human diseases.