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

[701323]斯特拉顿蛇纹石土壤的化学性质使大多数植物无法生长。该项目调查了一些植物物种加利福尼亚盘系植物耐受蛇形土壤的能力的性状的性质。首先，将生长在蛇形土壤上的种群的耐受性与生长在其他生境的种群的耐受性进行比较。其次，正在分析每种土壤中的营养物质和重金属水平，以及每个种群的植物对这些相同化学因素变化的生理反应。第三，正在制作蛇形动物种群的DNA家谱，以确定蛇形动物的栖息地是否曾被独立地殖民过多次。第四，在蛇形虫种群间进行人工杂交，以确定不同种群间蛇形虫耐受性的遗传基础是否存在差异。蜿蜒的公差在p Californicus似乎代表了一个独立情况下自然选择作用,但并行或多或少,在地理上孤立的蜿蜒的人群。目前尚不清楚这种平行的选择压力是否会延缓或加速种群间的遗传分化。也就是说，平行选择是使一个物种趋同还是使其多样化？这一问题的解决关系到许多理论和应用的种群生物学问题——从保护地理上分散的物种到协调控制农业害虫和人类疾病。

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.