Although speciation has been a central focus in evolutionary biology for more than a century, there are very few case studies where we have a good understanding of the exact forces that may have acted in the diversification of a group of organisms. In order to examine such forces, botanists have often focused on closely related plants that are found under contrasting soil conditions. The study of such edaphically differentiated plants has provided valuable insight to the role of natural selection in evolution. This paper discusses several key studies that have appeared in the literature in the last half century emphasizing the role unusual soil conditions—such as those found on serpentinite outcrops, mine tailings, guano deposits, and salt flats—can play in the diversification of plant species. Many of these studies have not only shown adaptive differentiation in response to various edaphic features, but have also attempted to examine the link between adaptive traits and traits that are directly responsible for reproductive isolation between the divergent taxa. With the advent of novel genetic techniques and an increased understanding of the genetic architecture of various adaptive traits dealing with substrate tolerance, it will soon be possible to demonstrate the central role of the edaphic factor in plant evolution.



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NOTE: At the time of publication, the author Nishanta Rajakaruna was not yet affiliated with Cal Poly. This is an electronic version of an article published in International Geology Review.

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