The Botanical Review

, Volume 84, Issue 1, pp 39–78 | Cite as

Lessons on Evolution from the Study of Edaphic Specialization

  • Nishanta RajakarunaEmail author


Plants adapted to special soil types are ideal for investigating evolutionary processes, including maintenance of intraspecific variation, adaptation, reproductive isolation, ecotypic differentiation, and the tempo and mode of speciation. Common garden and reciprocal transplant approaches show that both local adaptation and phenotypic plasticity contribute to edaphic (soil-related) specialization. Edaphic specialists evolve rapidly and repeatedly in some lineages, offering opportunities to investigate parallel evolution, a process less commonly documented in plants than in animals. Adaptations to soil features are often under the control of major genes and they frequently have direct or indirect effects on genes that contribute to reproductive isolation. Both reduced competitiveness and greater susceptibility to herbivory have been documented among some edaphic specialists when grown in ‘normal’ soils, suggesting that a high physiological cost of tolerance may result in strong divergent selection across soil boundaries. Interactions with microbes, herbivores, and pollinators influence soil specialization either by directly enhancing tolerance to extremes in soil conditions or by reducing gene flow between divergent populations. Climate change may further restrict the distribution of edaphic specialists due to increased competition from other taxa or, expand their ranges, if preadaptations to drought or other abiotic stressors render them more competitive under a novel climate.


Ecological Speciation Edaphic Endemism Harsh Environments Cost of Tolerance Serpentine Metal Tolerance Parallel Speciation Geobotany Plant-Soil Relations Local Adaptation 



I would like to thank Bob Boyd, Ian Medeiros, Elizabeth Farnsworth, Susan Harrison, Tanner Harris, and Jonathan Gressel for constructive comments on earlier drafts of the manuscript. Additional comments from Mark R. Macnair and an anonymous reviewer greatly improved the manuscript. Funding from the US-Sri Lanka Fulbright Commission during the writing of this review is gratefully acknowledged.

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© The New York Botanical Garden 2017

Authors and Affiliations

  1. 1.Biological Sciences DepartmentCalifornia Polytechnic State UniversitySan Luis ObispoUSA
  2. 2.Unit for Environmental Sciences and ManagementNorth-West UniversityPotchefstroomSouth Africa

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