Center for Conservation and Sustainable Development
• Species concepts and delimitations
• Spatial patterns of species diversity and distributions
• Ecological computer modeling
Did botanists poison Darwin’s mind about the nature of species? Dr. Jiménez is an ecologist at the Missouri Botanical Garden, his research focuses on understanding the determinants of the abundance and distribution of species. Species are basic units in ecology, biogeography and conservation biology. In these disciplines species are generally assumed to be phenotypically cohesive (discrete) entities that may often be reproductively isolated. In other words, these disciplines typically assume that species are real biological entities (sensu Coyne & Orr 2004, pages 9-25; Barraclough & Humphreys 2015). However, several botanists have been notorious for expressing doubts about the existence of plant species. They see species as arbitrary divisions of biological diversity that do not necessarily correspond to discrete phenotypic or reproductively isolated groups of organisms (Levin 1979, Raven 1986, Bachmann 1998). Darwin seemed to have developed a similar view (see Mayr 1982, Mallet 2013): ‘‘…we shall have to treat species in the same manner as those naturalists treat genera, who admit that genera are merely artificial combinations made for convenience. This may not be a cheering prospect, but we shall at least be freed from the vain search for the undiscovered and undiscoverable essence of the term species’’ (Darwin 1859, page 485). Moreover, it has been suggested that botanists influenced Darwin’s view about the nature of species (Mayr 1982). Perhaps more precisely, botanists have been accused of poisoning Darwin’s mind about the nature of species (Riesberg et al. 2006). Botanists could be guilty as charged if they were overly impressed by a few examples of fuzzy species limits (e.g., blackberries , dandelions and oaks) and wrongly assumed these “botanical horror stories” to be representative of plant species overall (Diamond 1992). A review of the phenotypic cohesiveness (discreteness) of plant species and its relationship to reproductive isolation suggests this was indeed the case (Riesberg et al., 2006). This review found phenotypically cohesive units that correspond to reproductively isolated groups in the majority of sexual plant taxa examined. However, the studies of phenotypic cohesion reviewed by Riesberg et al. (2006) were based on highly subjective, graphical methods that may convey little information about phenotypic groups (Cadena et al. 2017). In this REU project, students will i) compile as much data as possible from the original studies of phenotypic cohesion and reproductive isolation reviewed by Riesberg et al. (2006), ii) re-analyze the compiled data to test for phenotypic cohesion using more objective statistical methods (based on normal mixture models, Cadena et al. 2017), and iii) use the results of the re-analysis to re-evaluate the relationship between phenotypic cohesiveness and reproductive isolation. This project may be run as a collaboration between two REU students, but it may also be carried out by a single REU student. The student(s) participating in this project will use the R environment (http://www.r-project.org/) to manipulate data and perform all statistical analyses. No previous experience with statistics or the R environment is needed; but if the student is not familiar with the R language or basic statistics, strong disposition to learn a computer language and statistics is required.
• Bachmann, K., 1998. Species as units of diversity: an outdated concept. Theory in Biosciences 117: 213-230.
• Barraclough, T.G. & Humphreys, A.M., 2015. The evolutionary reality of species and higher taxa in plants: a survey of post‐modern opinion and evidence. New Phytologist, 207: 291-296.
• Cadena, C.D., Zapata, F. & Jiménez, I. 2017. Issues and Perspectives in Species Delimitation using Phenotypic Data—Atlantean Evolution in Darwin’s Finches. Systematic Biology p.syx071.
• Coyne, J. A. & Orr, H. A. 2004. Speciation. Sunderland, MA: Sinauer Associates.
• Darwin, C. 1859. On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life, 1st edn. London: John Murray.
• Diamond, J.M. 1992. Horrible plant species. Nature 360: 627-628.
• Levin, D.A., 1979. The nature of plant species. Science, 204: 381-384.
• Mallet J. 2013. Species, concepts of. In: Levin SA editor. Encyclopedia of Biodiversity. Vol. 6.
• Mayr, E. 1982. The growth of biological thought: Diversity, evolution, and inheritance. Harvard University Press.
• Raven, P. H. 1986. Modern aspects of the biological species in plants. In: Modern aspects of species (eds Kunio Iwatsuki, Peter H. Raven, and Walter J. Bock). University of Tokyo Press.
• Rieseberg, L.H., Wood, T.E. & Baack, E.J. 2006. The nature of plant species. Nature 440: 524 526.