Scientist
Center for Conservation and Sustainable Development
Research Interests
• Species concepts and delimitations
• Spatial patterns of species diversity and distributions
• Ecological computer modeling
Is variation in leaf shape discrete? A test with Espeletia. Jiménez is an Associate Scientist in the Center for Conservation and Sustainable Development. His research program seeks to determine the factors that determine the abundance and distribution of species at various spatial scales.Many phenotypic characters used to delimit plant species are described using categories, as if phenotypic variation was largely discrete. For example, the overall shape of leaves is often described as a discrete character, using categories such as “ovate” and “obovate.” The description of phenotypic variation as if it constituted qualitative variation has a long tradition in biology, and botanists have developed standardized categories to describe variation in the shape of morphological structures (1). Yet, in principle, shape could vary continuously and the categories used by botanists may not correspond to discrete phenotypic variation. In a given group of plants, leaves could vary along a continuum between ovate and obovate. If so, treating this character as if it were discrete would impose arbitrary divisions on continuous variation, potentially leading to delimitation of taxonomic species that bear no relationship to the structure of biological diversity (2). In this project a student will test if leaf shape variation in the plant genus Espeletia is discrete, as suggested by terms used in species descriptions and identification keys (3,4). The student will use quantitative methods (5,6) to describe the overall shape of leaves, the shape of leaf apices and the extent to which leaves are “pseudopetiolate.” The frequency of these phenotypic measurements will be examined to determine if they form clusters that correspond to botanical terms describing shape (e.g., ovate, obovate, pseudopetiolate, etc.), or if these terms are arbitrary divisions of phenotypic variation. The student participating in this project will use the R environment (http://www.r-project.org/) to analyze data gathered from images of herbarium specimens. No previous experience with statistics or the R environment is needed; if the student is not familiar with the R environment or basic statistics, a strong disposition to learn a computer language and statistics is required.
References:
• Stearn, W.T., 1983. Botanical Latin, history, grammar, syntax, terminology and vocabulary, (Ed. 3). David and Charles.
• Stevens, P.F., 1991. Character states, morphological variation, and phylogenetic analysis: a review. Systematic Botany 16: 553-583.
• Cuatrecasas, J. 2013. A systematic study of the subtribe Espeletiinae (Heliantheae, Asteraceae). New York Botanical Garden Press.
• Mavárez, J., 2020. An illustrated diagnostic key to species in the Venezuelan clade of Espeletia (Asteraceae). Harvard Papers in Botany 25: 79-93.
• Balduzzi, M. et al. 2017. Reshaping plant biology: qualitative and quantitative descriptors for plant morphology. Frontiers in Plant Science 8: 117.
• Bucksch, A., et al. 2017. Morphological plant modeling: unleashing geometric and topological potential within the plant sciences. Frontiers in Plant Science 8: 900.