A long running interest in our lab group is why leaf shapes vary and how do diverse leaf shapes evolve?
We are all aware of the remarkable diversity of shapes that leaves can display. Variation ranges from developmental sequences within a shoot, to within crown response to microenvironment, from variation among species within and between communities, to variation through evolutionary lineages. Leaves, as the site of photosynthesis, are critical to plant growth and survival. As such, it is generally assumed that variation in a prominent trait like leaf shape would be functional. To this end, several theories, not mutually exclusive, have been proposed to explain leaf shape diversity. These include: thermoregulation of leaves especially in arid and hot environments, hydraulic constraints, patterns of leaf expansion in deciduous species, structural constraints, adaptations to avoid herbivory, adaptations to optimize light interception and, given that leaves are hypothesized to be developmental homologs of floral organs, selection on flower form. The relative importance of each of these factors is unclear. Research in my lab examines the functional significance of leaf shape and the evolution thereof, particularly in the genus Pelargonium.
For more on this topic see these papers from lab members:
- Leigh, A., S. Sevanto, J. D. Close and A. B. Nicotra (2017). "The influence of leaf size and shape on leaf thermal dynamics: does theory hold up under natural conditions?" Plant, Cell & Environment 40(2): 237-248.
- Leigh, A., S. Sevanto, M. C. Ball, J. D. Close, D. S. Ellsworth, C. A. Knight, A. B. Nicotra and S. Vogel (2012). "Do thick leaves avoid thermal damage in critically low wind speeds?" New Phytologist 194(2): 477-487.
- Nicotra, A., A. Leigh, C. K. Boyce, C. D. Jones, K. J. Niklas, D. L. Royer and H. Tsukaya (2011). "The evolution and functional significance of leaf shape in the angiosperms." Functional Plant Biology 38: 535-552.
- Leigh A, Zwieniecki MA, Rockwell FE, Boyce CK, Nicotra AB, Holbrook NM (2011) Structural and physiological correlates of heterophylly in Ginkgo biloba L. New Phytologist.
- Jones CS, Bakker FT, Schlichting CD, Nicotra AB (2009) Leaf Shape Evolution in the South African Genus Pelargonium L' Her. (Geraniaceae). Evolution 63(2), 479-497.
- Nicotra AB, Cosgrove MJ, Cowling A, Schlichting CD, Jones CS (2008) Leaf shape linked to photosynthetic rates and temperature optima in South African Pelargonium species. Oecologia 154(4), 625-635.