An overarching theme of work in the lab is using function to understand broad patterns of morphological evolution. We use biomechanics, manipulative experiments, and comparative methods to explore how the performance of reproductive functions, such as spore release, pollen capture, or seed dispersal, can constrain the evolution of morphology in some cases and lead to morphological diversity in others.
One system we have focused on is a unique pollination mechanism in living conifers based on the flotation of pollen grains. Certain species of conifers produce pollen grains that are buoyant in water, and these species also produce ovules facing downwards with respect to gravity that exude an aqueous droplet called a pollination drop. This combination of features causes the buoyant pollen to float upwards and inside the ovules, which concentrates pollen grains for effective fertilization and allows the plant to “scavenge” pollen that had landed around the ovule. Previous studies in the lab have tested the efficacy of this mechanism and its evolutionary consequences through controlled pollination experiments, phylogenetic tests of the correlation among pollen morphology, ovule orientation, and drop secretion, and paleobotanical studies of the history of pollen flotation in seed plants.
We are also currently investigating spore discharge in the living lycophyte Selaginella, which has evolved several unique mechanisms to actively disperse its spores based on differences in the anatomy of the sporangium wall in conjunction with the morphology of the reproductive strobilus.
Leslie, A.B., Beaulieu, J.M., Crane, P.R., Knopf, P., and Donoghue, M.J. 2015. Trait integration and macroevolutionary patterns in the pollination biology of conifers.
Evolution 69: 1573-1583
Leslie, A.B. 2010. Flotation preferentially selects saccate pollen during conifer pollination. New Phytologist 188: 273-279.
Leslie, A.B. 2008. Interpreting the function of saccate pollen in ancient conifers and other seed plants. International Journal of Plant Sciences 169: 1038-1045.