Meeting Abstract
Organismal biology often advances through two iterative stages: 1) analyzing models that integrate fundamental physical and chemical laws with biology to predict which phenotypes natural selection favors under what ecological conditions; and 2) testing model predictions by comparing observed patterns of trait evolution with that predicted by competing models. I use stomata, the microscopic valves on the leaf surface that regulate carbon uptake and water loss, as a model system for addressing basic questions about organismal physiology and evolution. In most plants, stomata are located only on the lower leaf surface, but many plants have stomata on both surfaces. The distribution of these phenotypes is highly nonrandom across flowering plants, indicating evolutionary constraint, but not necessarily adaptation. To predict the distribution of phenotypes under an adaptive hypothesis, I analyze an evolutionary physiological model based on leaf biophysics to ask how stomatal traits should evolve along light gradients. Compared to an alternative model of developmental constraint, the evolutionary physiological model explains several independent patterns of stomatal evolution in flowering plants. The combination of integrative models and comparative biology indicate that stomatal evolution is an important part of adaptation to different light environments. More broadly, investigating stomatal evolution provides new insight into major questions about the evolution of organismal form that are especially to challenging to study.
