Surprisingly weak coordination between leaf structure and function among closely-related tomato species

Natural selection may often favor coordination between different traits, or phenotypic integration, in order to most efficiently acquire and deploy scarce resources. As leaves are the primary photosynthetic organ in plants, many have proposed that leaf physiology, biochemistry, and anatomical structure are coordinated along a functional trait spectrum from fast, resource-acquisitive syndromes to slow, resource-conservative syndromes. However, the coordination hypothesis has rarely been tested at a phylogenetic scale most relevant for understanding rapid adaptation in the recent past or predicting evolutionary trajectories in response to climate change. To that end, we used a common garden to examine genetically-based coordination between leaf traits across 19 wild and cultivated tomato taxa. We found surprisingly weak integration between photosynthetic rate, leaf structure, biochemical capacity, and CO2 diffusion, even though all were arrayed in the predicted direction along a 'fast-slow' spectrum. This suggests considerable scope for unique trait combinations to evolve in response to new environments or in crop breeding. In particular, we find that partially independent variation in stomatal and mesophyll conductance may allow...Continue Reading