I’ve occasionally peered at a lovely piece of species-rich grassland and wondered a) how all the different species co-exist and b) what benefit the many different leaf shapes convey. Answers on a postcard please. However, I came across some information on one tiny facet of this issue while browsing information about the methods used to infer climatic conditions in the ancient past.
Early in the 20th century two Harvard researchers – Irving W. Bailey and Edmund W. Sinnott – wanted to establish whether there were patterns in the distribution of leaf shapes across the world’s climatic zones. Through this they hoped to use fossil remains of leaves as a guide to the prevailing climate at the time of their preservation. Their work showed that there is a correlation between cooler climates and toothed leaves in woody dicots. This has now developed into a mature and well-tested method called Leaf Margin Analysis as one of many methods for determining past climatic conditions – which has immense practical relevance in the current climate crisis.
Fuller explanations can be found here and here. These two papers explore some of the reasons for this trend and consider some of the confounding factors. There appears to be a strong link between deciduous trees and toothed margins, perhaps linked to the need to establish photosynthesis in the early spring, but a weaker correlation for other types of plant.