Empirical Approaches to Phylogenetic Comparative Methods in Plant Science
Pearse, William D. , Hobbie, Sarah E. , Cavender-Bares, Jeannine .
New methods to rapidly quantify (leaf) shape and model its evolution.
Plants display a wide variety of leaf structures and shapes, the function of which has been greatly debated. Botanists have developed a number of indices of leaf shape, many based around measurement of leaf perimeter, surface area, and dry mass. While these metrics have been extremely useful, they do not map directly onto leaf shape - different shapes have the same perimeter and surface area. One popular alternative (geometric morphometrics) uses manually-identified comparable points across different leaves. While these techniques are powerful, and retain a direct mapping onto leaf shape, they are time-consuming and limited to sufficiently comparable leaves. We describe a new software pipeline ('stalkless') that rapidly identifies leaves within existing images, and uses Fourier Analysis to reliably quantify leaf shape without requiring user input. We apply this method to over five thousand diversely-shaped plant leaves collected as part of the Urban Homogenization of America project. We then model the evolution of the shapes of these leaves, using a novel phylogeny built using the lead author's software pipeline ('phyloGenerator'). We comment on the mode and rate of evolution of leaf shape in these data, while cautioning that the taxonomically biased origins of our samples may have affected our results. We hope that these results and techniques will be of interest to anyone interested in quantifying, and modelling the evolution of, the shape of biological structures.
Leaf shape analysis program
Phylogeny generation program
Urban Homogenization Project
1 - University of Minnesota, Ecology, Evolution, and Behavior, USA
Leaf functional traits
Presentation Type: Symposium or Colloquium Presentation
Candidate for Awards:None