Variable leaf shape on short and long shoots: an elliptic Fourier analysis of Prunus microcarpa C.A.Mey

This study uses elliptic Fourier analysis to explore the differences in shape between two subspecies of Prunus microcarpa from southeastern Turkey, as well as the differences between their short- and long-shoot leaves. Prunus microcarpa is a deciduous shrubby plant with highly variable leaf morphology that shows a considerable contrast in size and shape between the leaves of short and long shoots. These and other related taxa are often distinguished with the help of leaf shape features without mention of the short- and long-shoot leaf dimorphism found throughout much of the genus and family Rosaceae. Using both elliptic Fourier analysis and traditional morphometric shape data, we compared the short-shoot and long-shoot leaves of 59 herbarium specimens of P. microcarpa subsp. microcarpa (C.A.Mey.) Boiss. and P. microcarpa subsp. tortuosa (Boiss. & Hausskn.) Browicz collected from across the northwestern corner of the species range in Turkey. PCA of our data indicates that leaf shape is not helpful in distinguishing these two taxa, but finds significant differences between the morphometric characteristics of smaller, elliptic short-shoot and the relatively larger, ovate long-shoot leaves. We also find individuals from the same population may have very different mean leaf shapes, indicating that factors other than altitude or local climate are responsible for the variation. Our results imply a need for caution in using these features for systematic and taxonomic usage, as well as some considerations of using herbarium specimens in this type of morphometric analysis.