Combining and Comparing Morphometric Shape Descriptors with a Molecular Phylogeny: The Case of Fruit Type Evolution in Bornean Lithocarpus (Fagaceae)

Fruit type in the genus Lithocarpus (Fagaceae) includes both classic oak acorns and novel modifications. Bornean taxa with modified fruits can be separated into two sections (Synaedrys and Lithocarpus) based on subtle shape differences. Following strict criteria for homology and representation, this variation in shape can be captured and the sections distinguished using elliptic Fourier or eigenshape analysis. Phenograms of fruit shape, constructed using restricted maximum likelihood techniques and these morphometric descriptors, were incorporated into combined and comparative analyses with molecular sequence data from the internal transcribed spacer (ITS) region of the nuclear rDNA using branch-weighted matrix representation. The combined analysis strongly suggested independent derivation of the novel fruit type in the two sections from different acorn-like ancestors, while the comparative analysis indicated frequent decoupling between the molecular and morphological change as inferred...