Within Menispermaceae, endocarp shape is highly variable and often characteristic. This study applied geometric morphometrics to the investigation of horseshoe-shaped endocarps that characterized the former Menispermeae tribe. The shape of 823 endocarp specimens, representing 66 species and 16 genera, were described on the lateral face by the means of 4 landmarks and 18 semilandmarks. The general Procrustes analysis was used to remove size and orientation of the specimens. Using thin-plate splines, we were able to visualize and describe the variation in shape for each genus and/or species. The main differences concern the symmetry/asymmetry of endocarp, the relative size of condyle, the relative length of ventral face and the concavity of ventral face. The results of a PCA reveal that for all genera except Diploclisia, generic variability is explained by a continuum in intra- and interspecific variability. Endocarp shape differed significantly between genera, demonstrating the potential for geometric morphometrics in fossil identification. Allometry explained only a small part of shape variation. Phylogenetic content is evaluated by comparing the results of cluster analysis with recent molecular phylogenies. Endocarp shape affinities appear to be quite different from phylogenetic relationships, demonstrating the low phylogenetic signal in endocarp shape at the family level. However, stronger variation is found in the lineages leading to modern genera. With a known phylogeny, geometric morphometrics is a good tool to understand shape evolution.
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Document Type: Research Article
Key Laboratory of Biodiversity and Biogeography, Kunming Institute of Botany, Chinese Academy of Sciences, No.132 Lanhei Road, Heilongtan, Kunming, Yunnan 650204, P.R. China
Publication date: 01 June 2010
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