Format: ORAL

Martin Xanthos1, Isabel Larridon1,2, Simon J. Mayo1

1 Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3AE, UK 2 Ghent University, Department of Biology, Systematic and Evolutionary Botany Lab, K.L. Ledeganckstraat 35, 9000 Gent, Belgium

The Cyperus margaritaceus-niveus complex (Cyperaceae) is a group of ten tropical species (C. karlschumanii, C. kibweanus, C. ledermannii, C. margaritaceus, C. niveus, C. nduru, C. obtusiflorus,C. somaliensis, C, sphaerocephalusC. tisserantii) from sub-Saharan Africa Madagascar united by the combination of a capitate inflorescence, white-yellow glumes and swollen bulb-like bases. Recent molecular studies in the C4 Cyperus clade, have shown that some members of the complex form a monophyletic group sister to the rest of the C4 Cyperus species, however regional floras have been unable to reach a consensus on inter-species relationships, presenting differing opinions on the circumscriptions of these taxa. In this study, we use multivariate morphometric analyses - Principal Component Analysis (PCA), Linear Discriminant Analysis (LDA) and Classification and Regression Tree Analysis (CART) - to test the robustness of the species circumscriptions presented in these floras. Unlike flora accounts which only use a partial subset of the taxa, we use all species represented in the complex from across their entire geographical range. Cyperus kibweanus was not considered due to lack of material. The analyses show that eight morphospecies are recognised for the LDA, and six morphospecies are recognised for CART. Both PCA and LDA showed varying degrees of overlap in nine of the ten taxa, with no single group clearly separating in multivariate space.Notable results include: 1) the LDA cross-validation showing C. margaritaceus to form a robust entity despite its overlapping with the other taxa, and 2) the failure of C. niveus to form a distinct entity in both LDA cross-validation and CART. The computational approach attempted here is a useful tool to add to traditional taxonomic methods in resolving other species complexes in the Cyperaceae.