Epidendrum L. is the largest genus of Orchidaceae in the Neotropical region, with about 1,125 species. The extensive variation that is present in several species turns the delimitation of the genus and of some species a quite controversial theme. Epidendrum secundum and E. denticulatum belong to section Amphyglottium, which embraces some of the most variable species within the genus. Apart the inclusion of Epidendrum secundum and E. denticulatum in different subsections, due to the contrasting morphology of the lip callus, these species have several similarities, in the habit, morphology and flower color. As in many herbarium specimens the visualization of the lip callus is difficult; the overall similarity between the species has caused several misidentifications in herbaria as well as in living plants. The aim of this work is to select new characters set to be used for a more accurate identification of the herbarium registers of E. secundum and E. denticulatum. Thirty individuals of E. secundum and 26 of E. denticulatum maintained under cultivation in the orchids collection of the Institute of Botany of São Paulo were sampled, and 20 quantitative characters were measured from them. Methods of multivariate analysis (PCA, UPGMA, DA and Box-Plot) and Student's t Test, corrected by the Bonferroni criterion, were employed. Six floral characters have a significant difference between E. secundum and E. denticulatum, showing that morphometric techniques can be useful for the delimitation of variable species. An identification key is presented for E. secundum and E. denticulatum.
Morphological variation; morphometry; multivariate analysis; taxonomy
