Pollen morphology of Croton sect. Lamprocroton (Müll. Arg.) Pax (Euphorbiaceae) and its taxonomic implications

A palynological analysis of 22 taxa of Croton sect. Lamprocroton (Müll. Arg.) Pax was accomplished in order to obtain evidence for a good interspecific delimitation and phylogenetic characterization of this group. Samples of 22 taxa (from which approximately 90% of the species belonged to this section) were obtained from herbarium specimens; moreover, pollen grains were analyzed with light and scanning electron microscopy. Characters observed from pollen grain diameter and from exine ornamentation were registered and compared. Pollen grains were found to be spherical, apolar, inaperturate and with a diameter ranging from 49.32±0.94 μm in C. ehrenbergii Schltdl. to 86.42±1.33 μm in C. muellerianus L. R. Lima . Pollen morphology of three recently described species of Croton was analyzed for the first time herein. In addition the results of this study confirm the distinctness of these species but do not support a recently proposed new variety of C. pallidulus Baill.