Pollen morphology of the endemic genera of the Madeira archipelago, Portugal

Abstract

This study presents the first palynological characterisation of the five endemic plant genera of the Madeira archipelago: Chamaemeles Lindl, Melanoselinum Hoffm., Monizia Lowe, Musschia Dumort and Sinapidendron Lowe. Pollen grain morphology of ten endemic species was studied using light and scanning electron microscopy techniques. The size and shape of pollen grains, the polar axis, the equatorial diameter, and the exine ornamentation were measured and described. We found that the pollen grains of the five endemic genera are all medium-size monads. The close relative apiaceous Melanoselinum and Monizia differ in polar (P) and equatorial (E) diameter size and exine ornamentation while Sinapidendron species show differences in P, E, and P/E ratios. The pollen grains of the two Musschia species are very similar to each other, but differ in morphology and ornamentation from the Macaronesian endemic bellflowers Azorina vidalii and Canarina canariensis. This study unveiled differences between the endemic taxa and with their close related species, thus providing support to previous taxonomic findings.