Epicuticular wax morphology and the taxonomy of Rosa (section Caninae, subsection Rubiginosae)

Classification within the genus Rosa is problematic due to +/- continuous variation of morphological characters. The dogroses, (Rosa, section Caninae) are classified only by their unique meiotic system not by directly visible characters. The intrasectional structure remains insufficient, as the characters (glands, hairs and prickles) are known to exhibit great morphological divergence affected by both genetic plasticity and environmental influences. Taxonomy of dogroses follows a highly artificial system which allows us to identify morphospecies, which are not necessarily evolutionary species. However, SEM-studies in the Caninae revealed that all taxa of the subsection Rubiginosae are characterised by a granule type of epicuticular waxes, whereas members from the other subsections (with three exceptions) form triangular rodlets. Comparison with specimens grown under the same conditions confirmed these findings on natural populations and additionally revealed that following artificial hybridism, offspring develop the maternal type of wax structure due to the matroclinal inheritance in this section.