Pollination features and floral volatiles of Gymnospermium scipetarum (Berberidaceae)

The discovery of few isolated populations of Gymnospermium scipetarum (since now considered as an amphi-Adriatic endemic) in the S-Apennines prompted to investigate, also for conservation purposes, some aspects of its reproductive biology. We aim: (1) to determine if insects play an important role in pollination; (2) to describe the pollinator community; (3) to detect floral scent composition. Experiments of insect exclusion were carried out in the field using 24 flowering individuals: one raceme was capped whereas the nearest one was used as control to ascertain differences in seed set. Pollinator community was detected during the blooming phase of two consecutive flowering seasons by visual observation; insect identification was made at the highest possible taxonomic resolution with the help of digital photographs. In order to determine the chemical composition of the volatiles, we used SPME sampling of cultivated plants. Mann-Whitney U test reveals significant differences for treatment in mean seed set with very low values for capped flowers, thus clearly indicating as insects are crucial for successful pollination. During the 42 h of observations we detected 326 visitors belonging to only three guilds: 79% were Diptera, 20% Hymenoptera and 1% Coleoptera. We identified overall 36 floral organic compounds with only two compounds common to the other studied Berberidaceae. Ambrox was never identified before in the floral scents of any angiosperm. The presence in the scent of several aldehydes and one ketone (benzophenone) could be related to the detected dominance of muscoid flies as pollinators. Floral morphology and composition of the pollinators community indicate a generalist pollination behaviour probably related to its phenology and habitat preference. The possibility of being pollinated also by muscoid flies can be considered an advantage for the reproductive fitness of the species, since these Diptera are abundant in the mountain pastures surrounding the forest habitat of Gymnospermium.