The adaptive role of nectarial appendages in Colchicum

Abstract

Within the genus Colchicum of the Colchicaceae family, a small group of species native to the transitional belt of the Mediterranean and the Middle East deserts are characterized by unique morphological traits: nectarial appendages that occur at the base of the perianth segments and consist of two lamellae with teeth. An adaptive advantage to this unique morphological trait has yet to be presented. The morphology of the nectarial appendages was measured in three species and in a population representing a potential new species with similar traits for the first time. Nectarial appendages and nectar standing crop are larger for the inner whorl of perianth segments in all species, although the perianth segments are smaller. Intact flowers received more ant visits in outer than in inner whorl perianth nectaries although they had less nectar; removal of the nectarial appendages resulted in an opposite trend. Ant visits to flowers reduced nectar standing crop. Ant access pattern within flowers and the effect nectarial appendages had on it imply that these organs prevent ant access to nectaries. The negative effect they have on the nectar standing crop could reduce the fitness of the species assuming that ants do not pollinate. The role of nectarial appendages as nectar-theft deterrents is reinforced in light of the group’s harsh habitat and flowering season.