Extreme floral complexity and pollination in asclepiads

The extreme complexity of asclepiad flowers (Asclepiadoideae–Apocynaceae) has generated much interest in the pollination biology of this group of plants. Wiemer et al. study pollination mechanisms and pollinators of two South American species, Morrenia odorata and M. brachystephana. The detailed structure of the flowers reveals a complex system of guide rails and chambers precisely arranged in order to achieve effective pollinaria transport, with wasps being the main pollinators. A putative new function of nectar, as a lubricant for pollinaria entering the guide rail, is suggested.