Evidence of pollination by sexual deception in the endangered spider orchid Calandenia Williamsiae

Caladenia williamsiae is a morphologically unusual spider orchid restricted to a small number of populations in the western and southern wheatbelt. Here, I present evidence that C. williamsiae is pollinated by sexual deception of the wasp Aeolothynnus innocuus (Thynninae), a member of a genus not previously known to be involved in pollination of Caladenia in Western Australia. While pollen deposition was not observed, members of this wasp species were the only visitors to flowers and some individuals carried pollen of C. williamsiae. Further, all individuals exhibited the sterotyped behaviour associated with sexually deceived thynnine wasp pollinators, in many cases attempting copulation with the flower. Floral dissections showed that the sexual attractant is produced both from the labellum and terminal osmophores on the sepal