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Project: 266/2008

Title: Pollination biology of the sexually deceptive threatened orchids Caladenia richardsiorum, Caladenia hastata and its pollinator Catocheilus caelebs.
Applicant: Kate Vlcek (Threatened Species Project Officer, Department of Sustainability and Environment, Victoria (Warrnambool) and Dr. Graham Brown

This project investigates the biology and behavior of the pollinators of two threatened orchids; Mellblom’s spider-orchid, Caladenia hastata, from south-western Victoria and the morphologically similar Little Dip Spider Orchid, Caladenia richardsiorum, from south-eastern South Australia.

The pollinators of both are thought to be male flower wasps (Thynnidae: Thynninae) although currently only the pollinator of Caladenia hastata is known following its discovery in 2008. What little is known or assumed about the biology of this large group of wasps is based on only a handful of species.

Observing and understanding the meteorological and environmental conditions in which the wasps are active may prove to be crucial to managing these orchids. Factors to be studied to assess wasp activity and therefore pollination success include temperature, humidity, air pressure, cloud cover, rainfall, food sources and larval hosts. Observing the interaction between the wasp and different flowers and flower parts may also reveal additional factors that may affect pollination success.

The results of this study are likely to have implications for other threatened orchids that have specific wasp pollinators.