Thrips pollination of the central Australian cycad, Macrozamia macdonnellii (Cycadales)

Macrozamia macdonnellii (Zamiaceae) grows at a few isolated sites in centra l Australia. Male cones support large populations of a host-specific thrips , Cycadothrips albrechti n. sp. (Thysanoptera, Aeolothripidae). This insect breeds only in these male cones, from which the adults swarm in late after noon as the temperature falls and humidity rises. A small sticky trap at on e female cone caught 3844 adults on a single afternoon; large numbers of th rips were observed entering this cone. Each thrips carried an average of 15 pollen grains, and pollen delivery into the cone was thus estimated to ave rage more than 5500 grains per ovule. No other potential pollinators were f ound on these cycads, and it is concluded that C. albrechti is the sole pol linator of M. macdonnellii. Since Cycadothrips constitutes a basal clade wi thin the Thysanoptera, the possibility is considered that thrips were invol ved in pollen transfer before the radiation of flowering plants.