Thrips and Weevils as Dual, Specialist Pollinators of the Australian CycadMacrozamia communis(Zamiaceae)

Specialist beetles (Insecta, Coleoptera) have generally been considered to be the sole pollinators of cycads that have been studied. The possible pollination role of members of the thrips genus Cycadothrips (Thysanoptera, Aeolothripidae) found on male and female cones of some species of the Australian cycad genus Macrozamia (Zamiaceae), however, has never been experimentally investigated. This study, which included behavioral observations, visitation rates, pollen loads and exclusion experiments of insect visitors to Macrozamia communis cones in New South Wales, indicated that both Cycadothrips chadwicki Mound and Tranes lyterioides (Pascoe) (Coleoptera, Curculionidae) affect pollination. This is the first demonstration that specialist pollinators of two different insect orders pollinate a cycad. Cycadothrips adults and larvae fed on pollen, and Tranes weevil adults fed mainly on male sporophyll tissue and some pollen. Larvae of both insects developed in male cones; thrips larvae fed on pollen and weevil larvae fed on cone rachis tissue. Tranes adults moved from male cones mainly during the early evening to other cones, including female cones; sometimes this occurred as a mass, synchronized movement of all adults from male cones. Thrips moved out of male cones to other cones, including to female cones, only during the daylight hours, primarily between 1200 and 1700 hours. The behaviors of other insect visitors to male and female cones suggest that they are not pollinators. The implications of Cycadothrips species as pollinators of cycads are discussed.