Thrips (Thysanoptera) pollination in Australian subtropical rainforests, with particular reference to pollination of Wilkiea huegeliana (Monimiaceae)

Abstract

Approximately 23 species of thrips were recorded from flowers of 26 species of Australian subtropical rainforest trees, shrubs and vines (in 17 families) in the Manning Valley, coastal northern New South Wales. Pollination by thrips (thripophily) appears more widespread in rainforest communities than has been previously recognized. The pollination ecology of Wilkiea huegeliana (Monimiaceae) was studied in detail. Wilkiea huegeliana is a small, unisexual, annually flowering tree or shrub of rainforest and associated ecotones in eastern Australia, and is a larval food plant for the Regent Skipper butterfly Euschemon rafflesia rafflesia (Hesperiidae). At this latitude W. huegeliana is pollinated solely by a species of thrips, Thrips setipennis, but T. setipennis is not restricted to W. huegeliana and was recorded from flowers of 13 rainforest plant species. It appears to be the obligate pollinator also for Rapanea howittiana and R. variabilis (Myrsinaceae). Pollinator exclusion experiments were inconclusive but W. huegeliana may be facultatively agamospermous. The recruitment pathway to unrewarding female W. huegeliana flowers is uncertain but attraction may function by automimicry. Both male and female flowers serve as brood sites for T. setipennis larvae. Although the pollination ecology of W. huegeliana is specialized, the family Monimiaceae exhibits a broad diversity of pollination strategies. A number of these are discussed. The apparent obligate and restricted pollinator requirements of W. huegeliana may make it, and any associated phytophagous fauna, vulnerable to the impacts of habitat fragmentation.