Corymbia torelliana hybrids for hardwood forestry - without the weediness!

Corymbia torelliana hybrids have great potential for sustainable plantation forestry in many areas of tropical Australia. The species as a parent in hybrid breeding programs confers benefits such as resistance to Ramularia shoot blight, environmental plasticity, effective site capture and good rooting ability for clonal forestry. C. torelliana occurs naturally in rainforests and rainforest margins in the wet tropics region of Far North Qld between Shiptons’ Flat, near Cooktown and Mt Fox, near Ingham. The species has a tendency to become a weed where it is planted in areas outside of the wet tropics. Consequently, it is now listed as a noxious weed by many local councils between Grafton and Mackay and there are bans on selling, propagating and distributing the species. C. torelliana has a unique seed dispersal syndrome that may contribute to its weediness in areas where it has been introduced. Seeds are dispersed by bees, sometimes up to 300 m from the parent tree (Wallace and Trueman 1995). Native stingless bees of the genus Trigona build their nests from plant resins, and T. carbonaria forages for resin inside the mature capsules of C. torelliana. When the bees forage for resin, C. torelliana seeds become attached to the resin droplets carried by bees. The bees eventually discard the seeds outside their nests. Seeds dispersed by bees are almost all viable, and abundant germination and establishment occurs around hives and wild nests. Some beekeepers claim that C. torelliana is harmful to stingless bees. Claims are that the seed “clogs” the nest and prevents bee movement, and that the resin from C. torelliana, when used in nest structures, tends to collapse, causing death of the colony. In spite of no scientific study on the weediness of C. torelliana or the effect on stingless bees, C. torelliana has been banned from new plantings and actively removed by local councils from amenity plantings. In this study, we examined the interaction between stingless bees and C. torelliana and its hybrids in the natural range of C. torelliana in the Wet Tropics . Here we report the structure of hybrid capsules and their attractiveness to stingless bees