Pollinators in seed orchards of Eucalyptus nitens (Myrtaceae)

Abstract

Flowers of the commercially important tree Eucalyptus nitens (Deane & Maiden) Maiden were visited by a diverse array of insects, but not by birds, in Tasmanian seed orchards. Most species of insects that visited the flowers of E. nitens are likely to be effective pollinators because all common species of visitors carried many grains of Eucalyptus pollen, and the open floral structure facilitates frequent insect contact with stigmas. Seed production also suggested that a wide variety of insects were effective pollinators because flowers were consistently well pollinated, despite differences in flower-visitor communities among orchards and particular branches of flowers. The generalised entomophilous pollination system of E. nitens suggests that effective pollinators should occur in seed orchards of this tree throughout the world, provided that flowering occurs at a time of year conducive to insect activity. Although a wide variety of insects appear to be effective pollinators of E. nitens, introduced honeybees, Apis mellifera L., that are often deployed as pollinators in seed orchards were consistently not attracted to the flowers. The reliance on wild insects as pollinators suggests that seed production in E. nitens may benefit from reduced use of broad-spectrum insecticides in, and near, seed orchards.