Indigenous plants and native bees - some research findings

29th October 2023
By Monique Burns

Monique Burns undertook her honours year for a Bachelor of Science in 2022, majoring in Ecology and Evolutionary Biology.

As part of my Honours project at the University of Melbourne, my supervisors, Dr Julian Brown and Prof. Nicholas Williams, and I found that indigenous understorey plantings support a greater diversity of native bees compared to exotic plantings.

During the spring and summer of 2021-22, we surveyed the bee communities at 32 exotic and indigenous plantings around Melbourne. To control for other factors in our study, both indigenous and exotic sites also varied in landscape context, planting size and plant species richness. One of our indigenous sites was located along the Merri Creek at Merri Murnong, Coburg, where a variety of bee-attracting plants can be found, including Chrysocephalum, Geranium and Wahlenbergia species.

We found that indigenous plantings tended to attract a greater number of bee species compared to exotic plantings. Bee communities also varied more between indigenous plantings than between exotic plantings. Altogether, this demonstrated the increased diversity of bees that can be supported by locally native plants. Several native bees were also found to be strongly associated with indigenous plantings, including Hylaeus quadriceps which specialises on Wahlenbergia. In contrast, only the European Honeybee, Apis mellifera, and no native bees, were strongly associated with exotic plantings.

Particular plant species were found to be highly effective at attracting a diversity of native bees. Wahlenbergia, also known as the Native bluebell, was one such plant. In total, 19 different bee species were observed on Wahlenbergia capillaris over the course of the survey period. This contrasted with exotics, such as Gazania, which hosted five different bee species, two of which were exotic: the European Honeybee and the African Carder Bee.

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Lasioglossum (Chilalictus) sp. on Native bluebell, Wahlenbergia; Speedwell, Veronica perfoliata.

Plants of the family Myrtaceae, including Eucalyptus, Callistemon and Leptospermum, were also found to be important for native bees. Flowers of these plants are generally shallow and have an open shape, allowing a diversity of bees to access the nectar within. Furthermore, many bees, often those of the ancient bee family Colletidae, are Myrtaceae-specialists, meaning they feed predominantly on these plants and would not occur in a landscape without them.

Bees provide the crucial ecosystem service of pollination, but many scientists fear a drastic decline resulting from parasites, pesticide use, habitat loss and climate change. We hope that this research demonstrates the potential for urban areas to support native bees and encourages Melbourne residents and councils to grow indigenous plants in their backyards and public green spaces.

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Lasioglossum (Chilalictus) sp. on Geranium, Geranium

Images: Monique Burns

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