Restoration actions promoting insect pollinators and parasitoids in an endangered urban ecosystem

Restoration of endangered ecological communities is vital to conserve and expand what remains. Restoration actions need to support ecological functions vital for their long-term survival. Insects provide important ecological functions such as pollination and pest control. These insects need to be present to ensure the ecological functions are being accomplished. Our research seeks to determine if different restoration actions impact the presence and abundance of native bee pollinators.

Bee hotels are artificial structures designed to offer nesting opportunities to cavity nesting bees. Thirty four bee hotels have been deployed at 17 sites in the Australian endangered ecological community; the Cumberland Plain Woodland. Sites represent a restoration action used in combination with cattle exclusion fencing: active replanting (4 sites), passive natural regeneration (7 sites), and weeding (6 sites). They were deployed from Spring 2022 to June 2023.

Cavity nesting bees were only found in bee hotels in weeded sites. The only species nesting was Hylaeus nubilosus. However, the bee hotels were home to 9 different species of parasitoid wasps across all treatment methods over the entire study period. The prey in the bee hotels after they had emerged included Hymenoptera and Arachnids.

Despite low occurrences of native cavity nesting bees in bee hotels, other ongoing floral visitor sampling has revealed that they, and other native bees, are present in other treatment methods. However, bee hotel occupation indicates all restoration methods are supporting a high abundance of parasitoid wasps, a functional group vital for community persistence and ecosystem integrity.