Urbanisation and environmental modification as drivers of insect community diversity and composition in Sydney, Australia

Abstract

Insects are essential for the functioning of ecosystems, delivering key ecological functions. Biodiversity increases the multi-functionality and resilience of ecosystems, especially under the light of global. With urbanisation, ecosystems are modified, affecting biodiversity and jeopardising ecosystems. The main objective of this research project was to investigate how insect communities are affected by urbanisation. The research project is divided in two questions: 1) Are insect communities affected by coarse or fine scale environmental filters? and 2) Are insects’ foraging abilities affected by environmental modification? To address the first question, I sampled four insect taxa in 19 sites with three levels of environmental modification, and multiple environmental variables associated with urbanisation. For the second, I used focal plants to sample floral visitors in 19 sites with varying levels of environmental modification, recording the time taken for the focal plant to be discovered by an insect, and the number of insects after 48 hours. My results show that coarse environmental filters affect Hemiptera communities but not the other groups. Fine environmental are associated with species richness of coleopteran, dipteran and hymenopteran communities. The number of insects was higher in sites with higher environmental modification, but floral discoverability was not different. Native floral resources are important for urban biodiversity. Low species richness of hymenopterans and coleopterans in more urbanised sites indicates the susceptibility of these groups to urbanisation. Environmental modification affects insects’ ability to discover and use floral resources. Where conservation initiatives use floral resource plantings to support biodiversity, environmental modification must be considered, to ensure that target taxa are able to reach the novel resources.