Exhausting all avenues: the ecological effects of roads and air pollution on biota

Abstract

Roads are a dominant and ecologically harmful feature of our contemporary urban landscape. Among their impacts vehicle collision is particularly well documented. Additional factors such as traffic-related air pollution may also have individual and population level effects; however, their impact on biota is largely unknown. In this thesis, I examined responses of invertebrates, and more specifically, the honey bee, Apis mellifera to roads and traffic-related air pollutants. I used manipulative laboratory experiments and mensurative field studies to examine responses across several levels of biological organisation. Firstly, using olfactory conditioning, I demonstrated direct and indirect effects of traffic-related air pollution on A. mellifera cognition. Bees showed reduced olfactory learning and memory following acute diesel pollution exposure. Furthermore, bees conditioned using scents degraded by petrol pollution had impaired olfactory learning, memory and discrimination. I then investigated effects of urban features including roads on trait asymmetry, an index of environmentally induced developmental stability. Specifically, I explored associations between A. mellifera wing asymmetry, and landscape traits including road, anthropogenic land and vegetation density at coarse and fine spatial scales. At coarse scales, road proximity increased asymmetry, and at fine scales, road proximity, anthropogenic land and vegetation area influenced asymmetry. Finally, I quantified arthropod diversity in roadside greenspaces and determined if habitat complexity was an important trait influencing composition. I found compositional differences between roadside and park greenspaces but no effect of habitat complexity. My results demonstrate roads and traffic-related air pollution impact invertebrates at a combination of spatial scales and levels of biological organisation. My research approach highlights the importance of understanding mechanisms, a factor critical to conservation.