Impacts of climate change on plant-insect interactions

Current and future climate change will have profound impacts on species interactions and communities. This thesis investigates the community structure and composition of insect communities on Australian native plant species, with the ultimate aim of predicting possible impacts of climate change. To this end, three topics were investigated: firstly the Coleoptera and Hemiptera fauna associated with several host plant species from three important Australian plant families were assessed across the plant species' native range, in terms of morphospecies composition and feeding guild structure. Secondly, possible impacts of climate change on these communities were investigated using a multispecies transplant experiment, in which plants were planted into sites that are approximately 3°C warmer, in terms of mean annual temperature. Thirdly, levels of total leaf herbivory and damage types were assessed on plant species, both across the current range and within the transplant experiment. Assessments of the Coleoptera and Hemiptera fauna across the plant species native range revealed little commonality, in terms of morphospecies composition and feeding guild structure, among plant species within each family. This was reflected by herbivory patterns, which were species-specific and characterised by changes in dominant feeding types among plant species. The assessment of potential impacts of a warmer climate on these plant-insect communities via the transplant experiment showed that for each individual plant species, Coleoptera and Hemiptera community composition may undergo significant turnover, whereas herbivore feeding guild structure may remain relatively unchanged. This relative stability between host plants and their phytophagous guilds was reflected by largely consistent patterns of leaf herbivory between native and warmer sites. We conclude that transplant experiments provide a powerful means of exploring the impacts on natural systems of a rapidly changing climate.