Doctor Aidan Hall


Aidan HallGraduated PhD 2016

Thesis Title

Ecology and evolution of Cardiaspina psyllids, their bacterial endosymbionts and parasitoid wasps

Research Project

Psyllids are extremely diverse and common on Australian eucalypts and, in high densities, are capable of causing economic damage in plantations as well as dieback in woodlands. Causes of psyllid outbreaks are known to be associated with conditions of host plant stress, yet the physiological response of host plants during stress periods is poorly understood. Factors such as the interactions of psyllid endosymbionts and parasitoids during periods of outbreak are not well known.

Eucalyptus moluccana in the endangered Cumberland Plain Woodlands (CPW) throughout Western Sydney is currently experiencing massive infestations by a psyllid of the Cardiaspina genus. This infestation is unique and timely, as it can be used to decipher the factors that determine psyllid outbreaks in native woodlands. The aims of this project are to score the outbreak in an ecological context, i.e. generations per year, reproductive potential, abundance throughout the year and parasitism rates, and to relate these to temperature and rainfall. The project will also include the first comprehensive analysis of psyllid associated symbionts and the role they play in nutritional supplementation and protection against parasitoids in Australian psyllid species, with particular focus on the primary symbiont, Carsonella ruddii.


Hall AAG, Johnson SN, Cook JM, Riegler M, (2019) 'High nymphal host density and mortality negatively impact parasitoid complex during an insect herbivore outbreak', Insect Science, vol.26, no.2, pp 351-365

Hall AAG, Steinbauer MJ, Taylor GS, Johnson SN, Cook JM, Riegler M, (2017) 'Unravelling mummies: cryptic diversity, host specificity, trophic and coevolutionary interactions in psyllid - parasitoid food webs', BMC Evolutionary Biology, vol.17, no.1, pp 1-15

Morrow JL, Hall AAG, Riegler M, (2017) 'Symbionts in waiting: the dynamics of incipient endosymbiont complementation and replacement in minimal bacterial communities of psyllids', Microbiome, vol.5, Article no.58

Ryalls JMW, Moore B, Riegler M, Bromfield LM, Hall AAG, Johnson SN, (2017) 'Climate and atmospheric change impacts on sap-feeding herbivores: a mechanistic explanation based on functional groups of primary metabolites', Functional Ecology, vol.31, no.1, pp 161-171

Gherlenda AN, Esveld JL, Hall AAG, Duursma RA, Riegler M, (2016) 'Boom and bust: rapid feedback responses between insect outbreak dynamics and canopy leaf area impacted by rainfall and CO2', Global Change Biology, vol.22, no.11, pp 3632-3641

Hall AA, Morrow JL, Fromont C, Steinbauer MJ, Taylor GS, Johnson SN, Cook JM, Riegler M, (2016) 'Codivergence of the primary bacterial endosymbiont of psyllids versus host switches and replacement of their secondary bacterial endosymbionts', Environmental Microbiology, vol.18, no.8, pp 2591-2603

Hall AG, Gherlenda AN, Hasegawa S, Johnson SN, Cook JM, Riegler M, (2015) 'Anatomy of an outbreak: the biology and population dynamics of a Cardiaspina psyllid species in an endangered woodland ecosystem', Agricultural and Forest Entomology,  vol.17, no.3, pp 292-301

Steinbauer MJ, Burns AE, Hall A, Riegler M, Taylor GS, (2014) 'Nutritional enhancement of leaves by a psyllid through senescence-like processes: insect manipulation or plant defence?', Oecologia, vol.176, no.4, pp 1061-1074

Research Project Supervisors

A/Professor Markus Riegler, Dr Scott Johnson, Prof James Cook