Doctor Caroline Fromont

Candidature

Caroline FromontGraduated PhD 2017

Thesis Title

Molecular ecology, geography and species interactions of Mycopsylla insects with their bacterial endosymbionts, parasitoids and host fig trees

Research Project

Mycopsylla fici Tryon known as the fig psyllid can cause complete defoliation of its host tree, Ficus macrophylla, the Moreton bay fig, which is widely planted in parks and cities in Australia. In addition to being one of the major causes of fig defoliation, massive outbreaks of psyllids are also an aesthetic and practical disturbance as the larvae produce a sticky protecting covering or "lerp".

M. fici is involved in various species interactions. Like most sternorrhynchan insects, it harbors primary and secondary endosymbionts. Psyllids feed on a nutritionally incomplete food (plant sap); it appears that primary endosymbionts provide the missing nutrients.

Psyllid secondary endosymbionts are more diverse and their roles are mostly unknown, but some offer protection against extreme temperature or parasitoids. Parasitoids are known to commonly attack the larval stages of M. fici. In particular, females of Psyllaephagus sp. lay eggs when the lerp is closed and the development of the parasitoid larva occurs inside its host. Parasitoids emerging from the psyllid are of two different sizes and may be two different species.

M. fici and its parasitoid have been little studied. My study has two principal aims. First, the population genetics of the psyllid and its parasitoid will be studied, in order to explore and compare the geographic distribution and the population structures of two closely interacting species.

Second, I will characterise the endosymbiont flora of the psyllid and its parasitoid to uncover the diversity of primary and secondary symbionts and compare variation in the symbionts of these two species. While endosymbionts have been characterised in some psyllid species, this will be the first study on a member of the family Homotomidae.

Research Project Supervisors

Professor James Cook and A/Professor Markus Riegler

Publications

Fromont C, DeGabriel JL, Riegler M, Cook JM, (2017) 'Diversity and specificity of sap-feeding herbivores and their parasitoids on Australian fig trees', Insect Conservation and Diversity, vol.10, no.2, pp 107-119

Fromont C, Riegler M, Cook JM, (2017) 'Relative Abundance and Strain Diversity in the Bacterial Endosymbiont Community of a Sap-Feeding Insect Across Its Native and Introduced Geographic Range', Microbial Ecology, vol.74, no.3, pp 722-734

Fromont C, Riegler M, Cook JM, (2016) 'Phylogeographic analyses of bacterial endosymbionts in fig homotomids (Hemiptera: Psylloidea) reveal codiversification of both primary and secondary endosymbionts', FEMS Microbiology Ecology, vol.92, no.12, Article no. fiw205

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

Fromont C, Riegler M, Cook JM, (2015) 'Characterisation of 14 microsatellite markers for the Australian fig psylloid, Mycopsylla fici', Australian Journal of Zoology, vol.63, no.4, pp 233-235