The eastern cherry fruit fly Rhagoletis cingulata was recently introduced to Europe were it co-infests cherries with the native European cherry fruit fly Rhagoletis cerasi. The shared habitat of the two insect species resulted in the horizontal transmission of a Wolbachia strain from R. cerasi to R. cingulata. Additionally specific R. cerasi populations are infected by a Wolbachia strain that is present in R. cingulata. Thus, the two fruit fly species provide a unique opportunity to resolve the dynamics of a horizontal transfer of Wolbachia in nature.

Our research objective will be accomplished by whole genome sequencing of different Wolbachia strains to precisely characterize their identities and relatedness. We will also trace the spatial and temporal distribution of the newly acquired endosymbiont in natural populations and test for reproductive effects on their hosts through laboratory crosses. Finally, we will determine the introduction routes of R. cingulata by performing extensive genomic characterization of native and invasive fly populations. Our joint study of Wolbachia and its native and invasive Rhagoletis hosts will provide novel insights into the early stages of Wolbachia transmission, the spread of the endosymbiont in nature and the consequences of the new infection for the fly.

In cooperation with: Christian Stauffer, Boku, Vienna; Jeff Feder, University of Notre Dame, USA; Lisa Klasson, Uppsala University, Sweden

Psyllids are a small group of phloem-feeding insects that have evolved intimate associations with a variety of bacterial symbionts. These symbiotic relationships often contribute to the insect’s diet by making the nutritionally unbalanced plant sap exploitable and enabling the host to adapt to diverse ecological niches. The acquisition of essential nutrients, particularly amino acids and vitamins, through symbiotic associations is a key aspect of these interactions, influencing psyllid fitness and reproductive success. The co-evolutionary dynamics between psyllids and their symbionts have shaped the genomic structure of both parties, leading to intriguing adaptations and molecular interdependencies. However, the relationships between insects and their symbiotic partners are dynamic as symbionts can be frequently acquired, replaced, or lost. 

In this project, we aim to reconstruct the co-evolutionary history of psyllids with their symbionts and to identify events of symbiont co-diversification, losses and replacements across the psyllid tree of life. As several psyllid taxa are gall-inducers, we will also investigate how the evolution of this lifestyle has influenced their symbiont communities. We plan to determine the nutritional and protective properties of bacterial symbionts from more than hundred psyllid species by using a combination of whole genome sequencing, phylogenetic reconstructions, fluorescence microscopy, and metabolomic assays. The results of this project will not only provide new insights into the evolutionary dynamics of symbionts of this diverse group of insects, but also deepen our understanding of the evolution and dynamics of insect-microbe relationships in general.

In collaboration with: Michael Gerth, Martin Luther University of Halle-Wittenberg; Martin Kaltenpoth, Max Planck Institute for Chemical Ecology Jena; Liliya Serbina, Museum für Naturkunde Berlin

Phytoplasmas are bacteria responsible for a wide range of plant diseases. These bacteria are transmitted by sap-sucking insects, especially jumping plant lice. Apple proliferation is a phytoplasma disease of apple trees in Europe. While several different psyllids occur in apple orchards, just the two species Cacopsylla picta and Cacopsylla melanoneura are known to transmit phytoplasma with varying  transmission efficiencies among regions. Moreover, these species showed regional differences in phytoplasma transmission efficiency. 

We aim to address the question of what causes different phytoplasma transmission efficiencies. By using population genomic tools we will study the tripartite interaction between the phytoplasma, the vector, and its microbiome which will provide novel insights into the complex biology of Phytoplasma transmission.

In collaboration with: Michael Eickermann, Luxembourg Institute of Science and Technology; Wolfgang Jarausch, RLP Agroscience

A series of damaging events, such as the Vaia storm, snow pressure events, as well as the extreme drought this summer, have led to South Tyrol's forests being significantly weakened, thus causing the outbreak of the European spruce bark beetle. Especially the long heat period this year has led to the rapid development and proliferation of this secondary pest. This has led to a population outbreak never before observed in the Southern Alps. The high number of beetles means that currently not only damaged and weakened trees, but also healthy trees are attacked and killed, causing enormous economic and ecological damage. 

The project aims to investigate important aspects of the biology of this beetle in the short term in order to predict population development and to find possible antagonists that can limit its population development, to establish methods in the medium term to detect infested trees at an early stage and thus minimize population pressure, and in the long term to develop strategies to make South Tyrol's forests fit for climate change and its consequences.​​​​​​​

In cooperation with: Christian Stauffer and Martin Schebeck, Boku, Vienna; Massimo Faccoli and Andrea Battisti, Università degli Studi di Padova 

The vast ecological and economic consequences by the current bark beetles outbreak are of increasing importance in all programme regions in both countries. The two most damaging bark beetles are Ips typographus and Hylobius abietis. They are present in the whole transnational area, so a common solution would benefit not only both countries but the whole alpine area, which is currently threatened by these two pest species. The collaboration between universities and enterprises on both regions will provide a good sharing of know-how and tests in different areas, in order to define solutions that can be adopted in both sides of the alps.

Up to now there is no effective solution for the control of spruce bark beetles and pine weevils, currently the only way to reduce the population is to cut attacked trees and extract the log (or at least the bark) from the site. More effective solutions, that are technically and economically feasible, also with the contribution by private subjects, need to be explored and tested. A solution, based on natural extracts, has been tested in a pilot study showing promising results, so there is need to test and diffuse this solution in order to find the way to stop the tremendous damage caused by the bark beetles.

In cooperation with: Rigoni di Asiago; Andrea Battisti and Massimo Faccoli Università degli Studi di Padova; Martin Schebeck and  Christian Stauffer, Boku, Vienna

The olive fly, Bactrocera oleae is the most destructive pest of olives in the whole Mediterranean basin and represents the major threat to olive production worldwide. Strategies to control this pest species rely mainly on the use of conventional chemical pesticides whereas sustainable approaches are currently inefficient. Bactrocera oleae is living in close relationship with a microbial symbiont which is required for the larval development. 

In this project we test an innovative control strategy focusing on the manipulation of obligate bacterial symbionts of these pest species. Symbionts of the olive fly undergo an environmental phase, on the egg surfaces, prior to the acquisition by the newborns, becoming a good target for the application of the anti-symbiotic agents. The objective of the present project is to assess the microbial community of B. oleae and characterize the functional properties of primary symbionts using a whole genome approach. Our project will provide novel insights into the role of microorganism diversity in B. oleae fitness and to implement a novel control strategy based on symbiosis disruption.

In cooperation with: Isabel Martinez-Sanudo and Luca Mazzon Università degli Studi di Padova