Recapitulating the evolution of symbioses in firebugs

• Applicant: Dr. Adam Martinez, Ph.D.
• Subject Area: Ecology and Biodiversity of Animals and Ecosystems, Organismic Interactions ; Evolution, Anthropology ; Microbial Ecology and Applied Microbiology ; Systematics and Morphology (Zoology)
• Term: from 2016 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 320419636

The ancient acquisition of nutrient-supplementing microbes by insects preceded major radiations into novel plant niches. Herbivorous bugs (stinkbugs and relatives) are often infected with gut microbiota that are essential for host nutrition. One family of bugs, the Pyrrhocoridae firebugs, evolved from Burkholderia-infected ancestors, but now typically maintain a core set of four different microbes including, Coriobacterium, Gordonibacter, Clostridium, and Klebsiella. This symbiont displacement was important for their specialization on a vitamin-limited and toxin(CPFA)-containing diet of Malvales plant seeds, but not all members maintain associations with all four bacteria. A basal pyrrhocorid species, Probergrothius angolensis, for example, feeds on the Welwitschia plant found only in the Namibian Desert and lacks Coriobacterium and Gordonibacter symbionts essential for vitamin supplementation in other firebug species. Like Malvales seeds, its diet of Welwitschia seeds also contains CPFAs and likely vitamin limited (as many seeds are), so it is unclear how P. angolensis subsists on this diet with only the Clostridium and Klebsiella symbionts. Recent phylogenetic analyses show that P. angolensis lineage likely diverged before acquisition of the other two bacteria, so studying this species may give unique insight on how symbiont acquisitions affect the ecology of their insect hosts and allow them to exploit novel ecological niches. The proposed projects aim to recapitulate the evolutionary history of the firebug symbiosis via: 1) Measuring vitamin content of Welwitschia seeds and using behavioral observations to understand the nutritional requirements of an insect representing transitional stages between symbioses. 2a) Introducing novel symbiont infections and food sources to recapitulate evolutionary processes of symbiont acquisitions. 2b) Isolation and genome sequencing of symbiotic bacteria for examination of vitamin synthesis pathways, then reinfection of P. angolensis with isolated bacteria to understand each symbionts individual contribution to host fitness. 3) Assessing potential shifts in the composition of microbial mid-gut communities among natural allopatric populations of P. angolensis feeding on Welwitschia and Malvales seeds. These projects in the lab of Dr. Martin Kaltenpoth at JGU-Mainz, Germany represent a significant departure from my pre-doctoral studies that will allow me to learn new techniques such as genome sequencing, anaerobic bacterial cultivation, phylogeny reconstructions, and chemical analytics. The addition of these skills will be of great benefit for future scientific-academic appointments.

• DFG Programme: Research Grants