Abstract
Overview: Species interactions can drive diversification. This is particularly true in cases of coevolved symbioses, where coevolutionary processes can lead to the generation and maintenance of novel functional and genetic diversity as organisms respond to each over microevolutionary timescales. Furthermore, such evolutionary coupling can lead to taxonomic diversification, as one or more partners track one another over macroevolutionary time scales. While this is widely recognized, much of the underlying diversity in such systems may be obscured without extensive sampling and taxonomic investigation. This research takes a comprehensive approach to uncover suspected hidden diversity within an iconic example of symbiotic coevolution, the fungus-growing ant symbiosis. Through broad geographic sampling, targeting taxa in which we expect to encounter cryptic species, the research team will uncover phylogenetic and taxonomic diversity of the over two hundred species of ants, their cultivated fungi, parasites that attack these fungi, and bacteria that function in garden defense and metabolic processes. Coupling metatranscriptomic and metabolomic approaches, they will characterize genetic diversity, assessing whether and how the functions of the ants' garden microbiomes complement those of the core symbionts within the system. Finally, recognizing that chemical interactions are key drivers of most species' interactions, they will use cutting-edge techniques in natural products research to discover the functional chemistry underlying symbiont communication, pathogen suppression, and mutualistic facilitation. This project benefits from the wide-ranging expertise of the US-Brazil investigative team, whose researchs pans insect and fungal taxonomy, phylogenetics, genomics, and natural products chemistry. Intellectual Merit: While profound insights into organismal evolution and diversification have been gained through the study of two-way interactions between predators and prey, between hosts and parasites, and between mutualistic partners, there is increasing recognition that such coevolutionary processes are embedded within complex ecological communities that involve other species, many of which are microbes. This complexity may lead to diffuse coevolution, where interacting species do not evolve in response only to one another but to multiple potential partners and antagonists. Assessing whether coevolution and specialization can be strictly maintained in such a context requires extensive sampling and understanding of the taxonomic, phylogenetic, and functional diversity within a system. Building on previous research in the fungus-growing ant symbiosis, this research will leverage the diversity of this tractable symbiosis to address this central question. Broader Impacts: As a textbook example of symbiosis and coevolution, the fungus-growing ant system has an extensive history of research and captivates the public. The team will take a unique approach to collaborate with a historian to document their international research and how it builds on previous research. Video interviews stemming from this collaboration will serve as the backbone of a multimedia video installation, which will be displayed at two museums and a public science festival. In Brazil, the researchers will lead a workshop for graduate and undergraduate students on microbial isolation. The project will train post docs, graduate students, and undergraduates, who will be recruited through a targeted approach to reach candidates from backgrounds underrepresented in STEM. (AU)