Mercedes Pascual is a Professor of Biology and Environmental Studies at New York University, and an external faculty of the Santa Fe Institute. Dr. Pascual is a theoretical ecologist interested in the population dynamics of infectious diseases, their response to changing environments and their interplay with pathogen diversity. She is also interested in the structure and dynamics of large interaction networks in ecology and epidemiology. Dr. Pascual received her Ph.D. degree from the joint program of the Woods Hole Oceanographic Institution and the Massachusetts Institute of Technology. She was awarded a U.S. Department of Energy Alexander Hollaender Distinguished Postdoctoral Fellowship for studies at Princeton University, and a Centennial Fellowship in the area of Global and Complex Systems by the James S. McDonnell Foundation for her research at the University of Michigan. She received the Robert H. MacArthur award from the Ecological Society of America. She is a fellow of the American Association for the Advancement of Science and a member of the American Academy of Arts and Sciences.


Abstract:

How important are specific ecological interactions to the assembly of a diverse community of species? Can coexistence reflect instead neutral assembly, simply resulting from stochastic birth-death processes? What signatures in macroscopic diversity patterns can help us distinguish among these two explanations? These long-standing questions from Ecology and its interplay with Evolution, can be similarly asked at a different level of biological organization for strain diversity within a pathogen population. I do so here for the hyper-diverse malaria parasite Plasmodium falciparum in high-transmission regions. Strains compete for hosts as these acquire specific immune memory, which creates an advantage of the rare and a disadvantage of the common, resulting in negative frequency-dependent selection (NFDS). I show that networks describing patterns of limiting similarity can help us identify the importance of this non-neutral process to coexistence. With a more analytically tractable PDE model, I further discuss implications of the positive feedback between diversity and transmission/competition intensity for resilience of the pathogen population. I end with brief mention of other microbial populations of large diversity under NFDS, and of other ecological systems to which similar ideas may apply.


The colloquium will be livestreamed at: www.ictp.it/livestream

Refreshments will be served on the terrace of the Leonardo Building after the talk (if weather permits).