Christopher A. Gilligan was born in Ireland and moved to England in the mid-sixties. He received his B.A. degree from Keble College, Oxford University, in 1974, and his doctorate in plant pathology from Wolfson College, Oxford, in 1978, shortly after taking up a teaching position at Cambridge in the Department of Applied Biology. Professor Gilligan has continued to work in Cambridge, moving in 1989 to the Botany School, now the Department of Plant Sciences.
Professor Gilligan’s chief distinction lies in linking epidemiological modeling and experimentation, within which he has made highly influential contributions in the theory of soilborne epidemics while also developing and testing a theoretical framework for the invasion, persistence, and variability of plant disease. Gilligan set out to develop and test a coherent theory for the dynamics and control of soilborne disease using a combination of experimentation, mathematical modeling, and statistical methods. This led him to advance the concept of the pathozone as a unifying concept to interpret the probability of infection and efficiency of control of soilborne plant pathogens around susceptible hosts. By linking the concept of the pathozone with percolation theory, derived from statistical physics, he has shown how partial control by biological or chemical methods can be used to prevent the invasion of soilborne pathogens from introduced inoculum.
Gilligan also developed and tested a theory for the dynamics of soilborne epidemics that introduced the joint dynamics of primary infection, derived from resident inoculum in soil, and secondary infection between infected and susceptible hosts. Here he showed how progress could be made in understanding and predicting the dynamics of epidemics by choosing plant components, such as roots, to represent susceptible host populations, thereby allowing for the interacting dynamics of plant growth and disease in the spread of epidemics. Using experiments on Rhizoctonia solani, Gaeumannomyces graminis, and Polymyxa betae, the vector of rhizomania disease in sugar beet, Gilligan and his collaborators have integrated the results to propose theories that scale from individual (hyphal and plant) to population (patch and field) and regional behavior. This groundbreaking work has identified the principal epidemiological mechanisms that control the dynamics of soilborne disease.
While the initial work lent heavily on nonlinear statistical methods, Professor Gilligan realized that further progress in understanding epidemics of both soil and aerial epidemics required a more rigorous mathematical treatment, not least in accounting for spatial and temporal heterogeneity. This led to a series of seminal papers and reviews that have provided a theoretical framework to understand the invasion, persistence, and variability of epidemics. Highlights include explanations for the appearance and disappearance of disease patches in successive crops, for invasion of fungicide resistance and the relationships with drug resistance, and for dynamically generated variability in which small effects early on in an epidemic become magnified. Many of the papers opened up new areas of epidemiological and mathematical study. These included methods to deal with transient behavior typical of botanical epidemics and to analyze invasion and persistence of pathogens in variable environments where there are abrupt disturbances due to sowing and harvest. Perhaps the most important advances have been in increasing our understanding of stochasticity in epidemics. While many plant pathologists focus on mean behavior, Gilligan and his collaborators designed a series of microcosm and field experiments to quantify variability within and amongst replicated epidemics. Then using stochastic, temporal or spatiotemporal epidemic models, they showed how to use limited information on variability to predict the risk of disease under different control regimes. The models have been extended to address systems as diverse as the deployment of biological control of Dutch elm disease by hypovirulent isolates of the pathogen and in identifying strategies to restrict the spread of rhizomania disease in the United Kingdom.
Though motivated by botanical epidemiology, Professor Gilligan’s research has drawn on and contributed to animal and human epidemiology. Working with colleagues in Cambridge and elsewhere, he has identified the risk of resurgence of bubonic plague in large cities as well as showing that reoccurrence of seal distemper virus in the North Sea harbor seal population results from reinvasion because the population is too small to allow seal distemper virus to persist. The work has also made wider contributions in metapopulation theory, in model simplification and in parameter estimation for temporal and spatiotemporal epidemiological models.
Now with well over 120 research papers and reviews in biological and mathematical literature, as well as an edited book, Gilligan’s research continues to evolve, tackling major new problems. Recent work has used epidemiological principles to analyze saprotrophic dynamics in soil, while collaborations with economists, together with research at the interface between population genetics, statistical physics, and epidemiology, is directed at analyzing strategies for efficient deployment of disease control in a changing agricultural landscape.
Professor Gilligan has received numerous well-deserved honors. At Cambridge, he was promoted to a personal chair as Professor of Mathematical Biology in 1999 in recognition of his work in botanical epidemiology and modeling. Receiving a personal chair and professorship is rare in the British university system, especially at Cambridge, and it is remarkable that Gilligan did this 4 years before turning 50. He became a Fellow of the Royal Statistical Society in 1995 and was awarded an Sc.D. degree from Cambridge in 1999. He holds a Professorial Fellow appointment at King’s College in Cambridge, another major honor. In 1998– 1999, he held a prestigious Royal Society Leverhulme Trust Senior Research Fellowship and served as President of the British Society for Plant Pathology (BSPP) in 2001. In 2004, he was awarded the BBSRC Professorial Research Fellowship, the only such award in all of biology in the United Kingdom. Professor Gilligan’s breadth of distinction is evident in frequent invitations to lecture for mathematics as well as biology departments and as a speaker at international conferences. He has served on numerous U.K. government committees and is in demand for national and international service. He has chaired visiting groups to assess the performance and future plans of research institutes in the United Kingdom and France and recently chaired a seminal review by BBSRC (analogous to NSF and NRI) of crop science research over the next 20 years. He is an Honorary Research Fellow of Rothamsted Research and a Director of Silsoe Research Institute and is currently a member of the Biotechnology and Biological Research Council, the principal funder of biological and agricultural research in the United Kingdom. For his many scientific and professional contributions, Professor Gilligan clearly deserves being elected as Fellow of APS.
