President of BSPP 2001: Christopher Gilligan

The new President of BSPP, Christopher Gilligan, holds a personal chair in Mathematical Biology at Cambridge, where he has worked since 1977.  His research is centred on the use of mathematics and experimentation to unravel the dynamics of botanical epidemics. The aim is to derive and test a theory that will explain why some diseases invade and persist, while others do not, and to understand the mechanisms at a range of scales from the microscopic growth of fungal hyphae in soil, through fungal colony dynamics to the generation of disease patches and the regional spread of disease. Rather unusually for an epidemiologist, the experimental work has encompassed a range of soil-borne plant pathogens and biological control agents. Foremost amongst these are Rhizoctonia solani (mostly on radish and potato) and Trichoderma viride, Gaeumannomyces graminis on wheat and Pseudomonas spp. and more recently Meloidogyne incognita on tomato and Verticillium chlamydosporium. Many of the ideas developed and tested for these systems can be adapted for other diseases. The theoretical interests  so far  have been extended to other plant pathogens, notably Sclerotinia minor and Sporidesmium sclerotivorum on lettuce, Polymyxa betae and rhizomania disease of sugar beet, Dutch elm disease including hypovirulence, as well as to the spread of fungicide resistant parasites. The picture enlarges to consider parallels and contrasts with animal and human diseases leading to collaborative studies to analyse persistence of seal distemper virus that killed many seals in the North Sea in the 1980s (which contrasts with the persistence of Dutch elm disease) and to the historical and contemporary risk of epidemics of bubonic plague (which illustrates the effect of a reservoir of infection on disease persistence rather like saprotrophic dynamics).

Chris Gilligan - BSPP's President in 2001

Chris was educated as a biologist, first at Keble College Oxford where he graduated with a B.A. in Agricultural and Forest Science in 1974, following an early education in Ireland before moving to England in the mid sixties. The Oxford degree was broadly based, encompassing pathology, entomology, soil science, agricultural ecology, elementary statistical design and economics. Most of all, Chris asserts, the degree taught him how to think. This came mostly from one to one tutorials with gifted tutors, including Bob Lucas (a mycologist and former student of Denis Garrett) at Keble, Philip Beckett (a soil scientist), David Smith (an eminent microbial physiologist), Colyear Dawkins (forester and biometrician) and George Gradwell (an entomologist) under the guidance of John Burnett. Moving to Cambridge, a few years later, Chris concluded that Cambridge undergraduates emerged from the Natural Sciences Tripos knowing tactically more from the intensive lecture structure but with less strategic understanding. Of course, now Cambridge students  can do both! There was a mathematics option available in the first year at Oxford. Chris attended the first couple of lectures in which darkness was liberally shed on probability and he reluctantly accepted his tutor’s advice to take geology as a subsidiary. This might have been a fateful decision had it not been possible to compensate for these gaps later.

Chris stayed at Oxford for his D.Phil., moving to Wolfson College and  working on the take-all fungus under the direction of Bob Lucas, Mike Asher and John Burnett in the Department of Agricultural Science. Here that streak of independence first asserted itself and he soon began to work on systems analysis in which he broke down the components of infection and transmission into quantifiable pieces, albeit without then the necessary mathematical tools to reassemble the components. That period was one of relaxed enquiry, as Chris first began to think seriously about an academic career while settled into married life with Joan, interrupting their impecunious honeymoon in Oxford to set up an inoculum density-disease experiment. The sun always shone and never more so than in 1976, when Chris caught heat-stroke doing field work on take-all at Wytham and began to have a glimmering that he might become a theoretician.

Towards the end of his graduate work, Chris applied for several jobs in plant pathology that included a lectureship in Papua New Guinea, advisory work with ADAS,  a post in a chemical company and a job at Cambridge. This was a pivotal point in his career and he went to Cambridge intending to stay only for five years. The job, ingloriously called a University Demonstratorship, (the equivalent post in the arts and humanities was called an Assistant Lectureship) involved lecturing and demonstrating in Plant Pathology, Plant Breeding and Biometry in the Department of Applied Biology. This required some urgent self-improvement in plant breeding and biometry, and in plant pathology too. A quest to improve his statistical education led to evening classes at Cambridgeshire College of Arts & Technology in statistics and probability.  Amongst the tutors was Anne Campbell now the MP for Cambridge with whom Chris later published a paper on simulation. To his disappointment, however, Anne was unwilling to put the Houses of Parliament as her current address, fearing, groundlessly, that her tenure there might be rather short.

During this time, other papers began to appear, the first being a Letter to the Editor of Phytopathology, entitled Modelling of Rhizosphere Infection that incited a spirited series of responses and a referee’s report from Ralph (Tex) Baker that was longer than the original paper. The scientific discourse with Tex continued, leading to an idyllic family sabbatical in Colorado in 1982, accompanied by Joan and their first two children Clare and Richard. Chris was promoted to a tenured lectureship while on leave: rhizosphere infection matured into the ideas of pathozone infection and later dynamics and Chris returned to Cambridge to teach Epidemiology and Plant Pathology in collaboration with David Ingram in the Botany School and a new course in Sampling and Spatial Analysis. Denis Garrett had retired by the time Chris arrived in Cambridge but they met occasionally, while John Rishbeth continued to lecture in the Botany School. The research now began to take on a more statistical flavour with papers on aerial and soil-borne pathogens. Towards the end of the 1980s the experimental work moved back into the soil with the arrival of Rik Werker, Phil Brassett, Sarah Simons and Sarah Blunt as graduate students – and coincidentally the birth of Chris’ second and third daughters, Helen and Elizabeth. Chris was elected to a Fellowship at King’s College and began to balance more teaching with research and administration, becoming Director of Studies for Natural Sciences, which includes the physical as well as biological sciences, with the usual demands of six hours tutorial teaching a week. Busy though it seemed, the load now appears attractive compared with current demands. For a time, Chris worked on spatial analysis, then very much in vogue in the U.S., but while he felt that the initial work in the U.S. was innovative, the statistical techniques could do little more than describe disease. Further progress in understanding epidemics needed more attention to the underlying temporal and spatial dynamics. This in turn demanded more mathematical insight and during the early 1990s, having moved following a rather painful closure of Applied Biology, to the Botany School now renamed Department of Plant Sciences, Chris took time to learn more mathematics. It was a calculated risk. It slowed research output for a time. Along with the work of others, however, it opened up botanical epidemiology to the broader arena of animal and human epidemiology. At the same time, Chris devised a 60 lecture course in mathematical biology, taken by first year biologists with one or more A levels in  maths at Cambridge. This began  a transition from teaching and research in biology to mathematical biology with the course now attracting 200 students a year. The research group began to grow as mathematicians and physicists joined experimenters. Key arrivals in the group included Doug Bailey to work on the pathozone, disease dynamics and host growth; Wilfred Otten to work on soil physics and fungal growth; Chris Thornton to develop and use immunological methods for quantification in collaboration with Molly Dewey at Oxford. The theoretical output was expanded by Adam Kleczkowski, who initiated work with Chris and the experimenters on scaling-up from individual to population behaviour in relation to biological control. Simon Gubbins arrived to work with Chris on biological control and more recently fungicide resistance while Adrian Stacey, Cerian Webb and James Truscott have begun to explore hyphal and mycelial growth in disease transmission though to the  regional and spatial spread of disease and its relationship with host growth. Broader epidemiological work has come from joint work with Jonathan Swinton and Matt Keeling from the Department of Zoology.

The approach of the epidemiological research is different from most others in that the group focuses on understanding the underlying population dynamics upon which the environmental variation acts. A current theme of the work is to analyse why epidemics differ, and how small changes in dynamics become amplified. Significant progress has been made in this by recent collaborations with Gavin Gibson at Edinburgh. Perhaps the most significant feature of the work is the close interaction between experimentation and theory with mathematicians and experimenters working alongside each other in the same laboratory. When funding permits, the modal size of the Epidemiology and Modelling Group is a little over 15. Four more research fellows are currently supported in the King’s College Research Centre, established by Chris and others, on a related mathematical project on so called spatially-extended dynamics that looks at how diseased populations interact.

The 1990s closed with a Royal Society, Leverhulme Trust Senior Research Fellowship that freed Chris from teaching for a year to concentrate on research, together with a professorship and an Sc.D. from Cambridge, and vice-presidency of the BSPP, all of which he says though very pleasant and not a little surprising made him feel old! Even so there is still so much to do. With 20 years to go before official retirement, where would Chris like the research to go? Many possibilities compete but major challenges lie in the interface between epidemiology and genetics and in the comparisons between animal and plant epidemiology, while the mathematics of molecular and developmental biology also beckon but only if there are tractable experimental systems to test the models. Time, however, remains the challenge in balancing research with the demands of administration and teaching, a feature that may emerge during the coming year.

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