International Association for Lichenology

John W. Thomson

John W. Thomson

For 50 years, North American lichenology and the name, John W. Thomson, have been almost synonymous. Starting modestly with treatments of Cladonia and Peltigera for his home state of Wisconsin in America’s midwest, John Thomson has steadily built up his knowledge of the lichens of North America, and shared that knowledge through his many articles, monographs and books, now numbering close to 100.

Although John Thomson is as American a lichenologist as anyone can imagine, one may find it surprising that Grummann’s book of biographies includes John among the lichenologists of Great Britain. John was, in fact, born in Cockenzie, Scotland, but you won’t find a trace of Scottish in his accent, long since lost after arriving in North America as a youngster. John earned his bachelor’s degree in 1935 from Columbia University, and then went to Wisconsin for his master’s and doctoral degrees, the latter being conferred in 1939.

Lichenologists in North America sometimes feel a bit lonely … after all, there are more people working on lichens in Lund, for example, than in all of Canada… but try to imagine what it must have been like back in 1935 when John began his studies of lichens, or in 1944, when he took up a position in the Botany Department at the University of Wisconsin (a position he retained, by the way, until his retirement in 1987). There was only A.W.C.T. Herre, Carol Dodge, Alexander Evans, and perhaps a few others. Even Raymond Torrey, an early correspondent of John’s, passed away in 1938. Impressed more by the opportunities to make real progress than discouraged by the lack of colleagues on the continent, John taught himself every kind of lichen from the smallest crust to the leafiest Peltigera. With John fast becoming known as the expert on lichens, he was naturally deluged with specimens for identification, sent to him for the most part by ecologists, naturalists and amateurs. I think it is fair to say that without his invaluable help during that period, lichens would have been virtually forgotten as an element of the North American flora. And he is still providing this service. The more lichens he named, of course, the more he got, and as a result, John has built the University of Wisconsin lichen herbarium into one of the largest and most important lichen collections on the continent.

John’s impact on North American lichenology can be seen in the number of North American monographs and revisions he has produced over the years: Peltigera, Cladonia, Physcia in the broad sense, Baeomyces, Rhizocarpon, Dactylina, Catapyrenium, and, most recently, Staurothele. His monographs and shorter papers often include detailed dot maps showing the North American distributions of the lichens, and these have been enormously helpful to anyone interested in the phytogeography of American species.

To a significant extent, our floristic knowledge of American lichens has been built upon John Thomson’s many authoritative reports of the lichens collected on the yearly forays of the American Bryological and Lichenological Society, often providing the first and, in some cases, still our only knowledge of the lichens in some parts of the continent. These reports cover areas in Oklahoma, Pennsylvania, northern Minnesota, California, Indiana, the Adirondacks of New York, and Washington. Some of the larger collections sent to him for determination, especially by the Canadian ecologist George Scotter, led to other significant floristic papers.

Beginning in the mid-50s, John contributed tremendously to our knowledge of the lichens of the American arctic, first dealing with the Hudson Bay region and the Canadian Eastern Arctic; and later, treating the lichens collected on numerous northern expeditions. This interest grew as John found opportunities to go north himself and sample firsthand the lichenological riches of that still underexplored land. These collecting trips have resulted in landmark books, first his lichen flora of the Alaskan Arctic Slope, and then an award-winning volume on the macrolichens of the entire American Arctic. We all await anxiously the appearance of the second volume, on the crustose species, due to be published next year.

John Thomson has been a teacher all his life, and has influenced a large number of people with his enthusiasm for lichens, as well as his warmth and generosity. He is always happy to share his knowledge with amateurs and professionals alike. Among his many students were Mason Hale and Bill Culberson who, themselves, have made a significant impact on North American lichenology. We all owe a great deal to John Thomson, and it is very fitting that he is among the first to receive an Acharius Medal.

Irwin M. Brodo