Applications of the Hertzsprung-Russell star chart to ecology: reflections on the 21(st) birthday of Geographical Ecology.

Robert MacArthur's Geographical Ecology turned 21 last year. As it enters adulthood, we may ask whether or not it is still influencing contemporary approaches to ecology. The opening sentence, 'To do science is to search for repeated patterns, not simply to accumulate facts...', is a theme of the entire book. As ecologists, we are faced with the problem of finding patterns when there is a large number of species, an even larger number of possible pairwise interactions, and when these are dispersed across a bewildering array of habitat types. How do we look for general patterns in nature? The Hertzsprung-Russell star diagram provides an inspiring example for meeting MacArthur's challenge.