Background

Robert Macarthur was born on April 7, 1930 in Toronto, Canada, into the family of John Wood and Olive (Turner) MacArthur. While MacArthur spent his first seventeen years in Toronto, his father shuttled between the University of Toronto and Marlboro College in Marlboro, Vermont, as a professor of genetics.

Education

MacArthur received his Bachelor's degree in mathematics from Marlboro College, followed by a Master's degree in mathematics from Brown University in 1953. A student of G. Evelyn Hutchinson, MacArthur earned his Ph.D. from Yale University in 1957; his thesis was on the division of ecological niches among five warbler species in the conifer forests of Maine and Vermont.

Career

Upon receiving his doctorate in 1957 from Yale University under the direction of G. Evelyn Hutchinson, MacArthur headed for England to spend the following year practicing ornithology with David Lack at Oxford University. When he returned to the United States in 1958, he was appointed an assistant professor of biology at the University of Pennsylvania.

As a doctoral student at Yale, MacArthur had already proposed an ecological theory that encompassed both his background as a mathematician and his growing knowledge as a naturalist. While at Pennsylvania, MacArthur developed a new approach to the frequency distribution of species. One of the problems confronting ecologists is measuring the numbers of a specific species within a geographic area — one cannot just assume that three crows in a ten-acre corn field means that in a one thousand-acre field there will be three hundred crows. Much depends on the number of species occupying a habitat, species competition within the habitat, food supply, and other factors. By taking the sum of the product of the frequencies of occurrences of a species and the logarithms of the frequencies, complex data could be addressed more easily.

The most well-known theory of frequency distribution MacArthur proposed in the late 1950s is the so-called broken stick model. This model had been suggested by MacArthur as one of three competing models of frequency distribution. He proposed that competing species divide up available habitat in a random fashion and without overlap, like the segments of a broken stick. In the 1960s MacArthur noted that the theory was obsolete. The procedure of using competing explanations and theories simultaneously and comparing results, rather than relying on a single hypothesis, was also characteristic of MacArthur’s later work.

In 1958 MacArthur initiated a detailed study of warblers in which he analyzed their niche division, or the way in which the different species will specialize to be best suited for a narrow ecological role in their common habitat. In the 1960s he studied the so-called “species-packing problem.” Different kinds of habitat support widely different numbers of species. A tropical rain forest habitat, for instance, supports a great many species, while arctic tundra supports relatively few.

The book The Theory of Island Biogeography, written with biodiversity expert Edward O. Wilson and published in 1967, applied these and other ideas to isolated habitats such as islands. The authors explained the species-packing problem in an evolutionary light, as an equilibrium between the rates at which new species arrive or develop and the extinction rates of species already present. These rates vary with the size of the habitat and its distance from other habitats.

In 1965 MacArthur left the University of Pennsylvania to accept a position at Princeton University. Three years later, he was named Henry Fairfield Osborn Professor of Biology, a chair he held until his death. In 1971 MacArthur discovered that he suffered from a fatal disease and had only a few years to live. He decided to concentrate his efforts on encapsulating his many ideas in a single work. The result, Geographic Ecology: Patterns in the Distribution of Species, was published shortly before his death the following year. Besides a summation of work already done, Geographic Ecology was a prospectus of work still to be carried out in the field. MacArthur died of renal cancer in Princeton, New Jersey, on November 1, 1972, at the age of forty-two.

Achievements

• MacArthur will be remembered as one of the founders of evolutionary ecology. It is his distinction to have brought population and community ecology within the reach of genetics. By reformulating many of the parameters of ecology, biogeography, and genetic into a common framework of fundamental theory, MacArthur, more than any other person who worked during the decisive decade of the 1960’s, set the stage for the unification of population biology.
  
  In addition to his research and teaching activities, MacArthur authored The Biology of Populations with Joseph H. Connell, The Theory of Island Biogeography with Edward O. Wilson, and Geographic Ecology: Patterns in the Distribution of Species.

Works

More photos

• book

  • Geographical ecology; patterns in the distribution of species

    (First published in 1972 and now available for the first t...)

    1972
  • The Theory of Island Biogeography

    (Biogeography was stuck in a "natural history phase" domin...)

    1967

Views

MacArthur proposed that the relative abundance of mutiple related species living in the same community (such as the songbirds of an island) can often be generally approximated by comparison with a stick broken into segments of randomly selected lengths, each segment representing the abundance of a particular species. The rationale was that when species compete, they divide the environment randomly and in a mutually exclusive fashion, like a stick divided into segments.

Membership

• National Academy of Science

• American Academy of Arts and Science

• Ecological Society

Personality

MacArthur was a born naturalist. He watched birds with the patience and skill of a professional ornithologist, visited the tropics as often as he could, and delighted in the endless facts of natural history, which were temporarily exempted from his Cartesian scalpel.

Connections

Robert MacArthur married Elizabeth Bayles Whittemore on June 14, 1952. They had four children - Duncan, Alan, Elizabeth, and Donald.

Father:

John Wood MacArthur

Mother:

Olive (Turner) MacArthur

Spouse:

Elizabeth Bayles Whittemore

Son:

Duncan Macarthur

Daughter:

Elizabeth Macarthur

Son:

Donald Macarthur

Son:

Alan Macarthur

tutor:

G. Evelyn Hutchinson