Fungi recognised as a separate kingdom

In 1969 Robert H. Whittaker published the paper "New Concepts of Kingdoms of Organisms" in Science. He proposed five kingdoms: Monera, Protista, Plantae, Fungi and Animalia. Fungi were given a separate place in it, because their manner of organisation and nutrition did not fit the plants to which they had traditionally been attached.

Whittaker drew attention not only to appearance but also to ecological roles. Plants above all produce organic matter through photosynthesis, animals take in food and digest it inside the body, and fungi secrete enzymes into the substrate and absorb the products of decomposition. A hyphal construction increases the area of contact with that substrate. These differences justified a kingdom Fungi even before molecular data came into general use.

The five-kingdom system is not the last word on the classification of life. Later, studies of ribosomal RNA led to the concept of three domains, and phylogenomics revealed many deep lineages of eukaryotes that the old Protista could not accommodate. At the same time, sequences confirmed an important intuition: fungi are not plants, and belong with animals to the Opisthokonta.

The significance of the 1969 paper was educational and conceptual. It changed the way textbooks presented fungi, and it connected classification with an organism's function in an ecosystem. Reading the original, one sees science as a developing model: Whittaker's system can be improved today without taking away its role in the shift from external resemblance to an evolutionary and ecological understanding of kingdoms.

A separate kingdom appears before 1969

The event date needs interpretive correction. In his 1959 paper Whittaker had already proposed four kingdoms: Protista, Plantae, Fungi, and Animalia. He justified separating fungi through three evolutionary directions of nutrition: photosynthesis in plants, ingestion in animals, and absorption in bacteria and fungi. He also distinguished their ecological role as reducers from producers and consumers. The Science paper published on 10 January 1969—volume 163, pages 150–160—presented the later five-kingdom arrangement, in which Monera received separate kingdom rank. Thus 1969 is a sound marker for the familiar five-kingdom model, but it is not the first date on which Whittaker proposed Fungi as a kingdom.