A.B. Frank and mycorrhizae: the challenge to evolutionary and ecologic theory

Abstract

A. B. Frank’s observations and hypotheses about mycorrhizae in 1885 flew in the face of conventional thinking of the time. He reported that what we now term ectomycorrhizae were widespread on root systems of many woody plant species in a great diversity of habitats and soils. He hypothesized that mycorrhizae represent a pervasive mutualistic symbiosis in which fungus and host nutritionally rely on each other; that the fungus extracts nutrients from both mineral soil and humus and translocates them to the tree host; and that the tree, in turn, nourishes the fungus. Initially opposed by much of the scientific community, nearly all of Frank’s major hypotheses have since been unequivocally demonstrated, although many decades were required to achieve conclusive evidence. Nonetheless, the revolution in thinking about plant and fungal evolution, ecology and physiology generated by Frank is still in the process of acceptance by much of the scientific community, 120 years and tens of thousands of scientific papers since he coined the term “mycorrhiza”. The reasons for this extraordinary lag time in themselves present an intriguing research subject.