Rapid Evolutionary Changes in a Globally Invading Fungal Pathogen (Dutch Elm Disease)

Authors: Brasier C.M.¹; Buck K.W.²

Source: Biological Invasions, Volume 3, Number 3, 2001 , pp. 223-233(11)

Publisher: Springer

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Abstract:

Two enormously destructive pandemics of Dutch elm disease occurred in the 20th century, resulting in the death of a majority of mature elms across much of the northern hemisphere. The first pandemic, caused by Ophiostoma ulmi, occurred as this pathogen spread across Europe, North America and Southwest and Central Asia during the 1920s–1940s. The current pandemic is caused by another Ophiostoma species, O. novo-ulmi. Since the 1940s, O. novo-ulmi has been spreading into the regions previously affected by O. ulmi. It has also spread as two distinct subspecies, termed subsp. americana and subsp. novo-ulmi. This sequence of events has resulted in competitive interactions between these previously geographically isolated pathogens. This article summarizes the biological properties of the Dutch elm disease pathogens and their history of spread. It reviews the remarkable series of genetic events that have occurred during their migrations; including the emergence of genetic clones, the spread of deleterious fungal viruses within the pathogen clones, and the rapid and continuing evolution of O. novo-ulmi via horizontal gene flow. The wider role of horizontal gene flow in the evolutionary potential of migratory plant pathogens is discussed.

Keywords: Dutch elm disease; elms; episodic selection; fungal viruses; horizontal gene flow

Language: English

Document Type: Regular paper

Affiliations: 1: Forest Research Agency, Alice Holt Lodge, Farnham, Surrey GU10 4LH, UK; Author for correspondence (e-mail: clive.brasier@forestry.gsi.gov.uk; fax: +44-1420-23653) 2: Department of Biology, Imperial College, London SW7 2AZ, UK

Publication date: 2001-01-01