Asymmetric symbiont adaptation to Arctic conditions could explain why high Arctic plants are non-mycorrhizal

Mycorrhizal symbiosis generally improves nutrient and water acquisition of the host plant. Furthermore, mycorrhizal fungi affect plant herbivory and pathogen resistance. The symbiotic condition of land plants is evolutionarily ancient and the functions performed by the fungal symbiont are thought to be pivotal to successful plant life. Although most land plants are mycorrhizal, the extreme high Arctic habitats are dominated by plant species and genera characteristically free of mycorrhiza. In this paper, previous attempts to explain the lack of mycorrhizas in high Arctic are reviewed as well as a new idea of asymmetric symbiont adaptation is proposed as potential explanation why high Arctic plants are non-mycorrhizal. (c) 2004 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved.