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Lack of global population genetic differentiation in the arbuscular mycorrhizal fungus Glomus mosseae suggests a recent range expansion which may have coincided with the spread of agriculture

Authors


  • Søren Rosendahl is a professor in mycology whose research focuses on ecology and evolution of mycorrhizal and pathogenic fungi. He has a special interest in population genetics of asexual fungi and the significance of recombination in fungal populations. Peter McGee is an associate professor who has studied the ecology of arbuscular mycorrhizal and others soil fungi in a range of environments in Australia. Joe Morton is a professor and curator whose research focuses on understanding and applying systematic principles to manage an international collection of living glomeromycotan fungi (INVAM), with special interest in evolutionary biology and ecology.

Søren Rosendahl, Fax: +45 3532 2321; E-mail: soerenr@bio.ku.dk

Abstract

The arbuscular mycorrhizal fungus Glomus mosseae is commonly found in agricultural fields. The cosmopolitan species is found in Africa, Europe, America, Asia and Australia. Three hypotheses may explain this worldwide distribution: First, speciation occurred before the continents separated 120 Ma; second, the distribution is a result of human-mediated dispersal related to agriculture and finally, the morphologically defined species may encompass several local endemic species. To test these hypotheses, three genes were sequenced from 82 isolates of G. mosseae originating from six continents and the resulting sequences analysed for geographical subdivision and estimation of migration between continents. Coalescent analyses estimated divergence and age of mutations. Bayesian coalescent modelling was used to reveal important past population changes in the global population. The sequence data showed no geographical structure, with identical genotypes found on different continents. Coalescence analyses indicated a recent diversification in the species, and the data could be explained by a recent population expansion in G. mosseae. The results of this study suggest that speciation and the range expansion happened much later than continental spread and that human activity may have had a major impact on the dispersal and the population structure of the fungus.

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