Evolutionary studies of ectomycorrhizal fungi: recent advances and future directions

Abstract

The three biggest advances in fungal molecular phylogenetics in the last few years have been (1) the huge expansion in data sets, (2) the development of nonribosomal loci for phylogenetic analysis, and (3) the use of increasingly sophisticated types of analyses. In addition, advances in parallel computing hold great promise for dramatic increases in speed of analysis. These changes have had, or will have, a direct impact on mycorrhizal ecology through the use of sequence-based identification and an indirect impact through the conclusions drawn from such studies. One problem in the field has been the accidental addition of erroneous sequences to the public databases through a variety of means, including polymerase change reaction contamination. We discuss several examples, suggest ways to identify errors, and argue the case for third-party annotations of sequences. Multiple studies have produced compelling evidence that the ectomycorrhizal habit has developed convergently in multiple lineages of fungi and plants. We reexamine the case for loss of the ectomycorrhizal habit in fungi and show that the results are model dependent.Key words: internal transcribed spacer (ITS) region, peroxidase genes, likelihood models, erroneous data, ectomycorrhizal habit.