their plant hosts. While it is generally accepted that interactions between organisms will affect their response to global climate change, we still lack the ability to predict the outcome of these interactions in future climates. In recent meta-analyses, AM fungi were found to increase plant biomass under drought conditions and decrease plant biomass under simulated nitrogen deposition studies. Arbuscular mycorrhizal fungi themselves have been shown to increase their biomass in response to elevated atmospheric Plants lacking arbuscular mycorrhizae Members of the mustard family (Brassicaceae), such as cabbage, cauliflower, canola, and crambe, do not establish arbuscular mycorrhizal fungi on their roots. Molecular genetic analyses of arbuscular mycorrhizal fungi In the past ten years there have been spectacular advances in molecular genetic technologies and tools. These advances allow microbial and mycorrhizal ecologists to ask new and exciting questions about the ecological and evolutionary roles of arbuscular mycorrhizal (AM) fungi as individuals, in communities and ecosystems. Genetic analyses of AM fungi have been used to explore the genetic structure of single spores using multilocus genotyping, AM fungal diversity and adaptation across multiple grassland communities, all the way up to a global investigation of AM fungal diversity, which greatly increased the described molecular diversity within the phylum Glomeromycota. All the recent advances in molecular genetics clearly permit the analysis of microbial communities at much finer and functional scales and potentially with more confidence than previous methods. The classical AM fungal identification method of spore extraction from soil and further spore morphological analysis is fraught with complicating issues due to the various strategies and forms of AM fungi, e.g., lack of sporulation in certain species, seasonality, high unculturability, possible misidentification (human error), and new evidence of multi-nucleate spores and high genetic variation within clonal AM species. Because of these various problems, in the past researchers likely misrepresented the true composition of AM fungal communities present at any one point in time or place. Additionally, by following the traditional extraction, culture and microscopic identification methods, there is no way to determine active/functioning AM fungal populations, which are likely the most important when attempting to relate plant-AM symbiotic interactions and mechanisms to ecological or ecosystem function. This is especially true in the case of root colonization analyses, which can determine percentage of roots colonized by AM fungi. The major problem with this analysis is in field soils, which contain multiple species of AM fungi in association with