Shifting fungal endophyte communities colonize Bouteloua gracilis: effect of host tissue and geographical distribution

Abstract

Communities of root-associated fungi (RAF) commonly have been studied under the auspices of arbuscular mycorrhizal fungi (AMF) or ectomycorrhizal fungi. However many studies now indicate that other groups of endophytic RAF, including dark septate endophytes (DSE) are more abundant in some plants and environments. The common forage grass, Bouteloua gracilis, was used as a model to examine whether RAF also colonize different organs within the same plant and to compare RAF communities from sites across North America, spanning the latitudinal range of B. gracilis (from Canada to Mexico). We compared the RAF communities of organs within individual plants at one site and within plant roots among six sites. With the possible exception of one group related to genus Paraphaeosphaeria there was little evidence that RAF colonized vertically beyond the crowns. Furthermore, although there was some variation in the constitution of rare members of the RAF communities, several taxonomically related groups dominated the RAF community at all sites. These dominant taxa included members in the Pleosporales (related to the DSE, Paraphaeosphaeria spp.), Agaricales (related to Moniliophthora spp., or Campanella spp.) and Hypocreales (related to Fusarium spp.). AMF were notable by their near absence. Similar phylotypes from the dominant groups clustered around adjacent sites so that similarity of the RAF communities was negatively correlated to site inter-distance and the RAF communities appeared to group by country. These results increase the possibility that at least some of these common and widely distributed core members of the RAF community form important, intimate and long lasting relationships with grasses.

• Bouteloua gracilis
• dark septate endophytes
• endophytic fungi
• grassland fungi
• Grasslands National Park
• Janos
• Konza Prairie
• Llanos de Ojuelos
• Sevilleta
• Wind Cave National Park

Tulio Arrendondo and Patricio Martinez hosted our collection at Ojuelos. Ed Fredrickson, Rodrigo Sierra, Eduardo (Lalo) Ponce, Daniel Aceves and Jesus (Chucho) Pacheco provided hospitality and guided collections at Janos. Ari Jumpponen made suggestions and helped collect B. gracilis plants at Konza. Barbara Muenchau shepherded the permit application process at Wind Cave, and Marie Curtin shared data and information about the park. Robert Sissons guided our collections in Grasslands. Jennifer Thompson worked out the logistics of the transcontinental trip, among other things. Undergraduates Katie Nebel, Rob Welter, Danielle Fuller, Ravin Poudel, Anna Locke, Mitchell Nuhn, Kelsey Vaughn, Haleigh White and Mauricio Galdos helped process the large number of samples and data collected. Two anonymous reviewers improved the manuscripts tremendously. The study was made possible by a NSF grant (DEB0715746) to JH.