Endorhizal Fungi in Ranunculus from Western and Arctic Canada: Predominance of Fine Endophytes at High Latitudes

Ranunculus roots were sampled across a latitudinal transect encompassing 52 oN and 82 oN, for years spanning 1963-2007. Samples from 2004 and later were preserved in formalin; earlier samples were taken from herbarium accessions. Roots were examined for colonization by arbuscular mycorrhizae, fine endophyte, and septate endophyte fungi using lactofuchsin-stained material imaged with epifluorescence microscopy. Endorhizal quantitation was assessed for each endorhizal morphotype. Roots from High Arctic (79 oN-82 oN) and mid-latitude (52 oN-54 oN) sites both contained all three endorhizal morphotypes; however, overall fungal colonization was almost three-fold higher in midlatitude samples. Most Ranunculus root colonization (29 % of the root length) in High Arctic samples was from fine endophyte fungi, whereas fine endophyte colonization was ~ 20 % of root length in mid-latitude roots. In contrast, arbuscular mycorrhizal colonization was 2 % of root length in High Arctic samples and 57 % in mid-latitude samples. Septate endophyte colonization was 11 % and 36 % of root length for High Arctic and mid-latitude samples, respectively. These values are consistent with our previous results for other taxa, and suggest that fine endophytes are important contributors to soil microbial diversity as related to plant survival and competitiveness in the high latitudes.