Comparison of ectomycorrhizas of Quercus garryana (Fagaceae) on serpentine and non‐serpentine soils in southwestern Oregon

Abstract

The diversity of ectomycorrhizal communities associated with Quercus garryana on and off serpentine soils was compared and related to landscape-level diversity. Serpentine soils are high in magnesium, iron, and heavy metals and low in fertility. In plant communities on serpentine soils, a high proportion of flowering plant species are endemic. At three sites with paired serpentine and nonserpentine soils in southwestern Oregon, we sampled Q. garryana roots and categorized ectomycorrhizas by morphotyping and by restriction fragment length patterns. Ectomycorrhizas were abundant at all sites; no single fungal species dominated in the ectomycorrhizas. Of 74 fungal species characterized by morphotype and pattern of restriction fragment length polymorphisms, 46 occurred on serpentine soils, and 32 were unique to serpentine soil. These species are potentially endemic to serpentine soil. Similarities in species composition between paired serpentine and nonserpentine soils were not significantly lower than among three serpentine sites or among three nonserpentine sites. We conclude that mycorrhizal communities associated with oaks on serpentine soil do not differ in species richness or species evenness from those on neighboring nonserpentine soil.

Ectomycorrhizal communities of Quercus garryana are similar on serpentine and nonserpentine soils

“…These results were unexpected because fungi take up heavy metals and because some fungi have ecotypes or strains with tolerance to heavy metals (Gadd and deRome 1988;Gadd 1993;Galli et al 1994;Jentschke and Godbold 2000;Meharg and Cairney 2000;Panaccione et al 2001;Colpaert et al 2000). Possible explanations for the finding of similar ectomycorrhizal communities on serpentine and nonserpentine soils by Moser et al (2005) include too great a distance between sites, the weakly serpentinic composition of two of the sites, and lack of molecular confirmation of morphotype identity. Ectomycorrhizas on paired serpentine and nonserpentine sites (1 km apart) were more similar to each other than to those on distantly separated serpentine sites (up to 50 km apart).…”

“…The most abundant and most frequent species of ectomycorrhizas associated with oaks on serpentine soils were the very common fungal species associated with oaks on all soils world wide: C. geophilum, an asexual Ascomycota with sclerotia; hypogeous Ascomycota (Tuber, Genea, Gilkeya, and other Pezizales); crust-forming resupinate Basidiomycota (Sebacina Avis et al 2003;Valentine et al 2004;Moser et al 2005;Richard et al 2005;Walker et al 2005;Frank et al 2006b). Serpentine soils supported extensive mycorrhizal communities.…”

“…All mycorrhizas were sorted by morphotype, a suite of characters including color, branching pattern, emanating hyphae, and mantle peels (Agerer 1991;Valentine et al 2004;Moser et al 2005). To quantify mycorrhiza abundance, we counted individual mycorrhizal root tips.…”

“…Ectomycorrhizas on paired serpentine and nonserpentine sites (1 km apart) were more similar to each other than to those on distantly separated serpentine sites (up to 50 km apart). Only one serpentine site had levels of heavy metals greater than 1000 µg/g and a magnesium-to-calcium ratio greater than two (Moser et al 2005). …”

“…However, Alexander et al (2007) recognized the need to include a mycorrhizal component in studies of the adaptation of plants to serpentine soils. Moser et al (2005) compared the diversity of ectomycorrhizas associated with Q. garryana at three sites with paired serpentine and nonserpentine soils. Ectomycorrhizas were abundant at all sites; communities on serpentine soils were similar in morphotype richness to those on neighboring nonserpentine soils with no single fungal morphotype dominating on either soil type.…”