Community structure of ectomycorrhizal fungi in a Pinus muricata forest: minimal overlap between the mature forest and resistant propagule communities

We have investigated colonization strategies by comparing the abundance and frequency of ectomycorrhizal fungal species on roots in a mature Pinus mur icata forest with those present as resistant propagules colonizing potted s eedlings grown in the same soil samples. Thirty-seven fungal species were d istinguished by internal transcribed spacer (ITS) restriction fragment leng th polymorphisms (RFLPs); most were identified to species level by sporocar p RFLP matches or to genus/family level by using sequence databases for the mitochondrial and nuclear large-subunit rRNA genes. The below-ground funga l community found in the mature forest contrasted markedly with the resista nt propagule community, as only four species were found in both communities . The dominant species in the mature forest were members of the Russulaceae , Thelephorales and Amanitaceae. In contrast, the resistant propagule commu nity was dominated by Rhizopogon species and by species of the Ascomycota. Only one species, Tomentella sublilacina (Thelephorales), was common in bot h communities. The spatial distribution of mycorrhizae on mature roots and propagules in the soil differed among the dominant species, For example, T. sublilacina mycorrhizae exhibited a unique bias toward the organic horizon s, Russula brevipes mycorrhizae were denser and more clumped than those of other species and Cenococcum propagules were localized, whereas R. subcaeru lescens propagules were evenly distributed. We suggest that species differe nces in resource preferences and colonization strategies, such as those doc umented here, contribute to the maintenance of species richness in the ecto mycorrhizal community.