Structure and diversity of ectomycorrhizal resistant propagules in Pinus montezumae neotropical forests and implications for seedling establishment

Abstract

Ectomycorrhizal (ECM) fungal communities have been relatively poorly documented in neotropical forests. We analyzed the structure and diversity of the ECM resistant propagules present in the soil of Mexican neotropical forests dominated by Pinus montezumae. Soil samples were collected under mature P. montezumae, and microcosms were set up with bioassayed seedlings. The ECM propagules were formed by relatively few taxa that were evenly distributed across the sampled area. Some taxa, such as Rhizopogon spp. and Atheliaceae sp., formed an extensive mycelial system, which is likely to confer them with an advantage for seedling colonization. We also compared the species composition of the ECM propagules with the ECM communities previously assessed on the roots of seedlings and adult trees. They were represented by different taxa, although similarity analyses did not detect differences in species occurrence. Only two taxa, belonging to the Atheliaceae family, were shared between field and bioassayed seedlings, whereas 12 taxa were common to field seedlings and adult trees. The lower similarity between bioassayed and field seedlings suggests that fungal taxa found as resistant propagules are not active in mycelial networks in field conditions and that mycorrhizal network-mediated colonization may be prevalent in this neotropical forest.