Spore diversity of arbuscular mycorrhizal fungi in human-modified neotropical ecosystems

Neotropical landscapes are diverse mosaics of ecosystems commonly resulting from different degrees of human intervention. Although easily recognized by their vegetation, the associated soil microbiota including arbuscular mycorrhizal fungi (AMF) is little known. In Mexico, native tropical rainforest and native savannas are rapidly vanishing, remaining in few spots surrounded by human-made ecosystems. It is unknown, however, how such vegetation types differ in their AMF communities. We compared the spore diversity, spore density and root colonization by AMF in contiguous mosaics of tropical rainforest, savanna and two pine plantations, one managed and the other unmanaged. We detected indicator species associated with tropical rainforest. The savanna displayed the highest values of root colonization of AMF and the lowest spore density. Conversely, the highest spore density and the lowest root colonization rates were found in the tropical rainforest. The two pine plantations showed intermediate values of spore density and colonization between tropical rainforest and the savanna. We did not detect significant seasonal differences (between dry and rainy seasons) in AMF species richness, spore density and root colonization within the vegetation types (except for root colonization in the savanna). Soil cation exchange capacity, phosphorus and nitrogen were negatively associated with AMF spore density and species richness. Our findings suggest that contiguous vegetation types in neotropical landscapes may display significant differences in AMF species composition, spore density and root colonization, and that such differences can be explained in part by soil properties and levels of human intervention.