Abstract
Arbuscular mycorrhizae are important for growth and survival of tropical trees. We studied the community of arbuscular mycorrhizal fungi in a tropical mountain rain forest and in neighbouring reforestation plots in the area of Reserva Biológica San Francisco (South Ecuador). The arbuscular mycorrhizal fungi were analysed with molecular methods sequencing part of the 18 S rDNA. The sequences were classified as Operational Taxonomic Units (OTUs). We found high fungal species richness with OTUs belonging to Glomerales, Diversisporales and Archaeosporales. Despite intensive sampling, the rarefaction curves are still unsaturated for the pristine forest and the reforestation plots. The communities consisted of few frequent and many rare species. No specific interactions are recognizable. The plant individuals are associated with one to ten arbuscular mycorrhizal fungi and mostly with one to four. The fungal compositions associated with single plant individuals show a great variability and variety within one plant species. Planted and naturally occurring plants show high similarities in their fungal communities. Pristine forest and reforestation plots showed similar richness, similar diversity and a significantly nested structure of plant-AMF community. The results indicate that small-scale fragmentation presently found in this area has not destroyed the natural AMF community, at least yet. Thus, the regeneration potential of natural forest vegetation at the tested sites is not inhibited by a lack of appropriate mycobionts.
Highlights
How to maintain biodiversity increasingly draws attention in connection with ecological devastation and climate change
In the 99% similarity analysis, the highest frequency was found for OTU2 corresponding to Rhizophagus intraradices/vesiculiferus/irregularis occurring with 24% of the investigated plant individuals and representing 9.5% of all glomeromycotan sequences
Richness of arbuscular mycorrhizal fungi (AMF) Operational Taxonomic Units (OTUs) for sites, species and individuals We found a high richness of Glomeromycota in the tropical mountain rainforest, on the reforestation plots and within individual plant species
Summary
How to maintain biodiversity increasingly draws attention in connection with ecological devastation and climate change. One example of a biodiversity hotspot is the tropical mountain rain forest in southern Ecuador [1,2,3]. These forests harbour tens of thousands of species that interact with each other. Network theories were applied to analyse species-rich, mutualistic interactions and emphasized plant-animal assemblages such as pollinator and seed disperser webs [8,9,10,11]. Analyses revealed general features in network architecture of fundamental importance for community formation, biodiversity persistence and stability of ecosystems [8,12]. Except for the orchid-mycorrhizal networks on La Reunion, the mycorrhizal associations showed significantly nested assemblages
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