Globally Distributed Arbuscular Mycorrhizal Fungi Associated With Invasive Cinchona pubescens on Santa Cruz Island, Galápagos

The presence of arbuscular mycorrhizal fungi (AMF) is essential for the survival and establishment of most plant species in nature. The reproductive success of invasive plant species in a particular habitat could also depend on these AM fungi. Cinchona pubescens, commonly known as quinine, is highly invasive on Santa Cruz Island, Galápagos, but at the same time severely endangered in its native range on mainland Ecuador due to overexploitation in the past. In this study, we aim at determining the AMF communities associated with C. pubescens at both locations to investigate whether the successful invasion of C. pubescens on Santa Cruz is related to its association with a particular community of AMF. For this, roots of C. pubescens trees were sampled at three sites, one site on Santa Cruz and two sites in the province of Loja, on mainland Ecuador. Communities of AM fungi were determined through the molecular cloning and sequencing of the 18S nrDNA gene and through the delimitation of Operational Taxonomic Units (OTUs), associated with the plant roots. We found 36 AMF OTUs associated with C. pubescens, most of them belonging to the genus Glomus. The highest richness of AMF OTUs was detected in samples from sites located on mainland Ecuador. The AMF communities between Santa Cruz and mainland Ecuador were significantly different, and only five OTUs were shared between both locations. Two dominant OTUs in C. pubescens from Santa Cruz were detected but no dominant OTUs from mainland Ecuador. Almost two thirds of the OTUs associated with C. pubescens had a wide global distribution. Our results suggest that the successful invasion of C. pubescens on Santa Cruz could have been facilitated by local generalist AMF and not by particular AMF. The observed generalist AMF from both locations could be important for conservation plans of restoring the endangered C. pubescens in the native forests on mainland Ecuador.