Profiling the community structure of ectomycorrhizal fungi at endemic pine (Pinus greggii) stands of northeastern Mexico

Abstract

The biological communities of endemic, relictual ecosystems are poorly known and the rate of destruction of these ecosystems is high worldwide. Pinus greggii is a near-threatened Mexican pine endemic species with a highly restricted distribution. In healthy tree stands, the ectomycorrhizal (ECM) symbiosis of trees and fungi is of primary importance; however, the community structure of ECM associated with natural stands of P. greggii has not been studied. Using next-generation sequencing (NGS) (= high-throughput sequencing, HTS), the community of ECM at four natural P. greggii var. greggii stands in the northern Sierra Madre Oriental of Mexico (states of Coahuila and Nuevo Leon) was analysed. A total of 47 516 sequences (runs) and 139 operational taxonomic units (OTUs) of ECM associated with all stands were detected. These ECM communities indicate a community pattern similar to those of boreal forests (albeit with some remarkable absences of taxa), and different from ECM species structures from Neotropical forests. The near absence of Amanitaceae, Boletaceae and Clavulinaceae, and the broad occurrence of gasteroid and corticioid, effuse ECM fungi probably indicates a ECM community adapted to aridity. Many OTUs not assignable to species were detected, which possibly correspond to undescribed taxa. Three genera and 20 species associated with these P. greggii stands are new records for Mexico, including species not previously detected in the Western hemisphere. The most prevalent OTUs across stands belonged to species of Tomentella (25.5%). Taxa in the families Inocybaceae, Rhizopogonaceae, Russulaceae, Sebacinaceae and Tuberaceae were also frequent. NGS-HTS is a powerful and sensitive suite of techniques that yields critical information on ECM communities in forests. This report provides baseline information for future research on biogeography, ecology and applied forestry of pine stands in Mexico, especially P. greggii and associated ECM.

Keywords: symbiosis, soil fertility, high-throughput sequencing, operational taxonomic units