| The biogeography of microbial communities in tropical environment is poorly understood. Recent works in soil microbial ecology have focused on cataloging the diversity of soil bacteria, but few of them have documented how soil bacterial communities are affected by a wide range of biotic (fern species) and abiotic (season and study sites, including soil properties) factors.The objective of this work was to analyze biotic and abiotic factors that could affect the biogeography and composition of microbial communities associated with the rhizosphere of two common ferns, Gleichenella pectinata (GP) and Sticherus bifidus (SB) at a copper deposit in Bosque del Pueblo, Barrio Vegas Arriba in Adjuntas (BPA) and a reference site (Bosque Estatal de Maricao, Barrio Tabonuco in Sabana Grande, BEM) during the dry and the wet seasons. The biogeography of rhizosphere-associated microbial communities was evaluated using Terminal Restriction Fragment Length Polymorphisms (TRFLP) and clone libraries. Abiotic factors such as available phosphorus (P), exchangeable calcium (Ca), magnesium (Mg) and potassium (K), organic matter percentage (OM %), total copper (Cu) content and pH were also studied. Data were analyzed using a combination of statistical tools, such as multivariate analysis. Differences in soil microbial community composition were observed and associated with the presence of Firmicutes, Actinobacteria, Proteobacteria, Fusobacteria, Cyanobacteria, Nitrospira, Fibrobacteres and Bacteroidetes. Microbial communities associated with both ferns appeared to be more influence by season, than by fern specie or study site. At BPA, microbial communities from samples collected appeared to be influenced by Cu, P and K while those from BEM were apparently influenced by Ca, Mg, pH taken in H 2O and in CaCl2. Microbial communities associated with GP site collected at BEM revealed that their biogeographical distribution during the dry season appeared to be more similar than during the wet season. In contrast, those associated with the SB site seems to have a similar biogeographical distribution during both seasons. The biogeography of microbial communities associated with the GP collected at BPA appeared to be different regardless of the seasons. In contrast, surface communities associated with SB during both seasons and the subsurface communities during the wet season appeared to be similar, but communities at different depths during the dry season were not. This study indicates that different tropical forests within the same geographical region can have different microbial communities due to differences in soil properties, seasons, fern species and study sites. |
