Environmental conditions shape soil bacterial community structure in a fragmented landscape

Abstract

Several biogeographical hypotheses have been proposed to explain microbial distribution, but there is ongoing debate about the magnitude of the contribution of niche based processes and historical contingencies in determining patterns of microbial structure. In this context, currently fragmented relict forests of olivillo (Aextoxicon punctatum Ruiz et. Pay.), which belonged to a continuous community along the coast of Chile during the Pleistocene, and their surrounding scrublands are ideally suited for testing these hypotheses, since they remain as patches located at the northern tip of the distribution of the relicts. In each study site, edaphic and geographic variables were determined, and the bacterial structures were evaluated at the genetic and metabolic levels through fingerprint approaches along with multivariate analytical methods including redundancy (RDA) and variance partitioning (VPA) analyses. Forests possessed lower pH, and higher contents of moisture and organic matter. In addition, bacterial communities from both habitats differed, whereas the bacterial communities of the forests in different regions were very similar to each other. Our conclusion is that current abiotic soil factors, but not past events due to the historical connection of the forests, account for the variance in the structure of these soil bacterial communities