One Core to Root them All: A Core Bacterial Community in Closely Related but Geographically Distant Mammillaria Species from Contrasting Environments

Abstract

Abstract Understanding the core microbiome has potential applications on biomonitoring and conservation. We explore whether closely related xerophytes from the M ammillaria h aageana s pecies c omplex (MHSC), a recently diverged group (ca. 2 mya) that occupy geographically distant and contrasting environments, share a bacterial core microbiome (BCM) that could help them to thrive through an aridity gradient. We sampled the rhizosheath and the surrounding bulk soil, performed 16S rRNA (v3-v4 region) metabarcoding, and analyzed soil properties, bacterial diversity and functional predictions, to compare between soil compartments and describe the BCM associated to the MHSC rhizosheath. We observed that bacterial communities differed among bulk soils but MHSC species display a trend to select for the same bacteria. Despite environmental differences, we found that all four species shared a BCM composed of 17 bacterial taxa, assigned to genera Dactylosporangium , Microvirga , and Rubrobacter ; as well as 14 predicted functional processes. This BCM could enhance rhizosheath nutrient acquisition and stress responses, thus helping the plant-bacteria holobiont to thrive in arid environments and help us understand the rapid evolution and diversification of the MHSC across an aridity gradient