Microdiversity is associated with low phylogenetic turnover in the glacier-fed stream microbiome

Stilianos Fodelianakis, Massimo Bourquin, Paraskevi Pramateftaki, Tyler J. Kohler, Michail Styllas, Matteo Tolosano, Vincent De Staercke, Martina Schön, Jade Brandani, Hannes Peter and Tom J. Battin, Ecole Polytechnique Federale de Lausanne, Lausanne, Switzerland, Alex Washburne, Montana State University, Alex Washburne, Selva Analytics LLC, Bozeman, MT, Susheel Bhanu Busi and Paul Wilmes, University of Luxemburg, Esch-sur-Alzette, Luxembourg

Background/Question/Methods
Microdiversity, the organization of microorganisms into groups with closely related but ecologically different sub-types, is widespread and represents an important linchpin between microbial ecology and evolution. However, the connection between ecological and phylogenetic patterns of microdiversity has been largely overlooked and it is yet unclear which clades are microdiverse and what is their pattern of abundance across environments in which they are found. The presence of microdiversity increases the niche occupancy of a clade and should thus result in low phylogenetic turnover, suggesting that clades with low phylogenetic turnover are potential hotspots for microdiversity. Here we test this hypothesis in glacier-fed streams (GFS) by developing and applying a novel framework that detects clades with low phylogenetic turnover.
Results/Conclusions
We show that microdiversity is indeed associated to low phylogenetic turnover in the sediment microbiome of (GFS) by identifying several clades that have particularly lower spatial phylogenetic turnover and that contain higher levels of microdiversity than other clades. Overall these clades constituted ~44% and ~64% of community α-diversity and abundance, and both percentages increased further in GFS that were largely devoid of primary producers. Our findings show that in the extreme environment of GFS, a large part of the microbiome is represented by widespread and putatively ecologically successful phylogenetic clades that are also highly microdiverse. This microdiversity could be threatened as glaciers shrink, with unknown consequences for microbial diversity and functionality in these ecosystems.