Studies of microbial biogeography are often convoluted by extremely high diversity and differences in microenvironmental factors such as pH and nutrient availability. Desert endolithic (inside rock) communities are relatively simple ecosystems that can serve as a tractable model for investigating long-range biogeographic effects on microbial communities. We conducted a comprehensive survey of endolithic sandstones using high-throughput marker gene sequencing to characterize global patterns of diversity in endolithic microbial communities. We also tested a range of abiotic variables in order to investigate the factors that drive community assembly at various trophic levels. Macroclimate was found to be the primary driver of endolithic community composition, with the most striking difference witnessed between hot and polar deserts. This difference was largely attributable to the specialization of prokaryotic and eukaryotic primary producers to different climate conditions. On a regional scale, microclimate and properties of the rock substrate were found to influence community assembly, although to a lesser degree than global hot versus polar conditions. We found new evidence that the factors driving endolithic community assembly differ between trophic levels. While phototrophic taxa, mostly oxygenic photosynthesizers, were rigorously selected for among different sites, heterotrophic taxa were more cosmopolitan, suggesting that stochasticity plays a larger role in heterotroph assembly. This study is the first to uncover the global drivers of desert endolithic diversity using high-throughput sequencing. We demonstrate that phototrophs and heterotrophs in the endolithic community assemble under different stochastic and deterministic influences, emphasizing the need for studies of microorganisms in context of their functional niche in the community.
Bibliographical noteFunding Information:
We thank the entire staff of Timna Park for their kind hospitality during our field expedition. We also thank the staff of the Gobabeb Research and Training Centre (Namibia) for their support in the field, the Cape Bounty Arctic Watershed Observatory and Environment Canada’s Eureka Weather Station for logistical support, and Kevin Hsiao and Emine Ertekin for field support in Utah. We also acknowledge the technical support of Michael McCaffery for microscopy analysis. Funding. This work was supported by NSF grant DEB1556574 and NASA grant NNX15AP18G.
© Copyright © 2020 Qu, Omelon, Oren, Meslier, Cowan, Maggs-Kölling and DiRuggiero.
- microbial assembly
- trophic level