ABSTRACT
Geothermal springs are model ecosystems to investigate microbial biogeography as they represent discrete, relatively homogenous habitats, are distributed across multiple geographical scales, span broad geochemical gradients, and have reduced metazoan interactions. Here, we report the largest known consolidated study of geothermal ecosystems to determine factors that influence biogeographical patterns. We measured bacterial and archaeal community composition, 46 physicochemical parameters, and metadata from 925 geothermal springs across New Zealand (13.9-100.6 °C and pH < 1-9.7). We determined that diversity is primarily influenced by pH at temperatures <70 °C; with temperature only having a significant effect for values >70 °C. Further, community dissimilarity increases with geographic distance, with niche selection driving assembly at a localised scale. Surprisingly, two genera (Venenivibrio and Acidithiobacillus) dominated in both average relative abundance (11.2% and 11.1%, respectively) and prevalence (74.2% and 62.9%, respectively). These findings provide an unprecedented insight into ecological behaviour in geothermal springs, and a foundation to improve the characterisation of microbial biogeographical processes.