Legacy of former glacial hisotry is imprinted on the spatial distribution of bacterial communities in the maritime Antarctic

Abstract

Biological evidence of former glacial fluctuations in Antarctica has been sought mainly on cryptogam and invertebrate communities, while soil microbial assemblages were almost neglected or examined at short timescales without enough spatial coverage. Here, we examined the spatial distribution of soil bacterial communities and their relation to local environmental gradients in ice-free region of the maritime Antarctic. Spatial mapping of bacterial communities revealed that soil pH was the primary driver of bacterial community structure but a large proportion of remaining community composition was spatially structured following the post-Last Glacial Maximum (LGM) deglaciation trajectory which was evidenced by glacial striations and geochemical signatures remained on outcrops. The successional trend was also supported by the shifts in bacterial community traits (e.g. decrease in rRNA operon copy number and phyla abundance changes over the course of succession) which are commonly observed along the chronosequence of deglaciated terrain. Variation partitioning revealed that a large proportion of local environmental gradients are spatially structured at broad scales (<10km) and there is no fine-scale spatial structure, suggesting the negligible role of dispersal process at local scale. In addition, considerable proportion of community variation were explained by geochemical properties, indicating that geochemistry as well as edaphic components play equally important roles in structuring bacterial communities in this extreme environment. These results provide the first evidence that the legacy of former glacial history since the LGM remained on the contemporary spatial distribution of soil bacterial communities in the maritime Antarctic.