Uncovering The Unexplored: The Microbial Ecology Of Sub-AntarcticIsland Soils

Abstract

The sub-Antarctic islands (SAIs) are broadly categorised as those islands positioned around the Antarctic Polar Front and with a biogeographic link to continental Antarctica. Due to their remote locations and wide spatial separations, most have been poorly characterized in terms of macro- and microecology. The remoteness of these islands, and the likelihood that dispersal processes may be limited by the extreme inter-island and island-continent distances, suggests that strong local homogenizing forces may lead to unique microbial community compositions. In 2016-2017, the Antarctic Circumnavigation Expedition (ACE) provided a near-unique opportunity to source biological materials, including soil samples, from a number of these highly inaccessible and rarely visited SAIs. In turn, this provided an unprecedented opportunity to investigate, and compare the soil microbial ecology of these locations. In the present study, we describe the unique microbial biodiversity of SAI soils, with a specific focus on the role of local habitat selection in shaping community structure and functional potential. Taxonomic comparison of the soil communities indicated that the various SAIs harboured spatially segregated microbiomes with a limited degree of overlap. However, we identified a shared microbial fingerprint of lichen-associated taxa, suggesting that terrestrial lichens may be key drivers of sub-Antarctic island soil microbial ecology. In addition, investigation of the functional profiles of these soil microbial communities suggested a location-specific specialization shaped primarily by the temperature range of the SAI habitats. The results presented in this study represent the most extensive characterization of the microbial ecology of the SAI soils to date.