Structure of micrometazoan assemblages in the Larsemann Hills, Antarctica

Abstract

Assemblages of terrestrial biotas in Antarctica have low species-diversity, taxonomic breadth, and number of trophic links and may provide insights not only into adaptation to extreme environments, but also into an understanding of community structure and dynamics not readily achieved by studying more complex, less tractable, systems. To this end, we collected core-samples of soils and the Bryosystem in the Larsemann Hills, Antarctica, and extracted their contained micrometazoans (tardigrades, rotifers, and nematodes). All these undergo deep, sustained dormancy that enhances their survival under extreme polar conditions. Yields varied greatly (zero to > 1000 per core); 38% of the cores lacked animals entirely and only 13% contained all three taxa together. There were greater abundances in mosses, especially at wet seepages, than in lichens or soils. All taxa occurred in mosses more often than expected from random distribution among habitats, and similar "preferences" were shown by tardigrades and rotifers for soil, nematodes for lichens and tardigrades for algae. Whereas tardigrades and rotifers both occur in soil less often than expected by chance, nevertheless are associated with each other there, suggesting that although soil is a relatively unfavorable habitat for both, they respond in similar ways to variation in edaphic conditions. The above scenario serves as a baseline for assessing increasing structural complexity of Antarctic terrestrial communities as the continent undergoes warming, accompanied by inevitable invasion by external species, including non-cryptobiotic taxa.