| Summary: | Antarctic terrestrial life has been described as some of the simplest on Earth. The terrestrial animals that have survived the harsh Antarctic environment are composed mostly of microfauna, such as rotifers, tardigrades and nematodes. Numerous studies have hypothesised about the lack of diversity, but few have examined this using empirical data. Molecular studies have been shown to be useful in determining relationships among populations, delineating species boundaries, dispersal patterns, and biogeographic connectivity. However, such studies of these ecologically-important animals are still limited because original taxonomic work has not been revised broadly across Antarctica. It is apparent that species diagnoses are difficult in many cases due to the minute size and conservative morphology of these animals. Here I compile a species diversity list from the microfaunal groups (Chapter I), and also examine morphological and molecular (using the mitochondrial cytochrome c oxidase I gene) data from 371 nematodes (Chapter III), 438 tardigrades and 526 bdelloid rotifers (Chapter IV). These data suggest that a molecular strategy is vital to discern among cryptic species and to delineate species boundaries for microfaunal groups from Antarctica compared to the sub-Antarctic and global distributions. Sequence comparisons showed local endemic and widespread distributed species, even beyond the Antarctic continent. Those widespread species and the wider range of habitats in which they were found may reflect the ability to withstand environmental stresses. Correlations of soil geochemistry and environmental variables were also established with abundance and distribution data for sites as far as 2000 km from Framnes Mountains (67.78° S- 62.79° E) to Bailey Peninsula (66.28º S-110.54º E) in East Antarctica. These data reveal bdelloid rotifers as the most diverse and widespread group inhabiting a broader range of habitats followed by tardigrades and nematodes. In this study I have uncovered potential new species as well as ...
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