Nematodes are known to play important roles in ecosystem functioning, however their specific roles may vary across different taxonomic levels. Correct identification of nematode species is necessary when analyzing their diversity in order to effectively assign their functional role(s). Several different nematode genera are known to inhabit the dry valleys of the McMurdo LTER, but the ecological roles of each of these taxa is still a mystery. One genus of particular interest is Plectus. The taxonomic diversity of these Antarctic inhabitants is currently in flux. To resolve this we have collected both terrestrial and aquatic samples belonging to the Plectus genus and identified them using morphological characters. Using PCR and sequencing of the 28s, 18s, and ITS ribosomal RNA genes we explore patterns of lineage divergence of Plectus in the MCM.