Determining the Eukaryote Phylogeny

Gayle Philip1, James McInerney2, National University of Ireland, Maynooth;, National University of Ireland, Maynooth

Researchers have often been divided on the relationship of nematodes to arthropods and vertebrates. Traditionally, vertebrates and arthropods have been grouped together with nematodes occupying a basal position. This classic hypothesis, named “Coelomata” argues that vertebrates and arthropods are more closely related as they have a true body cavity (coelem), which nematodes lack. However, a recent hypothesis now joins the nematodes with the arthropods in a molting clade, the Ecdysozoa. Since the publication of the Ecdysozoa hypothesis, evidence has appeared both for and against it. It was our aim to test these hypotheses. Our approach was to identify single gene, orthologous families containing a minimum of four members, from ten eukaryotic taxa. The ten taxa represented three vertebrates, two arthropods, one nematode, two yeasts, one parasite and one plant. Species trees for each gene family were constructed to establish their evolutionary relationships. In-house supertree software was then used to find the supertree that best described the relationship in all the gene family trees. This supertree was then robustly supported with bootstrap values and decay indices. Our results found significant support for the traditional Coelomata hypothesis rather than an Ecdysozoa clade.