XVI International Botanical Congess
In rRNA phylogenies, amitochondriate protists are basal to all other eukaryotes and the evolution of at least four complex assemblages was nearly concurrent with plants, animals and fungi. More than any other gene, rRNAs link organisms of similar phenotypes. Yet, other molecules suggest alternate relationships including a link between microsporidia and fungi. These reassignments and detection of genes not expected in basal amitochondriate lineages challenge simple interpretations of the rRNA trees. For example, discoveries of mitochondrial heat shock genes in Giardia, Trichomonas and microsporidia imply mitochondria were present in the first eukaryotes. Explanations for these conflicting results await new models and acquisition of genome sequences from diverse protists. Initial genome data from Giardia already suggests that lateral gene transfer between eukaryotes might be relatively common.