Foraminifera and Cercozoa are related in actin phylogeny: Two orphans finda home?

In recent years, the increased sampling of protein-coding genes from divers e eukaryotes has revealed that many aspects of each gene tree are at odds w ith other phylo genies. This has led to the belief that each gene tree has unique strengths and weaknesses, suggesting that an accurate picture of euk aryotic relationships will be achieved only through comparative phylogeny u sing several different genes. To this end, actin genes were characterized f rom two genera of chlorarachniophytes, Chlorarachnion and Lotharella, and t hree species of the cercomonad flagellate Cercomonas. Phylogenetic trees in cluding these new actin genes confirm the recently proposed relationship be tween chlorarachniophytes and cercomonads (Cercozoa) and, more importantly, also show a close relationship between Cercozoa and Foraminifera. Both of these are major eukaryotic groups encompassing extremely diverse organisms, yet there is no strong evidence for the evolutionary position of either fr om morphological or molecular data. The union of Cercozoa and Foraminifera suggested by actin phylogeny represents a novel step in the long process of determining the broad relationships between all major eukaryotic groups.