. Annual report. Harvard University. Museum of Comparative Zoology. A clear picture of evolutionary relationships among species is needed to reconstruct how they diversified physically and ecologically over time. In the animal tree of life, placement of the flatworm group Acoelomorpha has great importance for understanding critical events in animal evolution, in particular the origin and evolution of numerous organ systems. Yet, positioning this group has been problematic for taxonomists due to their rapid evolution and a lack of genomic data for certain acoelomorph groups. In a study publishe
. Annual report. Harvard University. Museum of Comparative Zoology. A clear picture of evolutionary relationships among species is needed to reconstruct how they diversified physically and ecologically over time. In the animal tree of life, placement of the flatworm group Acoelomorpha has great importance for understanding critical events in animal evolution, in particular the origin and evolution of numerous organ systems. Yet, positioning this group has been problematic for taxonomists due to their rapid evolution and a lack of genomic data for certain acoelomorph groups. In a study published in Proceedings of the Royal Society of London, Gonzalo Giribet and an international team of scientists place Acoelomorpha at the first evolutionary branching for bilateral animals. The researchers determined that this group of simple worms is a product of the deepest evolutionary split within bilateral creatures— multicellular organisms that, like humans, have bilaterally symmetrical body forms. The team employed a genetic sequencing technique called expressed sequence tags, which utilized many genes from a large number of species. To obtain and analyze this massive amount of data, the team designed new automated methods for identifying and selecting common genes across different species and developed highly effective supercomputing tools to reconstruct relationships from DNA sequences. The study, funded by the National Science Foundation's Protosome Assembling the Tree of Life Project, represents the most computationally intensive genetic sequencing analysis to date: million supercomputer processor hours were required to obtain the results. Hejnol A, Obst M, Stamatakis A, Ott M, Rouse GW, Edgecombe GD, Martinez P, BaguriaJ, Bailly X, Jondelius U, Wiens M, Muller WEG, Seaver E, Wheeler WC, Martindale MQ, Giribet G, Dunn, CW (2009) Assessing the root of bilaterian animals with scalable phylogenomic methods. Proceedings of tlie Royal Society B 276:4261-4270. Genetic Sex
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