Discovering the evolution of pancrustaceans within arthropods: prospects and pitfalls of molecular methods including phylogenomic data

Bjoern Marcus von ReumontZoologisches Forschungsmuseum Alexander Koenig, Germany

The reconstruction of the evolutionary history of crustaceans and arthropods is still difficult addressing internal relationships, but also revealing the likely crustacean sistergroup to Hexapoda. Recent molecular studies corroborate Myriapoda as sistergroup to Pancrustacea with paraphyletic crustaceans supporting Remipedia or Remipedia + Cephalocarida as sistergroup to Hexapoda. However, the position of Remipedia and several other groups like Malacostraca within crustaceans still remains ambiguous based on different data sources. A likely scenario of euarthropod evolution based on EST data is, that Remipedia represent the possible link to Hexapoda conquering land habitats.

In the presented phylogenomic approach first 454 EST data of Remipedia were included. Genes were selected from the unreduced dataset applying the matrix reduction software MARE. All reconstructed topologies highly support Remipedia as sistergroup to Hexapoda. The results further support recent studies concluding that critical data evaluation is crucial and new methods are essential for prospective phylogenetic analyses.

To estimate the reliability of the tree reconstructions from phylogenomic data is a major challenge and the handling of long branch taxa is still problematic. This and further issues, e.g. the gene selection and the identification of informative genes are essential to improve our understanding of molecular evolution and phylogenomic data. However, to enlight pancrustacean evolution, it is still crucial to collect more crustacean key taxa (e.g. Cephalocarida). The presented analysis includes first 454 data of Remipedia, Ostracoda, Mystacocarida and Leptostraca. Until now, an overhead of decapod EST sequences is published, while data for non-decapods are very sparse.