Meeting Abstract

20.4  Thursday, Jan. 3  Molecular Phylogenetic Evidence Clarifies Hydra�s Closest Relatives NAWROCKI, A.M.; University of Kansas, Lawrence nawrocki@ku.edu

Knowledge of the phylogenetic position of model organisms provides a comparative framework for investigating the evolution of development. Hydra has been a key model organism for the study of developmental pathways; however, further insight into the evolution of important pathways relies on comparison not only with other, distantly related model organisms, but also with Hydra�s own close relatives. As part of an effort to elucidate the relationships of Cnidaria, the Cnidarian Tree of Life project (CnidToL; http://cnidarian.info) has been conducting extensive molecular phylogenetic analyses using both mitochondrial and nuclear sequence data. The dense taxonomic sampling in these analyses is producing a detailed phylogenetic framework for interpreting key questions in cnidarian evolution. It has been proposed that Hydra is a member of Aplanulata (sensu Collins), a putative clade of hydrozoans characterized by the lack of a free-swimming planula larva. Recent molecular phylogenetic analyses support the monophyly of Aplanulata and the inclusion of Hydra into this almost exclusively marine clade. Clarification of Hydra�s position within Aplanulata provides context for future comparative studies in evolution and development utilizing other members of the Aplanulata. The phylogenetic patterns of Aplanulata, including a discussion of life history evolution and the placement of Hydra within this diverse clade, will be presented.