Meeting Abstract

P3.107  Tuesday, Jan. 6  The Evolution of the Thaliacea and Its Significance for Tunicate Phylogeny GOVINDARAJAN, A.F.**; BUCKLIN, A.; MADIN, L.P.; Woods Hole Oceanographic Institution, MA; University of Connecticut, Avery Point; Woods Hole Oceanographic Institution, MA afrese@whoi.edu

Thaliaceans are pelagic tunicates that have a close relationship with the benthic and relatively more studied ascidians. The Thaliacea is composed of 3 holoplanktonic groups exhibiting varying degrees of coloniality and life cycle complexity: the Pyrosomatida, Salpida, and Doliolida. Previous studies based on 18S rDNA sequences have shown that the Thaliacea falls within the Ascidiacea. However, the exact relationships within the Thaliacea and between thaliacean and ascidian lineages remain to be detailed. A major limitation to date in reconstructing thaliacean phylogeny has been the availability of samples for sequencing. Thaliaceans are relatively difficult to obtain and preserve, and there are few experts capable of accurate species identification. Here, we present a phylogeny of the Tunicata that includes new 18S rDNA sequences for all 3 thaliacean lineages. We also examine the relationships within the thaliacean lineages and discuss implications for life cycle evolution.