Phylogenetic relatioships of the ascidian Synoicum adareanum: first insights using COI (cytochrome-oxidase

PAULA WIERNES; RICARDO SAHADE; CRISTIAN LAGGER; MARCOS TATIÁN; MARINA CHIAPPERO

Los Cocos, Córdoba

Workshop; First IMCOAST Workshop; 2010

The colonial ascidian Synoicum adareanum (family Polyclinidae) has an exclusively Antartic distribution range and presents two morphotypes, one green with elongated colonies and the other orange and round colonies. In this study, we attempted to explore the relationships among morphotypes and populations of this species using the mitochondrial gene cytochrome oxidase I (COI). We sequenced COI in 56 individuals from five populations with different composition of morphotypes: 25 de Mayo (King George) Island (orange), Livingston Island (unknown), Low Island (Site 1, green and orange), Low Island (Site 2, green and orange) and Melchior (orange). COI sequences from other ascidian species were retrieved from GenBank for comparisons. Fifteen haplotypes were detected, all of them translated to a protein sequence, without premature stop codons. A maximum parsimony tree separated them into two, highly divergent groups. The first group consisted of four haplotypes found in green individuals from Livingston and Low (Sites 1 and 2) and Livingston Island, that joined with ascidian species of the genus Aplidium. The second group consisted in highly divergent haplotypes found in the orange individuals and in a few green individuals from Low Island. We will discuss several hypothesis explaining the high nucleotide divergence observed among this last group.