HAPLOTYPE DIVERSITY AND GENETIC DIFFERENTIATION AMONG FOUR POPULATION OF THE COLONIAL ASCIDIAN SYNOICUM ADAREANUM

PAULA WIERNES; SAHADE RICARDO; CRISTIAN LAGGER; MILAGROS DEMARCHI; SOLEDAD ACOSTA; MARCOS TATIÁN; LUCIANA TORRE; NATALIA SERVETTO; MARINA CHIAPPERO

Buenos Aires

Congreso; Scientific Committee on Antarctic Research (SCAR) Meeti; 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. The aim of this study was to analyze the levels of genetic variability and differentiation in the mitochondrial gene cytochrome oxidase I (COI) in four 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). Analyses were performed with the programs DnaSP and Arlequin. Nucleotide diversity levels were high in all populations (Pi from 0.009 to 0.284); haplotype diversity was also high (Hd from 0.750 to 0.833). Pairwise genetic differentiation was statistically significant for all comparison, except for that between the two sites of Low Island (Fst from 0 to 0.582). Three out of the 13 haplotypes found were shared among the two sites of Low Island, pertaining to the “green” morphotype; the remaining haplotypes were population-exclusive. A Minimum spanning network showed that the “orange” haplotypes formed two groups, one including all haplotypes of 25 de Mayo Island and one haplotype of Livingston Island, and the other one haplotype of Low Island (Site 1). The “green” haplotypes formed four distinct groups, showing a large genetic differentiation among them. Our results indicate that variability in morphology and coloration are linked to the degree of genetic differentiation, although we also observed a high differentiation among individuals of the same morphotype and the same population.