Cruzamientos Interpoblacionales En Mitylus Chilensis

Genetics and Molecular Biology, 29, 1, 174-179 (2006) Copyright by the Brazilian Society of Genetics. Printed in Brazil www.sbg.org.br Short Communication

Allozymic variation and differentiation in the chilean blue mussel, Mytilus chilensis, along its natural distribution
Jorge E. Toro, Grace C. Castro, Johana A. Ojeda and Ana M. Vergara Universidad Austral de Chile, Instituto de BiologíaMarina “Dr. Jürgen Winter”, Valdivia, Chile. Abstract
Genetic differentiation in the Chilean blue mussel Mytilus chilensis (Hupé 1854) was investigated based on the variation in the allozyme frequencies of Pgm, Gpi, Icd, Me, Gsr, Lap and Pep in eight samples collected along 1800 km from Arauco (VIII Region) to Punta Arenas (XII Region). Despite the large geographic separations, values of Neisunbiased genetic distance, D (0.004-0.048) and standardised genetic variation among populations, Fst (0.011-0.055) were small. The levels of gene flow (Nm = 8) found in this study prevent the effect of differentiation among populations by genetic drift. This findings indicate that its long-lived planktotrophic larvae provides this species with considerable dispersal ability throughout its range which isfavoured by the ocean currents along the chilean coast. In terms of management of the M. chilensis fishery, the results provide no evidence for discrete stocks, with the possible exception of the Punta Arenas population. Considering the intensive aquaculture activities with this species the present study provide preliminary data which can be used as a baseline for further characterization and /ormonitoring these mussel populations. Key words: allozyme, Mytilus chilensis, population genetics, gene flow, Chile. Received: July 21, 2004; Accepted: May 31, 2005.

The Chilean blue mussel (Mytilus chilensis, Hupe 1854) is an economically important resource in southern Chile, commonly known as chorito or quilmahue. It is widely distributed on hard substrata in the lower intertidal zone to 25 mdepths, along the chilean coast line (Brattström and Johanssen, 1983). The range of the species extends over 40° of latitude from Arica to Cape Horn (Lancellotti and Vázquez, 2000) and it is impacted by a major oceanographic feature, the West Wind Drift (43°S) that defines the boundary between the main current directions along the chilean Coast (Strub and Mesías, 1998). Winter et al. (1984),determined that there was an annual reproductive cycle, with spawning occurring during spring and summer. Toro and Sastre (1995) and Toro et al. (2004) have shown that M. chilensis possesses a planktotrophic larval stage with a pelagic existence of 45 d. The species thus has the potential for long-distance dispersal over a scale of hundreds of kilometers along the chilean coast. Its culture began in1943 in the Chiloé Island, southern Chile (Osorio et al., 1979) and the aquaculture production raised from 3,864 t in 1993 to 41,406 t in 2001. Despite this explosive development of M. chilensis aquaculture, population genetics studies in the chilean mussel (Mytilus chilensis) are scarce
Send correspondence to Jorge E. Toro. Universidad Austral de Chile, Instituto de Biología Marina“Dr. JürgenWinter”, Casilla 567, Valdivia, Chile. E-mail: jtoro@uach.cl.

in the literature. Only a few studies with limited sampling are reported in the scientific literature mainly focused to dilucidate the distribution of the Mytilus edulis species complex (Koehn, 1991; McDonald et al., 1991). An important question, from both evolutionary and fishery amangement perspectives, is the extent of gene flow andassociated genetic differentiation among Mytilus chilensis populations at a macrogeographic (over 100 km) scale. Marine species with longer larval phases are generally though to disperse further and have more gene flow, larger geographic ranges, lower levels of genetic differentiation among populations, and high levels of genetic variation within populations (Scheltema and Williams, 1983;...