Abstract

Natural populations of Ostrea chilensis have suffered strong declines during the last two decades due to overfishing that forced in some locations to carry out restocking and culture with juvenile oysters from other local populations. It has been proposed that this type of intervention may have affected the levels of genetic variation among natural populations. Here we analyzed the genetic variation in two natural populations and in three populations affected by restocking of O. chilensis, sampled along its whole natural distribution, by means of Random Amplified Polymorphic DNA (RAPD) analyses. The values of Nei's genetic distance did not reveal significant differences among populations (0.0713 and 0.1549). The Mantel test using 5000 randomizations, showed a significant correlation between genetic and geographic distance. Melinka, the most geographically distant population, was the most genetically differentiated. The levels of gene flow (Nm = 1.587) are strong enough to prevent differentiation due to genetic drift. With these results, the genetic-population structure of O. chilensis, can be characterized a panmictic population, in which, the level of gene flow prevents significant genetic differentiations among populations. However, the population-genetic structure of this species does not depend exclusively on its breeding strategy, since other factors such as: oceanographic and human mediated gene flow probably exert a large influence to the genetic structure of the studied populations.