Low microsatellite variation in Aphanius fasciatus from the Tarquinia Salterns

Abstract

1 - The Tarquinia Salterns (Latium, central Italy) provided the opportunity to analyse the impact of environmental stress on the genetic structure of the resident population of the killifish Aphanius fasciatus. Indeed, after the salt production ceased in 1997, the salterns have undergone habitat degradation due to lack of maintenance. The ecological restoration carried out from 2003 to 2006 reverted the environmental conditions to those of ten years before. 2 - The temporal variation of the gene pool of the population of A. fasciatus inhabiting the Tarquinia Salterns was investigated using microsatellite markers in samples collected in 1998 and 2003. The results obtained showed a low genetic variability and a genetic homogeneity of the population, which appears not divided in sub-demes. 3 - Microsatellites revealed a surprisingly low level of genetic variability when compared to allozyme data obtained in previous studies. This is likely due to a difference in the time of response of the two markers to environmental degradation. Microsatellites would lose genetic variability earlier and faster because of their usually high polymorphisms. Conversely, allozymes would be more resistant to genetic erosion, being moderately variable markers. 4 - Selection probably contributed in maintaining allozyme polymorphism, while microsatellites, being neutral markers, did not benefit from the action of selection and lost diversity earlier and more rapidly. Accordingly, the population appeared subdivided in distinct demes based on allozyme data but spatially homogeneous following microsatellites results.