Genetic monitoring of brackish-water populations: the Mediterranean toothcarp Aphanius fasciatus (Cyprinodontidae) as a model

Abstract

The measurement of genetic variability and assessment of population genetic losses are important components of environmental management programs. Twenty-three natural populations of the Mediterranean brackish-water toothcarp Aphanius fasciatus were investigated using different statistical approaches based on genetic data at 13 polymorphic allozyme loci. In general, no differ- ences between values of within-population genetic variability estimates occurred. The Wilcoxon sign-rank test for heterozygosity excess due to a recent bottleneck was conducted on the array of populations. In addition, a qualitative descriptor of allele frequency distribution was used to infer bottlenecks. Only populations from the Orbetello lagoon and La Salina at Elba Island revealed sig- nificant heterozygosity excess under both the infinite allele model (IAM) and stepwise mutation model (SMM). A recent dystrophic crisis may account for the genetic loss detected in the population of A. fasciatus from the Orbetello lagoon, whereas exceptionally high predation pressure and/or the increased mortality rate created by local hydrological conditions could be responsible for the bottle- neck in the population at La Salina. Tests for bottlenecks have proved effective tools for genetic monitoring of A. fasciatus populations.