New polymorphic microsatellite loci for population studies in the European anchovy, Engraulis encrasicolus (L.)

Biocomplexity in Populations of European Anchovy in the Adriatic Sea

The sustained exploitation of marine populations requires an understanding of a species' adaptive seascape so that populations can track environmental changes from short- and long-term climate cycles and from human development. The analysis of the distributions of genetic markers among populations, together with correlates of life-history and environmental variability, can provide insights into the extent of adaptive variation. Here, we examined genetic variability among populations of mature European anchovies (n = 531) in the Adriatic (13 samples) and Tyrrhenian seas (2 samples) with neutral and putative non-neutral microsatellite loci. These genetic markers failed to confirm the occurrence of two anchovy species in the Adriatic Sea, as previously postulated. However, we found fine-scale population structure in the Adriatic, especially in northern areas, that was associated with four of the 13 environmental variables tested. Geographic gradients in sea temperature, salinity and dissolved oxygen appear to drive adaptive differences in spawning time and early larval development among populations. Resolving adaptive seascapes in Adriatic anchovies provides a means to understand mechanisms underpinning local adaptation and a basis for optimizing exploitation strategies for sustainable harvests.

Coupling Demographic and Genetic Variability from Archived Collections of European Anchovy (Engraulis encrasicolus)

It is well known that temporal fluctuations in small populations deeply influence evolutionary potential. Less well known is whether fluctuations can influence the evolutionary potentials of species with large census sizes. Here, we estimated genetic population parameters from as survey of polymorphic microsatellite DNA loci in archived otoliths from Adriatic European anchovy (Engraulis encrasicolus), a fish with large census sizes that supports numerous local fisheries. Stocks have fluctuated greatly over the past few decades, and the Adriatic fishery collapsed in 1987. Our results show a significant reduction of mean genetic parameters as a consequence of the population collapse. In addition, estimates of effective population size (Ne) are much smaller than those expected in a fishes with large population census sizes (Nc). Estimates of Ne indicate low effective population sizes, even before the population collapse. The ratio Ne/Ne ranged between 10-6 and 10-8, indicating a large discrepancy between the anchovy gene pool and population census size. Therefore, anchovy populations may be more vulnerable to fishery effort and environmental change than previously thought.

Microsatellite markers to determine population genetic structure in the golden anchovy, Coilia dussumieri

Coilia dussumieri (Valenciennes, 1848) commonly called as golden anchovy, constitutes a considerable fishery in the northern part of both the west and east coasts of India. Despite its clear-cut geographic isolation, the species is treated as a unit stock for fishery management purposes. We evaluated 32 microsatellite primer pairs from three closely related species (resource species) belonging to the family Engraulidae through cross-species amplification in C. dussumieri. Successful cross-priming was obtained with 10 loci, which were sequenced for confirmation of repeats. Loci were tested for delineating the genetic stock structure of four populations of C. dussumieri from both the coasts of India. The number of alleles per locus ranged from 8 to 18, with a mean of 12.3. Results of pairwise F ST indicated genetic stock structuring between the east and west coast populations of India and also validated the utilization of identified microsatellite markers in population genetic structure analysis.

Isolation of novel microsatellite loci in the black goby Gobius niger and cross-amplification in other gobiid species (Perciformes, Gobiidae)

Twelve microsatellite loci were isolated from and characterized for the black goby Gobius niger. These loci were tested on a total of 48 individuals from two geographically distant locations (Orbetello and Cattolica) and the number of alleles ranged from two to 18, with expected (H(e)) and observed (H(o)) heterozygosities ranging from 0.042 to 0.941 and from 0.042 to 0.917, respectively. The loci described were used to cross-amplify other gobiid species belonging to Gobius, Zosterisessor, Lesueurigobius and Aphia.

Polymorphic microsatellite loci for the Japanese anchovy Engraulis japonicus (Engraulidae)

We isolated and characterized 14 polymorphic microsatellite loci in the Japanese anchovy (Engraulis japonicus) using a (GT)(13)-enriched genomic library. The numbers of alleles per locus ranged from 6 to 31, with a mean of 17.8. The observed and expected heterozygosities ranged from 0.180 to 0.949 and from 0.172 to 0.966, with means of 0.731 and 0.825, respectively. All 14 loci were in Hardy-Weinberg equilibrium and no significant linkage disequilibrium between loci pairs was detected. These microsatellite markers will be useful for analyzing the population genetic structure and gene flow of E. japonicus.