Population structure of anchovy Engraulis encrasicolus L. in the Mediterranean Sea inferred from multiple methods

Population structure of anchovy, Engraulis encrasicolus L., in the northern Mediterranean was investigated using multiple methods. Variation in body shape, otolith shape and growth was investigated in samples from the central Aegean and Ionian Seas. Intron length polymorphism from nuclear DNA, and mitochondrial DNA variation was investigated for samples from these basins, as well as northern Adriatic (ADR) and Gulf of Lions (LION). Two lineages (clades) of mtDNA that co-occur in the populations of anchovy throughout the region were compared with respect to growth, body shape, otolith shape, and intron variation, to check for any reproductive isolation within areas between the clades. The two clades were not different in any of the investigated parameters and appear to be completely crossbreeding. There were significant differences among areas with regard to mtDNA clade proportions, nuclear allele frequencies, body shape and otolith shape, indicating that several reproductively isolated populations of anchovy exists in the northern Mediterranean. There was an overall fair to good agreement between population structures inferred from the different classes of markers. The mitotype variation indicated a larger population differentiation than the two nuclear DNA loci, which may be related to the uniparental transmission and the lack of recombination of mtDNA.