MITOCHONDRIAL-DNA PHYLOGENY AND THE RECONSTRUCTION OF THE POPULATION HISTORY OF A SPECIES - THE CASE OF THE EUROPEAN ANCHOVY (ENGRAULIS-ENCRASICOLUS)

Analysis of mitochondrial DNA restriction fragment length polymorphism in European anchovy (Engraulis encrasicolus) revealed a large number of mitotypes that form two distinct clusters (phylads). Phylad A consi sts of one common mitotype and many rare secondary mitotypes that are one mutational step removed from the main type. Nucleotide diversity a nd number of homoplasious changes are low. Phylad B has a complex patt ern of mitotype connectedness, high nucleotide diversity, and a large number of homoplasious changes. It is suggested that the two phylads e volved in isolation from each other and that present coexistence is th e result of a secondary contact. Moreover, phylad A has a ''star'' phy logeny, which suggests that it has evolved in a population that experi enced a drastic bottleneck followed by an explosion of size. Phylad A is practically the only phylad present in the Black Sea, with its freq uency dropping to 85% in the northern Aegean, and to 40% in the rest o f Mediterranean and the Bay of Biscay. The Black Sea is, therefore, th e most likely place of origin of phylad A. Molecular data are consiste nt with a population bottleneck in the Black Sea during the last glaci ation event and a subsequent exit of phylad A with the outflow into th e Aegean following the ice melting. Phylogenetic analysis of anchovy m tDNA provides a reconstruction of population history in the Mediterran ean, which is consistent with the geological information.