All these environmental features are known to modify the temperature regime of the surface waters in the Sicilian anchovy habitat. Moreover, the main water masses present in this channel, connecting the western and the eastern basins of the Mediterranean Sea, are characterized by a complex multi-scale thermohaline circulation, driven by ocean currents, wind effects, and mesoscale activity. In the Mediterranean basin, within a latitudinal range of about 10° (45°-35°N) the annual average sea surface temperature goes from 15☌, in the northern Adriatic to 20☌ in the Strait of Sicily or Sicilian Channel between the Sicilian and the North African coasts. detected positive selection in a single codon of the mitochondrial cytochrome b (cytb) gene in clade B, geographically correlated with environmental temperature.
demonstrated that the high mobile nature of anchovies allowed them to escape the adverse temperatures during the last glacial maximum without losing genetic diversity. More specifically, studies by Silva et al. Thus, this species has been considered an ideal organism to study both the adaptative behaviour of small pelagic fish under different environmental conditions, and to understand the effect of quaternary climatic fluctuations on the distribution of marine organisms. European anchovy population dynamics and distribution patterns are known to be strongly dependent on the environment. It has also been suggested that the two mtDNA clades can also occur in simpatry, and that temperature seems to have shaped their relative frequency, as a result of range expansion and post-glacial secondary mixing. and Grant pointed out the role of climate change during Pleistocene glaciations, suggesting that the two phylads evolved in isolation in an Atlantic refugium and in the Mediterranean, respectively. Clade B prevails at the northern and southern high latitudes with frequencies decreasing towards the tropics, whereas clade A is present with higher frequencies in the tropical and subtropical areas. The distribution of these haplogroups differs among natural populations but shows a constant proportion in each population, over time. In particular, mtDNA, SNPs and nuclear intron markers have all supported the presence of two sympatric clades, named phylads or haplogroups A and B. In the Atlantic Ocean and the Mediterranean Basin, ten genetically differentiated European anchovy populations have been identified by surveys of the variability of the mitochondrial control region with implications for the management of fishery stocks. encrasicolus using allozymes, mitochondrial DNA (mtDNA) and nuclear markers. Molecular studies described a complex genetic structure of E. In the last twenty years a number of scientific studies have focused on the detection of genetic population structure in this commercially important species, through morphological and molecular analyses. Its biology has received particular attention due to the commercial interest of its fisheries. The European anchovy, Engraulis encrasicolus (Linnaeus, 1758), is a clupeoid pelagic species widely distributed in the Mediterranean, Black and Azov Seas, Eastern Atlantic coastline from Norway to Angola, and around the tip of southern Africa. The selection tests applied to the COI dataset revealed that codon 116 was not under positive selection, that seven amino acid changes were under purifying selection, and that two amino acids were under episodic positive selection. The two haplogroups A and B were also discriminated by the variable number of TACA elements at the 5’-end of the mitochondrial CR. All COI sequences of haplogroup A had an amino acid sequence with alanine in this position, while serine was present in the same position in haplogroup B. The COI sequence analysis identified a non-synonymous transversion (T to G) at position 116 of the translated sequence, resulting in an amino acid change. Both CR and COI markers consistently identified two haplogroups. In both populations, the two markers revealed the presence of two main haplogroups, A and B, already detected in previous investigations of different classes of molecular markers. encrasicolus from four localities in the central Mediterranean. In this study, the mitochondrial Control Region ( CR) and the Cytochrome Oxidase I ( COI) mitochondrial gene were analyzed in 74 specimens of E. The European anchovy, Engraulis encrasicolus, is currently one of the principal target species for commercial fisheries in Europe.
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