Fistularia commersonii (Teleostea: Fistulariidae): walking through the Lessepsian paradox of mitochondrial DNA

TheMediterranean Lessepsian migrations excite the interest of biologists who are devoted to inferring the effects of selection on
the genetic structure of immigrants. The bluespotted cornetfish Fistularia commersonii is an Indo-Pacific species that was first
recorded in the Levantine cost ofMediterranean, and within a few years, it rapidly expanded throughout the entire basin. Studies
on its genetic variability, performed via mitochondrial sequencing of theMediterranean specimens, suggest that a limited number
of mitochondrial lineages passed through the Suez Canal. However, nuclear markers provide a scenario, with a high genetic
variability among the Mediterranean F. commersonii migrants, along with the occurrence of haplotype sharing between the
Mediterranean and the Red Sea. The aimof this study was to enlarge the number ofMediterranean sites in order to evaluate if the
rapid expansion and different patterns of spread of F. commersonii in the basin could have led to a genetic structuring. The analysis
was carried out by sequencing mitochondrial D-loop I in individuals from Sardinia, Sicily, Tunisia, Lampedusa, Libya and
Lebanon. Sequences available from previous studies were included in the data set, allowing us to obtain a data set that likely
represents the entire distribution range of the species. Results suggest the possible occurrence of two mitochondrial lineages
involved in the Mediterranean invasion of F. commersonii, a bottleneck may have caused a loss in the genetic variation, leading to
the fixation of specific lineages as an adaptive response to the new environmental conditions.