Population genetic studies of genus Dicentrarchus reveal loss of genetic diversity in Egyptian waters

Abstract

Genus Dicentrarchus includes two closely related, and commercially important species, Dicentrarchus labrax and Dicentrarchus punctatus. These species have similar morphological features in early developmental stages, nevertheless, they have noticeably different growth rates. The molecular differentiation between these species is therefore of interest. Moreover, the assessment of genetic diversity within and among populations is a primary step towards investigating the population structure and proper conservation of wild stocks of these species in Egypt. For these purposes, in total 141 samples of both species were collected from three locations along the Mediterranean Sea (Maadia, Damietta and Bardawil Lagoon), in Egypt. The samples were sorted according to their external features into 87 D. labrax samples and 54 D. punctatus samples. A partial sequence of cytochrome oxidase subunit I (COI) gene was used to barcode the two species and to assess the genetic diversity of the collected samples. For population differentiation comparisons, D. labrax COI sequences representing six European countries (France, Spain, Sweden, Turkey, the UK and Germany) were retrieved from the NCBI database and used in the analysis. Among the Egyptian D. labrax populations, only six haplotypes were identified, with low haplotype diversity and nucleotide diversity (average Hd=0.2214, average π=0.001), suggesting possible reduction in population size. Eleven haplotypes were identified in D. punctatus populations, with moderate haplotype diversity and low nucleotide diversity (average Hd=0.469, average π=0.002). The recorded overexploitation of both species could be a reason for the reduced genetic diversity. The studied populations of both species exhibited low inter-population differentiation (average FST=0.035 and 0.065 for D. labrax and D. punctatus, respectively). However, high FST values were recorded between the Egyptian D. labrax populations and the European populations (FST=0.626–0.962, p<0.01) except for Turkey (FST=0.037, p<0.05). Special attention should be directed to proper protection and management of the existing diversity of the two Dicentrarchus species in Egypt.