Genetic population structure, gene flow, and evolutionary history of selected ornamental fish in the Red Sea

Abstract

The ornamental fishery is expanding rapidly in the Red Sea, and concerns about the possibility of overexploitation were raised. Marine protected areas (MPAs) were addressed as a potential solution to prevent overexploitation. However, the sources of stock recruitment are not well understood. This thesis aims to reveal the genetic population structure and the demographic connectivity in the endemic fish species of the Red Sea Larabicus quadrilineatus, and in the two common fish species Chromis viridis and Pseudanthias squamipinnis. The fish samples were obtained from five locations in the Red Sea. For comparison, additional samples of the two common species were obtained from two locations in the Indo-Malay Archipelago. Partial sequence of the mitochondrial control region was used as a molecular marker in the three studied species. The studied species exhibited high genetic diversity as inferred from the haplotype and nucleotide indices. Analysis of molecular variance (AMOVA) detected significant genetic variation between northern and central/southern populations of L. quadrilineatus (ΦCT = 0.01; P < 0.01), and between the populations in the Gulf of Aqaba and the Red Sea proper of P. squamipinnis (ΦST = 0.02; P < 0.01). In addition, AMOVA detected significant genetic variation between the Red Sea and the Indo-Malay Archipelago for both C. viridis (ΦCT = 0.462; P < 0.001) and P. squamipinnis (ΦST = 0.78; P < 0.001). Migration analysis in the Red Sea revealed (1) higher migration into the Gulf of Aqaba for all species; (2) higher northward migration for C. viridis and L. quadrilineatus; and higher southward migration in the Red Sea proper for P. squamipinnis. A significant relationship between the genetic versus the geographic distances was shown only for L. quadrilineatus, and as a consequence the mean larval dispersal distance based on the isolation-by-distance model was estimated to be between 0.44 and 5 km. Estimates of the effective population size were the highest (1) in Hodeidah (southern Red Sea) for both L. quadrilineatus and C. viridis; and (2) in Tor (northern Red Sea) for P. squamipinnis. The results in this thesis were discussed in relation to the oceanographic factors and the biological features of the studied fishes. The historical event Last Glacial Maximum proved its influence on the population demographic history and the currents effective population size of the studied species. In order to enable a sustainable ornamental fishery on the studied species in the Red Sea, the results of this thesis suggest that (1) populations in the Red Sea should be managed as one stock for C. viridis; (2) populations of L. quadrilineatus northern and southern Red Sea should be managed as two stocks; and (3) populations in the Gulf of Aqaba and in the Red Sea proper should be managed separately for P. squamipinnis. The rather low larval dispersal distance of about 5 km needs to be considered in the design of MPAs to enable connectivity and self-seeding in L. quadrilineatus.